We consume different foods according to its nutritional benefits for us mainly,this nutritional density can not recognized well from the visual appearance ,but studies conducted using agrotechniques aid to estimate this criteria gave us a clear imagination about what nutritions available and it,s amount in any species and cultivar fruits .

I think it's colour and appearance....

Dr. Kumar has highlighted very important question in plant nutrition. The researchers participation is appreciable. The visual symptoms indicate the nutritional pattern of plants but still there are hidden losses if certain element if these are deficient in supply/availability.

You could try to cook and apple and a citrus in the oven, add a small bowl with oven melted chocolate with crushed pepper and on top of it, drink water, coffee or tea and your breakfast is rich and takes enough time for a slow breakfast. It also allows one to keep track of the food diary, it is necessary to eat !!

I think clients usually dwell on the colour and size (Visual Appearance) of fruits and vegetables in judging their nutritional value. There must be intensive education on how to determine the nutritional values of fruits and vegetables from the perspective of clients.

Due to the archetypal roles fruits and vegetables play in our lives, enough sensitization on how to distinguish the good and healthy ones from the bad ones must be espoused by food scientists globally. Best regards

By displaying the material and its quality

visual appearance is the only way to determinate vegetables and fruit nutritional value by consumers. educate them in how to grow food at home using nutrient dense growing practices, and ensuring agricultural practices that increase the nutritional density of food are the most important for this subject.

nutritional quality of fruits and vegetables have useful amount of natural minerals and vitamins; low calories and absence of cholesterol.

Their physical appearance, color, and odor are what I use to determine vegetables and fruit quality.

The origin and proximity are important, I do not trust imported fruits and vegetables coming from distances of thousands of miles away, this will affect their freshness, quality and nutritional value.

Agreed with the comments by all the contributors. In present day context, additionally it is most important that the fruits and vegetables are safe, containing heavy metals or pesticide residues below MRL. Otherwise, the goods for which they are consumed would be nullified by the impact of such undesired levels of residues/heavy metals.

Usually, the nutritional qualities of fruits & vegetables can be accessed visually from the colour of such fruit/vegetables. For most fruits & vegetables, the greener the better. Slight or conspicuous change in colour could depict deficiency of essential nutritional elements.

You can choose either qualitative and /or quantitative data for consumer perspective. You can use scales (1-5) on color, fragrance, and texture for qualitative data by preparing test panels. The most common parameters for quantitative data to determining the quality of fruits are firmness (Mitutoyo Model ID-C125EB, Corp.; Aurora, ILL.), pH, Total soluble solids, juice percentage (for juice content determination). The later are the better as they are objective data.

Please give a thought to this wonderful work...why dont we stress on this issue...

J Am Diet Assoc. 2005 Dec;105(12):1881-7.

A nutrient density standard for vegetables and fruits: nutrients per calorie and nutrients per unit cost.

OBJECTIVES:The Dietary Guidelines for Americans 2005 recommended that consumers give priority to nutrient-dense foods, those that contain substantial amounts of key nutrients in relation to the dietary energy they provide. This study developed a scoring system to estimate the nutritional adequacy of vegetables and fruits, on a per weight, per calorie, and per unit cost basis.

DATA:We used a French national food composition database for 637 foods, including 129 vegetables and fruits. Mean national retail prices were obtained for each food.

METHODS:The nutrient adequacy score was defined as the mean of percent daily values for 16 nutrients, based on 100 g of food. The nutrient density score and the nutrient-to-price ratio were the mean of percent daily values for 16 nutrients, expressed per 100 kcal and per 1 euro of food, respectively. Relationships between energy density of vegetables and fruits, nutrient adequacy score, nutrient density score, and nutrient-to-price ratio were tested using linear regression.

RESULTS:Energy density and nutrient density score were negatively correlated, confirming the widely accepted notion that energy-dense foods tend to be nutrient-poor. As expected, fruits and vegetables had the highest nutrient density score because they were nutrient-rich in relation to their low energy content. They also had a relatively high nutrient-to-price ratio, showing that they provided nutrients at a reasonable cost when compared with other foods.

CONCLUSIONS:Foods ranked differently when nutritional adequacy was calculated per weight (nutrient adequacy score), per calorie (nutrient density score), or per unit cost (nutrient-to-price ratio). The present results showed that although fruits and vegetables are an expensive source of dietary energy, they provide key nutrients at a reasonable cost.

What are available options of nutritional rating systems of different fruits and vegetables..?

Nutrient density identifies the proportion of nutrients in foods, with terms such as nutrient rich and micronutrient dense referring to similar properties. Several different national and international standards have been developed and are in use ( Nutritional rating systems ). These are methods normally used:

Glycemic index :Glycemic index is a ranking of how quickly food is metabolized into glucose when digested. It compares available carbohydrates gram for gram in individual foods, providing a numerical, evidence-based index of postprandial (post-meal) glycemia. The concept was invented by Dr. David J. Jenkins and colleagues in 1981 at the University of Toronto.The glycemic load (GL) of food is a number that estimates how much the food will raise a person's blood glucose level after eating it.

Guiding Stars:Guiding Stars is patented food rating system that rates food based on nutrient density using a scientific algorithm. Foods are credited for vitamins, minerals, dietary fibre, whole grains, and Omega-3 fatty acids, and debited for saturated fats, trans fats, added sodium (salt) and added sugar. Rated foods are marked with tags indicating one, two or three stars. The program first launched a Hannaford Supermarkets in 2006, and is currently found in about 1,900 supermarkets in the US and Canada. Guiding Stars has also expanded into public schools, colleges and hospitals.

The evidence-based proprietary algorithm is based on the dietary guidelines and recommendations of regulatory and health organizations including the US Food and Drug Administration, the US Department of Agriculture, and the World Health Organization. It was developed by a scientific advisory panel composed of experts in nutrition and health from Dartmouth College, Harvard University, Tufts University, University of North Carolina and other colleges.

Nutripoints: Nutripoints is a system for rating foods on a numerical scale for their overall nutritional value. The method is based on an analysis of 26 positive (such as vitamins, minerals, protein, fiber) and negative factors (such as cholesterol, saturated fat, sugar, sodium) compared to the calories in the food. The overall Nutripoint score of the food is the result. The higher the value, the more nutrition per calorie (nutrient density) and the least negative factors in the food. Thus, the higher the Nutripoint score, the better the food for overall health. The system rates 3600+ foods including basic foods like apples and oranges, fast-foods, and brand-name foods.

Nutripoints was developed by Dr. Roy E. Vartabedian (a Doctor of Public Health) in the 1980s and was released to the general public in 1990 with his book, "Nutripoints," published in 13 countries and 10 languages worldwide. The food rating system is part of an overall program designed to help people measure, balance, and upgrade their diet's nutritional quality for overall health improvement and well-being.

Nutrition iQ: The Nutrition iQ program is a joint venture of the Joslin Clinic and multi-banner supermarket operator Supervalu. The labeling system consists of color-coded tags denoting a food product's superior status with respect to attributes such as vitamin and mineral content, fiber content, 100% juice content, Omega-3 or low saturated fat content, whole grain content, calcium content, protein content, low or reduced sodium content and low or reduced caloric content. The first phase of the program launched in 2009 covering center store food products, with coverage of fresh food departments rolling out in 2011.

POINTS Food System : Weight Watchers developed the POINTS Food System for use with their Flex Plan. Healthy weight control is the primary objective of the system. The system is designed to allow customers to eat any food while tracking the number of points for each food consumed. Members try to keep to their POINTS Target, a number of points for a given time frame. The daily POINTS Target is personalized based on members' height, weight and other factors, such as gender. A weekly allowance for points is also established to provide for special occasions, mistakes, etc.

Naturally Nutrient Rich (NNR: Developed by Adam Drewnowski, University of Washington, NNR[7] "is based on mean percentage daily values (DVs) for 14 nutrients in 2000 kcal food, can be used to assign nutrient density values to foods within and across food groups. Use of the NNR score allows consumers to identify and select nutrient-dense foods while permitting some flexibility where the discretionary calories are concerned."

ReViVer Score: Developed by ReViVer, a nutritionally-oriented restaurant in New York City,[8] the ReViVer Score expresses the nutrient density of menu items from a variety of fast food and casual restaurants, based on the amount of 10 nutrients (Vitamins A, C, and E, folate, calcium, magnesium, potassium, iron, fiber, and omega-3 fats) per calorie. A score of 100 indicates that the meal provides at least 100% of the recommended daily intake for all ten nutrients, proportionate to the energy (calorie) content of the meal.[9] The score allows consumers to compare the nutritional quality of various restaurant offerings with similar calorie content.

Systems used in the past

Smart Choices Program[edit]

Launched late in 2009, the Smart Choices Program (SCP)[10] was a rating system developed by a coalition of companies from the food industry. The criteria for rating food products used 18 different attributes, however, the system had varying levels of acceptability based on 16 types of food which allowed for wide discretion in the selection of foods to include in the program. The program was discontinued in October 2009 after sharp criticism for including products such as "Froot Loops", "Lucky Charms" and "Frosted Flakes" as Smart Choices. As a consequence of the backlash from the program, General Mills announced on December 10, 2009 that it would reduce the amount of sugar in many of its cereal brands.

Announcement of Closure : On August 19, 2009, the FDA wrote a letter to SCP manager, saying: "FDA and FSIS would be concerned if any FOP labeling systems used criteria that were not stringent enough to protect consumers against misleading claims; were inconsistent with the Dietary Guidelines for Americans; or had the effect of encouraging consumers to choose highly processed foods and refined grains instead of fruits, vegetables, and whole grains. SCP was suspended in 2009 after the FDA's announcement that they will be addressing both on front-of- package and on-shelf systems. SCP Chair Mike Hughes said: "It is more appropriate to postpone active operations and channel our information and learnings to the agency to support their initiative."

Claimed Rigor : Smart Choices Program "was developed by a coalition of scientists and nutrition educators, experts with experience with dietary guidelines, public health organizations, and food manufacturers in response to consumer confusion over multiple front-of-the-package systems based on different criteria. Representatives from different government organizations acted as observers. The process of developing the program was facilitated by the nonprofit Keystone Center, an organization that develops consensus solutions to complex health and social policy changes. The nutrition criteria for receiving the SCP icon are specific for product category by indicating "smarter" products within that category. A calorie indicator noting calories per serving and servings per package accompanies the SCP icon to remind consumers that calories do count, even for smarter food choices. For a product to qualify, it first has to be below the threshold for "nutrients to limit" and then (in most cases) it must be above the threshold for one or more nutrients or food groups to encourage. The criteria are based on the 2005 Dietary Guidelines and other consensus science and are transparent and available on the SCP website."

Thank you Dr. Kumar for giving information about Nutripoints.

* How important is the nutrient density of fruits and vegetables?

importance in generating blood cells

* Can we judge the nutrient density of fruits and vegetables from their visual appearance?

No

* What are those criteria to evaluate the nutritional quality of fruits and vegetables?

can be seen in articles

* Is there any nutrient density standards for different fruits and vegetables?

Yes. Definitely there will be some standards

* How does different agro techniques aid in improving the nutrient density ?

in right farmings

These quality literatures are revelations to our colleagues..so informative..Abhishek..

Some fascinating stuff on the issue ...to be read by one and all following this question..

Evaluation of nutritional value by consumer depend mainly on it,s appearance ,color,and taste ,furthermore many peoples depend in their choice for vegetable and fruits on the healthy benefits of fresh consuming foods and low oils content and low calories resulted from digestion of these fresh foods..

As Ali Alhayany said color and taste and appearance. Maybe I was not making myself clear Anoop and I apologize for that.

Unless there is a try before you buy policy in place, as is the case with some supermarkets and vendors that I have had the experience of working with for quite some time I must add, I can say mostly people choose fruit on appearance and feel, but also in terms of whether they know where it was farmed and then how much they know about that farming process itself, if it is organic produce people want to know even more. But nowadays supermarkets are trying to promote local produce too, and in Australia consumers are choosing to buy Australian produce because they know that it is fresher and comes from farms owned by Australians, I think the same can be said for most of the world, except for countries who have to import the majority of their produce.

One can not just assume that fruit is not nutritional because it doesn't look appealing and this stigma sees billions of tonnes globally thrown away each year because the appearance will not make the supermarket shelf.

So my answer is look first and then feel and then taste :) but this assessment is based on my experience and knowledge of the farming processes and the consumer choices that also dictate what is available too. Not to mention the economics and commerce of the fruit and vegetable industry is not only driven by the consumer.

Please have a look

Good material shared by Raj for the researchers.

Fruit and vegetable from nutritional point are rich in fiber. this fiber has many health benefit for person in his life. Fiber control body weight, blood glucose, cholesterol, in addition avoid constipation, I thing it has functional role in metabolism because it contains vitamins that work as co-enzyme, and minerals which act as co-factor in metabolism of the nutrient.

Highly useful pdf(s)

Yes, nutritional changes occur during freezing of fruit and vegetables, these must be kept in mind.

Interesting idea Dear Dr. Anoop Kumar Srivastava.

Consumers are very sensitive when buying fruits and vegetables. Before buying the fruits and vegetables, they evaluate through color, freshness, texture of fruit, cleanness from different pest attack, smell (aroma and others), size, test and sometimes organicity. As these are some of the major parameters considered by the consumers, it is good to consider them as as a some of the quality parameters for fruits and vegetables for addressing the needs of the consumers.

Dear Raj! It is very useful pdf, thank you

It is true that all fruits are healthy and have their own particular benefits, however some fruits contain more sugar (fructose) than others. Although this natural source of sugar is not as harmful as candy, it can not only cause weight gain but in high amounts facilitate the onset of other health conditions and chronic disease.

According to Dr. Mercola, here are the healthiest fruits along with their nutritional value:

Coconut

• Lauric acid, the major fatty acid from coconut fat, has antiviral, antibacterial, and antiprotozoal functions.
• May help to normalize body lipids, thereby protecting against alcohol damage to the liver and improving the immune system's anti-inflammatory response
• Coconut oil is one of the healthiest oils you can consume

Berries

• Contain powerful phytochemicals such as ellagic acid that provide antioxidant protection, as well as directly inhibit the DNA binding of certain carcinogens
• Excellent source of vitamin C, carotenes, zinc, potassium, iron, calcium, and magnesium
• High in fiber
• Low in sugar

Olives

• Contain polyphenols that help fight cancer and have an anti-inflammatory effect
• Rich in monounsaturated fat

Papaya

• Rich in antioxidants like carotenes, vitamin C, and flavonoids
• Contains B vitamins, vitamin E, folate, and fiber
• Rich source of minerals, potassium, and magnesium
• Useful for digestion (papaya contains papain, an enzyme that helps with digestion by breaking down proteins)
• May provide protection against caner
• Provides support for the immune system
• Has anti-inflammatory effects

Avocado

• Excellent source of raw fat, which many Americans are deficient in
• Rich in monounsaturated fat, which is easily burned for energy.
• An avocado has more than twice as much potassium as a banana.
• Good source of folate, dietary fiber, vitamin C, vitamin E, riboflavin, and vitamin B6

Mango

• Rich source of carotenoids, and vitamins B and C
• Contains calcium, iron, and potassium
• Good source of phosphorus, selenium, folate, and zinc
• Contains some protein and amino acids

Pineapple

• Contains an enzyme, bromelain, which aids digestion, reduces inflammation and swelling, and may have anti-cancer effects
• Rich in antioxidants like vitamin C
• Provides immune support
• Excellent source of manganese, thiamin, and riboflavin, which are important for energy production

Guava

• Excellent source of vitamin C, lycopene, carotenoids, folate, potassium, fiber, calcium, and iron
• Consumption of guava fruit may reduce LDL (“bad”) cholesterol
• Has anti-microbial properties that may fight bacteria such as Staphylococcus aureus and beta-streptococcus group A.
• Guava is sometimes used as a treatment for diarrhea by natural medicine workers in the tropics

Kiwi

• Excellent source of antioxidant vitamins C and E, and beta-carotene
• Rich in phytonutrients that appear to protect human DNA from free-radical damage
• Good source of fiber, potassium, magnesium, copper, and phosphorous

Interesting question and answers, following.

Answer of Beemnet is highly interesting.

Interesting question .... useful discussion

Green houses allow you to grow plants for a longer season than you could outside, or in a colder climate. The fruits grow more quickly and come to ripeness sooner than they would outside, but if you were to analyse those fruits for nutritional content, there would be no significant difference between those and the ones grown outside, all other things being equal. All other things being soil type, variety of the plant, access to water, use of pesticides etc.

Vegetables that grow more rapidly will have lower “soluble solids” which contain a lot of the vitamins, and more water. They can lack flavor, like greenhouse tomatoes. The stronger the flavor, the more vitamins.

Quality parameters

Quality attributes of fruits and vegetables such as appearance, colour, aroma, taste drive the decision of consumers to buy a product.

In the past high quality standards were mainly imposed by retailers (e.g., long shelf-life, colour, texture, shape) and less on the consumers’ side. Currently, consumers are demanding fresh fruits and vegetables not only appealing (bright colour and perfect shape) and convenient (‘ready to eat’, ‘eat me’ concepts), but tasty and with significant nutritional value (with high vitamin and antioxidant contents). To meet these consumers’ needs changes in the current organization of the fresh supply chain are necessary.

Quality assessment

Keeping the quality of any fresh commodity starts with growing, producing and selecting a good quality product. Wageningen Food & Biobased Research offers quality assessment at different stages of the fresh supply chain: grower, transport and retail. But also at different levels: edible, nutritional, external and internal quality. By assessment of the right quality at harvest or optimal maturity stage (e.g., based on dry matter content, °Brix, colour, shape, etc) for a certain target market, postharvest technologies can be optimized and shelf-life extended by monitoring the quality throughout the whole supply chain either by destructive and or non-destructive techniques.

Keeping quality throughout the supply chain

Our focus in research is understanding the initial quality and the quality development during the complete supply chain by using postharvest physiology and technology knowledge in a smart way, which guarantees satisfaction of all key players of the chain (growers, retailers and consumers).

It is good to use also advanced technologies on:

• General quality assessment of produce based on destructive and non-destructive techniques (e.g., colorimeter, NIR, firmness);
• External and internal assessment of disorders;
• Flavour and nutritional quality assessment (e.g., aroma profiles based on GC-MS measurements and sensory panels; vitamin C, total antioxidant determinations, etc);
• Initial quality biomarkers (at different cellular levels: genes, proteins and metabolites).

The basic principles of total quality can be summarized in the following way:

• The consumer is always first
• Each operation is part of a process
• Quality improvement never ends
• Quality is made, not controlled
• Prevention of quality problems is made through planning.
• The desired product should be obtained at the desired moment. Post harvest handling should be appropriate to reach the desired market under the desired conditions.

Total quality in fruits and vegetables

The concept of quality as a way to differentiate products has been recognized for years. As local or regional trade internationalizes, quality consolidates as the main competitive tool for excellence, reinforcing the need to establish standards to separate quality into categories or degrees, as well as to define the limits of allowed defects. Nowadays, domestic and international trade of fruits and vegetables is regulated by quality standards in most countries, providing a common language among the different participants of the production-commercialization-consumption chain. Standards are also the legal framework to settle commercial disputes and are useful as a basis for reporting on market prices as prices only can be compared between the same quality category.

The quality system established by the standards is known as "Inspection for quality" where representative samples at the final stage of preparation for the market should fulfill the specified limits and their tolerances. Although it is easy to apply, it has, at least, two big disadvantages: firstly, they are not totally adapted to highly perishable products where quality varies continually. Secondly, its application does not improve the quality of the product, it only separates in degrees the quality that comes from the field.

At the same time that quality standards developed and were applied, new ideas began to be conceived by industry. Firstly, it became evident that a systematic and preventive approach was much more effective and economic to improve quality than the elimination of the faulty units at the end of the line, when the production and packaging costs had already happened. Secondly, it became clear that the quality concept extends beyond the product itself, since it is affected by the systems and procedures involved in the production and preparation for the market. Finally, the consumer's opinion begins to be more and more important. It is no longer sufficient for a product to be technically perfect and produced in an economically profitable way, it is also necessary to satisfy the consumers'expectations of quality.

The application of statistics to control the variability of the different units in the production lines gave birth to the system called "Quality control" or "Statistical Quality Control", which was adopted by most manufacturing companies in the first half of the 20th century. This method or system essentially provides the analytic tools for monitoring the production process and for taking measures when variability exceeds certain limits considered as normal. Its application improves the quality of the process contributing greatly to improve the quality of the product. They are tools that can be applied at the fruit and vegetables packinghouse level.

This system was transferred to Japan after World War II where it evolved into what today is known as "Total Quality Management" or simply "Total Quality". Total quality is today the most complete conceptual framework to assure quality to which each person or activity within the production process is committed, aiming at zero defects and customer's complete satisfaction, even going beyond his/her expectations. At the same time that TQM was developed, the concept of "Quality Assurance" was coined in Europe. Its scope is slightly narrower than TQM, but a lot easier to implement and probably better adapted to fruit and vegetables. It is defined as all those planned and systematized actions necessary to guarantee that the product or service will satisfy the requirements of quality. It usually requires the fulfillment of certain rules, protocols, or standards developed specifically and with a certification by an independent company authorized to grant it. The ISO system is probably the best known and within it the series 9000.

It is also appropriate to mention the HACCP(Hazard Analysis Critical Control Points) system, designed specifically to guarantee that food is not exposed to any type of contamination that could put health at risk. Today, this method is recognized internationally as the logical and scientific tool for all food quality systems. It is also preventive in nature and the key element is the identification of the critical points, within the process, where quality should be controlled to prevent, eliminate or reduce to acceptable levels all possible safety risks. The HACCP system is required today in the USA and other countries to import meat, fish, eggs, and other foods. Up to now, it is not required for fruits and vegetables, although different export countries are already implementing it to assure a superior quality of their products. The logic of the HACCP can be applied to the detection of other defects of quality.

Although all these systems have their origin in industry, their application extends to other sectors. Agriculture, and particularly the production of fruits and vegetables, is now incorporating many of the methods and ideas conceived by the industrial sector because the basic principles are not only applicable but also recommendable for highly perishable products where quality deteriorates quickly. Several export companies have implemented the HACCPtogether with the ISO 9002 certification, which guarantees food safety within a system of quality assurance. Akey concept is that quality systems are not mutually exclusive but rather they overlap widening the application approach, extending beyond the product itself and embracing the preparation process, inputs, suppliers and intermediaries, besides the incorporation of the feedback from the client or consumer for its continuous improvement.

Obtaining a product of quality

Producing a quality product begins well before planting the seed. Soil selection and preparation, its fertility and irrigation aptitude, weed control and crop rotations, variety selection and other decisions have an influence on the quality of the product. In the same way, quality is affected by the climatic conditions during the growing period, as well as irrigation, fertilizations, control of pest and diseases and other cultural practices. Harvest is the end of cultivation and the beginning of post-harvest actions during which preparation for the market, distribution, and sale take place.

Fruits and vegetables are highly perishable products and before being detached from the mother plant all demand water and nutrients. Once harvested, however, they depend on their reserves to continue living. Respiration, transpiration and the continuous changes taking place determine the internal and external quality. Deterioration rates depend on the type of product, growing conditions and other factors, but mainly on the conditions in which the produce is maintained after harvest such as temperature, relative humidity, movement and composition of the air, etc. Post harvest changes can only be delayed within certain limits and thus preparation for the fresh market should be quick and efficiently performed to avoid quality losses.

Besides their natural deterioration, rots and physiological and mechanical injuries already described in previous chapters, are also responsible for loss of quality. Post-harvest losses due to microorganisms can be severe, particularly in warm climates with a high relative humidity. Rotting produce contaminates the rest and under these conditions ethylene production is stimulated accelerating the rate of deterioration.

Most of the fungi and bacteria that attack fruits and vegetables after harvest, are weak pathogens and they mainly invade tissues through wounds. (Wills, et al., 1981). Injuries produced during handling provide numerous entrance routes to these pathogens although some of them are able to invade healthy products. Unripe fruits are usually more resistant to pathogen attack. It is also possible that infection occurring at the immature stage shows up later, when the natural defenses are weakened by the ripening process (Dennis, 1987). A good disease control program at field level reduces the source of inoculum and the risks of infections after harvest facilitating the control of post harvest diseases. Also, careful handling during harvest and packing operations reduces the physical damage that facilitates the establishment of microorganisms. Controlling temperatures to which produce is exposed is one of the main tools to control post harvest diseases since it diminishes the metabolic activity of the microorganisms and, by reducing the rate of the ripening process, the natural defenses of the product are kept high. Controlling the relative humidity, particularly to avoid the condensation of water on the product, as well as controlled atmospheres is also useful in the control of post-harvest diseases.

Safety

Fruits and vegetables should be attractive, fresh, nutritive and with a good appearance and presentation. Besides these characteristics, their consumption should not put health at risk. The consumer has no way to detect the presence of dangerous substances on food and he/she depends entirely on the seriousness and responsibility of all the members of the production and distribution chain. Necessarily, he/she has to trust them, in addition to the usual precautions of washing, peeling and/or cooking the product before consuming it. However, this trust is very volatile and any suspicion about safety has a tremendous impact at consumer level. Among the most relevant examples it is worth to mention the epidemic of cholera in the 90s in Latin America that reduced the consumption of vegetables in many countries of the region for almost one year. Another example may be the two grapes with dangerous residues detected in the 80s in an entrance port of the USA, which severely affected Chilean exports. Also about that time, the Alar (daminozide, a growth regulator used to control fruit set) scare considerably diminished the consumption of apples in the United States.

Food safety is the absence of substances dangerous for health and particularly in fruits and vegetables, the presence of pesticide residues on the product has been the main concern for consumers. However, there are many other contaminants potentially as dangerous such as the presence of pathogenic microorganisms, mycotoxins, heavy metals, and others.

As fruits and vegetables are consumed fresh and are many times not peeled, all organisms pathogenic to humans which are carried on their surface constitute a potential danger. The hygienic and sanitary measures to reduce the food risk have already been described in the previous chapter. Bacteria, like Shigella spp., Salmonella spp., Aeromonas spp., Escherichia coli, Listeria monocytogenes and the toxins produced by Clostridium botulinum and others, have been identified as responsible for illnesses associated with the consumption of fruits and vegetables. The Hepatitis A virus has been detected on produce as well as parasites like Entomoeba histolyca, and Giardia lamblia.

Agrochemicals are one of the tools that man has used to satisfy the growing need for food. They are the herbicides, insecticides, fungicides, fumigants, rodenticides, growth regulators, waxes, disinfectants, additives and all other products of a chemical nature used during production or post-harvest handling. Their residues have always been a major concern, although the advances in chemistry and biochemistry, the better understanding of ecology as well as pests and diseases, and the growing use of non-chemical control methods, have made the present world a much safer place. Today's agrochemi-cals are less toxic and persistent, their degradation products are generally innocuous and better laboratory methods have been developed for their detection. Additionally, there is a greater consciousness about their use, waiting times, doses, etc.

Each country has its own legislation in terms of the Maximum Residue Levels (MRLs) within the framework of the Codex Alimentarius Commission or other international organizations. An MRLor tolerance is the maximum concentration of pesticide residue allowed resulting from its application according to correct agricultural practices.

Agrochemical use should be within the Good Agricultural Practices framework to guarantee maximum safety and to minimize risks to the consumer's health. Specific products should be used to control pests or diseases following the manufacturer's indications, particularly those refering to crops on which they can be used, as well as minimum waiting times between application and harvest.

Other health hazards are the presence of nitrates in leafy vegetables, oxalates in some species and heavy metals accumulation, particularly when sewage is used as fertilizers or organic amendments. Some toxicity may exist in some natural compounds produced by the crop itself or by the fungi that colonize its surface like the micotoxins.

Nutritive value

From the nutrition point of view, fruits and vegetables are insufficient to satisfy daily nutritional requirements, essentially because of their low content of dry matter. They have a high content of water and are low in carbohydrates (excepting sweet potatoes, potatoes, cassava, and other underground organs), proteins (except for legumes and some crucifers) and lipids (except avocados), but they are, in general, a good source of minerals and vitamins. Different countries have made tables of recommended daily consumption, the best known being probably the U.S.R.D.A. (United States Recommended Daily Allowances). These tables are only for reference and they indicate the capacity of foods to satisfy the daily needs for certain nutrients. The conditions of cultivation, varieties, climate, and preparation affect the actual content of nutrients.

Dietary fiber can be defined as the vegetable portion that cannot be degraded by the enzymes of the human digestive tract although its components are anaerobically metabolized in variable proportions by the colon microflora. The optimum daily ingest for a healthy adult is 25 to 30 grams and the contribution of certain fruits and vegetables to the minimum needs.

The discovery that certain foods have biologically active compounds, beneficial to health beyond basic nutrition opened a new stage in nutrition science. These compounds or their metabolites that have been denominated "functional", help to prevent diseases like cancer, have a protective effect on cardiovascular problems, are neutralizers of free radicals, reduce cholesterol and hypertension, prevent thrombosis, besides other beneficial effects. Those foods that contain them are also called "functional" although other names such as "pharmafoods", "nutraceuticals", and others have been proposed. As most of these compounds are of plant origin, many authors call them phytochemicals. Fruits and vegetables are rich in phytochemicals like terpenes (carotenoids in yellow, orange and red fruits and limonoids in citrus), phenols (blue, red and purple colours of cherries, grapes, eggplant, berries, apples and plums), lignans (broccoli), thiols (sulfur compounds present in garlic, onion, leek and other alliums, cabbages and other crucifers) and others.

Flavour

Flavour is the combination of the sensations perceived by the tongue (taste) and by the nose (aromas) (Wills, et al., 1981). Although those sensations can be perfectly separated one from the other, as the sensitive receptors are so close, simultaneously with the act of bringing near the mouth, of biting, chewing, and tasting, we are perceiving the aromas, particularly those that are liberated with the crushing of tissues. It is also possible, however, that certain external aspects (particularly ripeness) anticipate the flavor that should be expected when consuming the product. The human being has stored in his/her memory an enormous quantity of different tastes and aromas and, if it was eaten previously, is able to recognize them without seeing the product.

In fruits and vegetables, taste is usually expressed in terms of the combination of sweet and sour principles that are an indication of ripeness and eating quality. The content of soluble solids is a good estimate of total sugar content, and many fruits should have a minimum content of solids to be harvested. Organic acids (citric, malic, oxalic, tartaric) are the other important components of taste, particularly in their relationship with soluble solids. As the fruit ripens they tend to diminish and so the relationship with the soluble solids tends to increase. Titratable acidity is the form of expressing acidity. The soluble solids/titratable acidity relationship is a denominated ratio and it is essentially used in citrus where it is a function of the species and of the variety. Its value is 8 for mandarins, Navel oranges, and hybrids, 7 for other type of oranges, and 5.5 for grapefruits (Lacey, et al., 2000).

Astringency (sensation of loss of lubrication in the mouth) and bitter tastes are due to different compounds. They are not frequent and when they exist, usually diminish with ripening. In those cases in which they appear naturally and represent a disadvantage, they have been eliminated through breeding programmes.

There are specific compounds that characterize certain species or a group of them, for example, pungency in the peppers denominated "hot" is basically determined by the capsaicin content and other 4 structurally similar compounds. There are also cases in which enzymes and substrata responsible for the taste are compartmentalized in healthy tissues and they only get in contact by cutting, chewing or crushing. This is the case of pungency in garlic and onion and also of the taste of raw cucumber. Cooking these vegetables whole prevents these reactions and the resulting taste is different.

There is a correlation between dry matter content and organoleptic characteristics mainly used by the industry. In general, a higher content of solids means higher industrial yield and taste. This is particularly important in dehydrated products. In potato, a higher content of dry matter (measured as specific gravity) is associated to a better cooking quality. For the fresh market, however, dry matter content is not used as an indicator of the time of harvest and/or organoleptic quality, except in the case of avocado where there is a close correlation with the oil content. Depending on the variety considered, avocados with a dry matter content lower than 21-23% should not be marketed (McCarthy, 2000).

The aroma of fruits and vegetables is due to the human perception of numerous volatile substances. Refrigerated fruits and vegetables are less aromatic since volatile liberation diminishes with temperature. As well as in the case of taste, many aromas are liberated when tissues lose their integrity.

Appearance

Appearance is the first impression that the consumer receives and the most important component of the acceptance and eventually of the purchase decision. Different studies indicate that almost 40% of the consumers decide what to buy inside the supermarket. Shape is one of the subcomponents more easily perceived, although in general, it is not a decisive aspect of quality, except in case of deformations or morphological defects. In some cases, shape is a ripeness index and therefore an indication of flavor. This is the case of the "full cheek" in mango or the "finger" angularity in bananas.

In those species where the inflorescence is the marketable organ such as broccoli or cauliflower or those that form "heads" like lettuce, cabbage, endive, etc. the compactness is the most relevant feature. In general, it is not associated to their organoleptic characteristics but rather is an indicator of the degree of development at harvest, since open inflorescences indicate that they were picked too late while non-compact "heads" are the consequence of a premature harvest. To a certain extent, it is also an indicator of freshness since compactness decreases with dehydration.

Uniformity is a concept applied to all the components of quality (size, form, colour, ripeness, compactness, etc.). For the consumer it is a relevant feature that indicates that someone that knows the product has already selected and separated it into categories based on the official standards of quality. It is so important that making products uniform is the main activity in preparation for the market.

In many cases, internal or external defects do not affect product excellence, but the consumer rejects them since the absence of defects is one of the main components of appearance and therefore, of the primary decision to purchase. Different causes during growth (climate, irrigation, soil, variety, fertilization, etc.) can lead to morphological or physiological defects. Some examples of the first ones are "doubles" in cherry, root ramifications in carrots, "catface" tomatoes, "knobby" tubers and "hollow heart" in potatoes, etc. Tipburn on leafy vegetables and black heart in celery due to calcium deficiencies as well as the internal rots in various species due to boron deficiencies are examples of physiological defects. More serious are those physical or physiological defects that originate during or after preparation for the fresh market and that show up at retail or consumer's level. Within the first ones we have the mechanical damages, bruises or wounds that take place during the handling of the product and that are the entrance doors to most pathogens causing postharvest rots. Chilling injury, ethylene effects as well as sprouting and rooting, are physiological responses to inadequate storage conditions.

Freshness and ripeness are part of the appearance and they have components of their own. They are also indicative of the expected flavor and aroma when products are consumed. "Freshness" is the condition of being fresh or as close to harvest as possible. It is used in vegetables where harvest is the point of maximum organoleptic quality characterized by the greatest turgidity, colour, flavor, and crispness. "Ripeness" is a concept used in fruits that also refers to the point of maximum eatable quality but that in many cases is reached at the level of sales point or of consumption since, in most commercial operations, fruits are harvested slightly immature. For example, fruits stored in controlled atmospheres reach their eatable quality after leaving the store room, several months after harvest.

Within the parameters for defining freshness and ripeness, colour, both intensity and uniformity, is the external aspect more easily evaluated by the consumer. It is decisive in those products like leafy vegetables or unripe fruits such as cucumber, snapbeans, and others where an intense green is associated with freshness and pale green one or yellowing to senescence. Colour is also an indicator of fruit ripeness and very important in those where no substantial changes take place after harvest (non-climacteric fruits), such as citrus, pepper, eggplant, and cucurbits in general. In fruits that suffer changes after harvest (climacteric) colour is less decisive and basically indicates the degree of ripeness, as for example tomato, pear, banana, etc.

Consumers assign to size a certain importance (Figure 63) and at equivalent quality, intermediate sizes are preferred. In fruits that are naturally large such as pumpkins, watermelons, melons, etc., there is a very defined trend towards sizes that can be consumed by a family (1-2 kg) in a relatively short period (1 week). Size is one of the main indicators of the moment of harvest and in many cases it is directly associated to other aspects of quality such as flavor or texture. Such is the case of zucchinis, peas, haricot beans and miniature vegetables in general where consumers particularly value small sizes.

Gloss enhances the colour of most products, but it is particularly valued in species like apple, pepper, eggplant, tomato, grapes, plums, cherries, etc., to such a point that many of them are waxed and polished to improve their shine. In vegetables, gloss is associated in a certain way to turgidity: a brilliant green is one of the indicators of freshness. It can also be used as a harvest index in eggplants, cucumbers, squash and other fruits that are harvested unripe where the decrease in shine indicates that they have developed too much and have lost part of their characteristics of flavour and texture. On the contrary, in melon, avocado, and other species, it is indicative that it has reached ripeness for harvest.

Different sensations perceived by humans are included within the definition of texture. Thus, firmness is perceived with the hands and, together with the lips, the kind of food surface (hairy, waxy, smooth, rough, etc.), while teeth determine the rigidity of the structure that has been chewed. The tongue and the rest of the mouth cavity detect the type of particles that are crushed by teeth (soft, creamy, dry, juicy, etc.). Also the ears contribute to the sensation of texture, for example, the noises generated when chewing in those species where crispness is an important aspect (Wills, et al., 1981).

Together with flavor and aroma, texture constitutes the eating quality. An over-ripe tomato, for example, is mainly rejected by its softening and not because important changes in the flavor or aroma have taken place. Although it is decisive for the quality of some fruits and vegetables, in others it has a relative importance. In texture terms, each product is valued differently: either for its firmness (tomato, pepper), the absence of fibers (asparagus, globe artichoke), its softness (banana), juiciness (plums, pears, citrus), crispness (celery, carrot, apple), etc.

Firmness and colour are the main parameters to estimate the degree of ripeness of a fruit since this process initially improves and softens fruit texture, which together with the changes in flavour and colour, bring the fruit to reach its maximum eatable quality. However, as this process continues, over-ripeness takes place, which leads finally to tissue disorganization and decay of the product. Firmness is used mainly as a harvest index and it is measured with instruments that register the force necessary for a certain deformation or resistance to the penetration of a piston of known dimensions.

Juiciness is the sensation of liquid spilling inside the mouth as tissues are chewed. The juice content of many fruits increases as they ripen in the plant. It is regulated that the minimum content that citrus fruits should have, is: 30% for Navel oranges; 35% for grapefruit and the other oranges; 25% for lemons; 33% for mandarins and 40% for clementines (Thompson, 1996).

Perception of quality

Quality is a complex perception of many attributes that are simultaneously evaluated by the consumer either objective or subjectively. The brain processes the information received by sight, smell, and touch and instantly compares or associates it with past experiences or with textures, aromas, and flavours stored in its memory. For example, just by looking at the colour, the consumer knows that a fruit is unripe and that it does not have good flavor, texture or aroma. If colour is not enough to evaluate ripeness, he/she uses the hands to judge firmness or other perceptible characteristics. The aroma is a less used parameter except in those cases where it is directly associated to ripeness like in melon or pineapple. This comparative process does not take place when the consumer faces, for the first time, an exotic fruit whose characteristics are unknown.

The final evaluation is the perception of the flavor, aroma, and texture that takes place when the product is consumed and when sensations perceived at the moment of purchase are confirmed. If satisfaction is the result, loyalty is generated. For example, if you discover that I prefer red apples to green ones, I will continue consuming red apples. It is possible to generate loyalty to commercial brands, presentation forms, packaging, sales places, etc.

Fruits and vegetables are consumed mainly for their nutritive value as well as by the variety of shapes, colours, and flavors that make them attractive for food preparation. When they are consumed raw or with very little preparation, the consumer's main concern is that they must be free of biotic or non-biotic contaminants that may affect health.

Definition of quality

The word "quality" comes from the Latin qualitas that means attribute, property or basic nature of an object. However, nowadays it can be defined as the "degree of excellence or superiority" (Kader, et al., 1985). Accepting this definition, we can say that a product is of better quality when it is superior in one or several attributes that are objectively or subjectively valued.

In terms of the service or satisfaction that it produces to consumers, we could also define it as the "degree of fulfillment of a number of conditions that determine its acceptance by the consumer". Here, a subjective aspect is introduced, since different consumers will judge the same product according to their personal preferences.

The destination or use can also determine different criteria for judging quality within the same crop. For example, the tomato for fresh consumption is valued essentially by its uniformity, ripeness, and absence of defects, while colour, viscosity, and industrial yield as raw material define the quality for ketchup tomatoes. It is common to use additional words to define the quality to the specific use, such as "industrial quality", "nutritional quality", "export quality", "edible quality", etc.

The papers here attached may assist in answering the question. Please have a look.

Quality can be judged by:

1 Textures

2 color

3 size

4 taste