Many factors may affect starch composition in storage, depending on the type of storage and type of food/feed of interest. Furthermore, the digestibility of starch may change during storage. For example, the digestibility of starch in maize silage changes over the first 4 to 6 months of storage. Using fermentation as a storage method may change the amount of starch as well. Can you be more specific about your particular interests.
Dear Prof. Britt,
Thank you very much for your valuable suggestion. My query is about quantitative prediction of starch based on variables like structural and non-structural carbohydrates, lignin, protein, lipids etc., by any means of equation, if any.
Regards
Mahesh
Dear Sir,
Thank you very much once again for your useful documents.
Regards
Mahesh
In general
The sum of constituents in a feed is 100. Therefore if you calculate in DM basis you should have:
Minerals (Ashes) + Fat + Protein + Starch + Sugars + "Fibre" = 100
So if you have all other constituents you can estimate (roughly) starch.
The problem is how you take "fibre" into account in this calculation =
- NDF can be a good choice, although underestimating total (soluble) fibre and therefore overestimating starch in the above calculation.
- crude fibre cannot be used in the calculation because it represents+/- cellulose, but not all the hemicelluloses and pectic compounds. If you calculate (100-Ash-protein-fat-crude fibre) you get what used to be called "NFE" (Nitrogen Free extractives) which sums starch + sugars + hemicelluloses. It is not very useful.
If you have only crude fibre available you can estimate NDF from feed tables by calculating an expectted ratio between the two.
In particular
In specific raw materials there can be a very good relationship between starch and other constituents. Eg. in some cereal by products.
Dear Dr Denis,
Thank you very much for your detailed explanations.
Regards:
M.S. Mahesh
Just as an illustration a attach a chart of predicted vs measured starch content in maize bran (Uganda). Prediction following the equation given above. You notice a bias (about 5%) due to the fact that NDF doesn't represent tatal fibre (some soluble fibre are not included in NDF). However the R² is good (>0.95).
On the same data you can estimate starch more simply (2 parameters) by:
Starch (%DM) = 75.68 - 3.29*ASH - 3.42*C Fibre (R²=0.86)
Another example on a worldwide database of rice bran (342 samples)
Starch (%DM) = 75.86 - 1.07*ASH - 1.65*C Fat - 1.03* C Fibre (R²=0.91)
So, depending on the parameters you know or have access to (ash, protein etc.) you can establish prediction equations for starch on a particular material.
Dear Sir,
These equations are very useful.
May I get pdf version/link so that these can be used for calculation and subsequently cited.
Thanking you and regards:
M.S. Mahesh
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