I am looking for standard digestibility protocol. At some places single enzyme digestibion is done like pepsin digestion at other trypsin...and in some cases in vitro gastric digestion using simulated gastric fluid. Are there any guidelines / standard protocol to check digestibility of cereal products???
Kindly help!! Thanks
Hello Niharika Sachdev ,
There are improved digestibility protocols for both proteins and starches. I guess you are specifically talking about proteins because you mentioned proteases (pepsin, trypsin). There is a method developed by Mertz et al.,1984 and improved by Aboubacar et al., 2001, specifically used for sorghum kafirins, although it is not quit reliable. Both papers are attached.
Yes, I saw these papers. I tried doing the test as per these protocols. But I have also seen that the same protocol is applied on conc protein..I mean sample size taken for test is 200mg whether it is flour or isolate..also pepsin used by different researchers had different activities but conc used is again same 1.5mg/ml. But conc of pepsin in stomach is in the range 0.5-1mg/ml. So why higher concentration is used? At the end some doing just pepsin digestion some with trypsin some simulated in vitro models. So what protocol is followed while developing product at commercial scale.
Niharika Sachdev You raised a good point for discussion. From what I understand, none of the methods are wrong or none are called "standard". People try to replicate what they believe happens in the upper GIT and try to compare the digestibility of proteins for different grains with different treatments or protein isolates, ...etc. The results may not be questioned as the exact same condition and method are used for all in a set of an experiment.
Regarding the concentration of pepsin in the stomach and the ones used in the methods, I personally do not think it matters. If we think about it, there are huge differences for individuals and that also depends on the food habit. Similarly on the use same concentrations of enzymes for flour and protein isolates, I think it again doesn't matter because enzymes are catalysts, which means they do not get consumed in the process. They get recovered/regenerated for multiple catalytic roles. If we think about the real situation, humans consume food with some proteins or no proteins at times and food with high proteins (equivalent to protein isolates) at other times.
I hope this helps in the discussion. Thanks.
Hello, thanks for replying! It is true that results may not be questionable as exact same conditions are used. Also individual conditions do vary. But while experiments results are variable with the factors affecting digestibility. how can I call protein to be susceptible or resistant to digestion if the protocol selected by various researcher is on the basis of mode of their appearance in literature. I saw that pepsin conc vary from 0.5 to 1 mg/ml in human stomach. pH condition vary from 1.5 to 2.5 and incubation time varies from 1-4 hrs. so how to decide for one particular substrate protein this or that condition would be optima? and so the protein is susceptible or resistant to digestion? can we call the substrate protein indigestible based on assay done for 1 hr of gastric digestion and 2 hr of intestinal digestion? so now I saw some papers taking average activity of pepsin to be 10U for 1 microgram.
Article A new in vitro method to evaluate digestibility of commercia...
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