In vitro assay for protein digestibility: interlaboratory study

Area of Science:

• Nutritional Science
• Biochemistry
• Food Science

Background:

• Accurate estimation of protein digestibility is crucial for nutritional assessment and food formulation.
• Existing in vitro methods vary in enzyme systems and conditions, leading to discrepancies in results.
• A standardized, reproducible in vitro method is needed to reliably assess true protein digestibility across diverse food sources.

Purpose of the Study:

• To estimate the true protein digestibility of 17 diverse protein sources using a standardized in vitro three-enzyme digestion system.
• To evaluate the repeatability and reproducibility of this in vitro method across multiple laboratories.
• To establish a reliable method for assessing protein quality in animal, vegetable, and mixed food products.

Main Methods:

• An in vitro three-enzyme digestion system (trypsin, chymotrypsin, peptidase) was employed in a pH-stat setup.
• Six independent laboratories participated, using freeze-dried, ground samples of 17 protein sources and a sodium caseinate standard.
• Protein digestibility was calculated based on the uptake of titrant during enzymatic digestion.

Main Results:

• True protein digestibilities ranged from 100% for casein to 89.9% for whole wheat cereal.
• The in vitro method demonstrated high repeatability, with mean relative standard deviations of 1.4% for rolled oats and <1% for other samples.
• Reproducibility was also good, with relative standard deviations <2.5% for 13 out of 17 samples.

Conclusions:

• The standardized in vitro three-enzyme digestion system provides reliable and reproducible estimates of true protein digestibility.
• This method is suitable for assessing protein quality across a wide range of food sources.
• The findings support the use of this in vitro approach for nutritional research and food industry applications.