Analyzing the effect of TCA on grain protein digestibility with a modified formula for accurate nutritional evaluation in cereals.

Regarding the method for determining the in vitro digestibility of grain protein, there are two operations in the literature, with and without the addition of trichloroacetic acid (TCA), and the background value deduction is not standardized. In order to verify the effect of adding TCA on the determination of in vitro digestibility of cereal proteins, a gastric-trypsin two-step digestion method was used to enzymatically hydrolyze four kinds of cereals: rice, corn, millet, and quinoa. TCA was added before filtering the enzymatic solution. Comparative study with and without TCA. The results show that not adding TCA to the above 4 kinds of cereal enzymatic hydrolysates before filtration will lead to higher measurement results, with the results being higher by 2.85%, 3.42%, 15.97% and 18.74% respectively; the 4 kinds of cereal enzymatic hydrolysates added with TCA but not Subtraction of the gastric-trypsin background resulted in lower determination results, with the results being lower by 3.39%, 2.92%, 2.15% and 1.78% respectively. Based on the results of this experiment, a modified formula for determining grain protein digestibility by TCA precipitation method was proposed, which can ensure the accuracy of the calculation results. When using the precipitation method to determine the in vitro digestibility of grain protein, it is appropriate to add TCA precipitant, but the blank control values of pepsin and trypsin must be correctly deducted during the calculation process.

Introduction to Protein Digestibility Variability

The determination of in vitro digestibility of grain protein is a critical area of study, offering insights into the nutritional value and bioavailability of proteins from various cereals. This evaluation is vital for both human nutrition and animal feed, enabling the formulation of diets that maximize the nutritional uptake and health benefits. However, discrepancies in the methodology, particularly regarding the use of trichloroacetic acid (TCA) and the standardization of background value deduction, have led to variations in reported digestibility values. This paper discusses a systematic study aimed at clarifying the impact of TCA addition on the in vitro digestibility measurements of cereal proteins, proposing a modified formula to enhance the accuracy of these determinations.

Methodology of the Comparative Digestibility Study

Utilizing a gastric-trypsin two-step digestion method, this study enzymatically hydrolyzed proteins from four types of cereals: rice, corn, millet, and quinoa. A significant aspect of the methodology was the comparative analysis conducted with and without the addition of TCA prior to the filtration of the enzymatic solution. The addition of TCA is a common practice intended to precipitate proteins, thus facilitating their separation and analysis. However, the lack of standardization in its application has raised questions regarding the consistency of digestibility measurements.

Impact of TCA on Digestibility Measurements

The indings reveal a marked difference in digestibility results based on the presence of TCA. Specifically, the omission of TCA from the enzymatic hydrolysates of the cereals led to inflated digestibility values, with increases of 2.85% for rice, 3.42% for corn, 15.97% for millet, and 18.74% for quinoa, respectively. Conversely, the inclusion of TCA, without adjusting for the background activity of pepsin and trypsin, resulted in lower digestibility figures by 3.39%, 2.92%, 2.15%, and 1.78% for the respective grains. These discrepancies underscore the significance of TCA in the digestion process and the necessity for careful calibration of the enzymatic background values.

Proposal of a Modified Digestibility Measurement Formula

Building on these observations, the study proposes a modified formula for the determination of grain protein digestibility using the TCA precipitation method. This formula accounts for the enzymatic background, ensuring that the presence of TCA contributes to the accuracy of the measurement rather than introducing variability. The proposed approach advocates for the addition of TCA to precipitate proteins before filtration, paired with the meticulous deduction of blank control values for pepsin and trypsin during the calculation process. This methodological refinement is expected to standardize protein digestibility measurements, providing more reliable data for nutritional analysis and dietary formulation.

Conclusions and Implications for Nutritional Analysis

In conclusion, the study not only highlights the crucial role of TCA in the accurate assessment of cereal protein digestibility but also offers a methodological improvement that addresses existing inconsistencies. By standardizing the use of TCA and the deduction of enzymatic background values, this research contributes to the refinement of in vitro protein digestibility measurement techniques. Such advancements are essential for enhancing our understanding of cereal protein nutrition and optimizing dietary recommendations for both human health and animal feed efficiency.

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Original research was done by Fu Rongxia, Liu Yanmei, Zhou Xueyong, Xiao Jianzhong

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