A Comparison of the ISO and AACC Methods for Determining the Activity of Trypsin Inhibitors in Soybean Meal

Abstract

The international standard method for the determination of trypsin inhibitor activity (TIA) in soya products, ISO 14902, was compared with the American Association of Cereal Chemists’ standard AACC 22‐40.01 as modified by Hamerstrand in 1981 (AACC‐based method), using soybean meals as matrices. TIA, expressed as milligram of inhibited trypsin per gram of sample, was determined by both methods in each of 30 samples of soybean meal. TIA values according to ISO 14902 were significantly lower (P < 0.001) than those afforded by the AACC‐based method. This difference, which means that AACC‐based method and ISO 14902 TIA values are not directly comparable, is attributable to between methods differences, in decreasing order of influence: particle size (P < 0.01), trypsin inhibitor extraction method (P < 0.05), and trypsin substrate (P < 0.01). N‐benzoyl‐l‐arginine‐4‐nitroanilide hydrochloride, the ISO 14902 trypsin substrate, affords TIA values 6.4 % higher than the racemic mixture used by the AACC method, but it seems unlikely that in most contexts this advantage would outweigh the disadvantage of its greater cost.

Soybean Trypsin Inhibitor Assay: Further Improvement of the Standard Method Approved and Reapproved by American Oil Chemists’ Society and American Association of Cereal Chemists International

“…Thus, the ISO method can be time consuming and expensive. Recently, Sueiro et al () made a direct comparison of the ISO method with the AACCI/AOCS approved method for measuring 30 soy samples and found a significant discrepancy in TIA values measured using the two methods. They attributed it to the differences between the two methods with respect to the sample particle size, TI extraction procedure, and enantiomers of the synthetic substrate, but noticeably failed to point out one additional but important difference between the two methods: the order of mixing reagents.…”

Use of The Bromocresol Purple Index (BCPI) in Measuring The Efficiency of Soybean Heat Treatment

“…Decreased distinguishability and reduced precision of TIA determinations can make it di cult to qualify soybean products correctly, particularly those the quality of which might be sometimes reduced due to excessive heat treatment [12]. Analogous results were obtained in the course of studies on soybean seeds and soybean meal treated with different heating methods [13], and those on microwave-heated soybean seeds [47]. The results of studies carried out on soybean our samples obtained from Nigerian soybean varieties [57] may also be interpreted similarly.…”

“…So far, the most commonly used traditional methods of analysing soybean seeds and products, based on the activity of selected enzymes (urease activity -UA) or thermolabile antinutritional factors (trypsin inhibitor activity -TIA) [43][44][45][46], often supplemented by methods based on protein solubility [18,43,45,46], despite their labour intensity and time-consuming nature, as well as complicated analytical procedures and the necessity to use expensive, specialized laboratory equipment operated by highly quali ed personnel, are still widely used in practice, even though thus obtained results are sometimes inaccurate and di cult to interpret. It should be noted that the UA and TIA test methods have been well veri ed in soybean meal studies and the obtained results of these parameters in this type of products were su ciently correlated [47].…”

Trypsin Inhibitor and Urease Activity of Soybean Meal Products from Different Countries and Impact of Trypsin Inhibitor on Ileal Amino Acid Digestibility in Pig

“…Subtle differences in the procedure such as sample homogeneity and particle size, extraction temperature and time, types of substrates etc., could result in substantial difference of TI results as reported previously (Liu, 2019;Rackis et al, 1974;Sueiro et al, 2015). For example, higher TI was found in 0.15 mm particle vs. 0.5 mm particle, higher TI in 3 hours room temperature extraction vs. 15-24 hours 4 C extraction (Sueiro et al, 2015). These different procedures are probably the main cause of the high inter-laboratory variability.…”

“…Several methods are described in the literature but the most common methods are ISO 14902 (ISO 14902:2001(ISO 14902: , 2012, the American Association of Cereal Chemists' Standard AACC 22-40.01 (1999), and American Oil Chemists' Society (AOCS) Official Method Ba 12-75 (1997), which are based on the original procedure of Hamerstrand and coworkers (Hamerstrand et al, 1981). As concluded previously (Sueiro et al, 2015;Liu, 2019), it is very difficult to compare results of TI content in soy products among different methods and different laboratories. Substantial differences in the quantified amount of TI can result from small modifications to the procedure, such as particle size of ground soy products, sample homogeneity, trypsin (source and purity), substrates (DL-BAPA vs. L-BAPA), extraction method (time and temperature), and many more.…”