Evaluation of simple and inexpensive high-throughput methods for phytic acid determination

Authors: Raboy, Victor; JOHNSON, AMY - American Oil Chemists' Society (AOCS); Bilyeu, Kristin; BRINCH-PEDERSEN, HENRICK - Danish Institute For Agricultural Science; Cichy, Karen; HURRELL, RICHARD - Swiss Federal Institute; ZEDER, CHRISTOPHE - Swiss Federal Institute Of Technology Zurich; RASMUSSEN, SOREN - University Of Copenhagen; WARKENTIN, TOM - University Of Saskatchewan; THAVARAJAH, PUSHPARAJAH - University Of Saskatchewan; SHI, JINRUI - Dupont Pioneer Hi-Bred; ZHOU, LAN - Dupont Pioneer Hi-Bred; SHU, QINGYAO - Zhejiang University

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2016
Publication Date: 1/9/2017
Citation: Raboy, V., Johnson, A., Bilyeu, K.D., Brinch-Pedersen, H., Cichy, K.A., Hurrell, R.F., Zeder, C., Rasmussen, S.K., Warkentin, T.D., Thavarajah, P., Shi, J., Zhou, L., Shu, Q. 2017. Evaluation of simple and inexpensive high-throughput methods for phytic acid determination. Journal of the American Oil Chemists' Society. 94(3):353-362. doi: 10.1007/s11746-016-2946-y?.

Interpretive Summary: Phytic acid is the major form of phosphorus in feed grains and legumes, accounting for approximately 70% of seed total phosphorus. As a result, phytic acid is a major form of phosphorus in feeds and foods. Feed and food phytic acid is not well digested by humans and non-ruminant animals such as chickens and pigs, and binds to nutritionally important minerals such as iron and zinc. Since phytic acid is not well digested by non-ruminants, much of the phosphorus in pig and chicken feeds ends up in waste, and this can contribute to water pollution. Also, consumption of phytic acid may lead to iron or zinc deficiency in humans. As a result of these issues and concerns, a method useful for testing for phytic acid in feeds and foods that meets the following criteria would be desirable: it must be accurate and reproducible whether the source of phytic acid is either a cereal grain or a legume such as soybean, and it must be inexpensive and widely accessible, using chemicals and equipment readily available to most labs. In this study an international group of scientists and laboratories cooperated in the evaluation of candidate methods that would fill those requirements. Methods were identified and described that are simple, inexpensive, accurate and reproducible for foods and feeds that contain either cereal grain or legume sources of phytic acid. These types of method will prove useful to crop breeders as well as those working in the food and feed industries.

Technical Abstract: High-throughput/low-cost/low-tech methods for phytic acid determination that are sufficiently accurate and reproducible would be of value in plant genetics, crop breeding and in the food and feed industries. Variants of two candidate methods, those described by Vaintraub and Lapteva (Anal. Biochem. 175:227-24, 1988; ”VL” methods) and Huang and Lantzsch (J. Sci. food Agric. 34:1423-1426, 1983; “HL” methods), were evaluated. The primary concern with these methods is that, due to interference of matrix constituents including inorganic P, they in some cases may overestimate and in other cases underestimate phytic acid and are ineffective at accurately measuring phytic acid when found at low levels in samples. Twelve seed flours, representing lines of soybean, maize, barley and dry bean, containing a wide range of phytic acid levels, were analyzed by eight cooperating laboratories using three variants of the VL method and two variants of the HL method. Some variants of the VL method were adequate for analyses of cereal grains regardless of phytic acid level but none accurately measured phytic acid when at low levels in soybean flours. One variant of the HL method in which the 0.2 N HCl extraction media is modified to contain 10% Na2SO4, did accurately measure phytic acid levels in both cereal and legume flowers regardless of endogenous phytic acid levels or matrix constituents.