The protein dispersibility index in the quality control of heat-treated full-fat soybeans: an inter-laboratory study

Abstract

________________________________________________________________________________ AbstractThere are a number of laboratory methods that could be used to estimate the adequacy of full-fat soybean (FFSB) heat treatment. The protein despersibility index (PDI) has been claimed to have the most constant response to the heating of FFSBs. In this study, the PDI method has been subjected to an interlaboratory test, including the participation of eight laboratories. Seven FFSB samples were processed by dry extrusion at temperatures ranging from 110 to 164 °C and analysed on the PDI. Processed FFSB samples were also assessed in a growth trial of broilers. The analysis of the FFSBs by the PDI method generated adequately-processed FFSB values of between 8.49% and 10.3%. Values above 10.3% described underprocessed and below 8.49% over-processed FFSBs. The PDI method generated a good repeatability limit of 2.1%, but the reproducibility limit (7.73%) was too wide when taking into account the narrow range (8.5 -10.3%) for adequately heat-treated FFSBs. Despite its simplicity and initial indications that it might be the best indicator of FFSB heat treatment, the PDI method did not prove that in this inter-laboratory study.________________________________________________________________________________

Investigation into the physiochemical properties of soy protein isolate and concentrate powders from different manufacturers

“…Higher PDI values, especially those approaching 100%, indicate greater protein–water interactions and may be due to a milder treatment during the extraction and purification, and therefore, a low extent of protein denaturation and aggregation (Palić et al ., 2011; Lehmali & Jafari, 2019). In the context of meat analogue processing, a higher PDI indicates better dispersibility and a more uniform distribution of soy protein in the formulation, which allows consistent texture and structure in the final product.…”

“…In the context of meat analogue processing, a higher PDI indicates better dispersibility and a more uniform distribution of soy protein in the formulation, which allows consistent texture and structure in the final product. By contrast, lower PDI values indicate lower solubility in proteins and a higher degree of denaturation which enhances their tendency to aggregate/clump together (Palić et al ., 2011).…”

“…Accordingly, higher PDI values for all soy protein powders seem reasonable when compared to protein solubility values. It is, moreover, amplified by the different testing method used (Palić et al, 2011). The protein solubility method involves relatively mild mixing conditions (magnetic stirrer; 950 rpm for 60 min), while the PDI method involves high shear mixing (Ultraturrax ® ; 37 604 g for 10 min).…”