Feed & Additive Magazine Issue 3 April 2021

ARTICLE 74 FEED & ADDITIVE MAGAZINE April 2021 free amino groups remaining and thus the availability of the lysine for protein synthesis. Optimum values are above 90% reactive: total lysine ratio. Table 1 shows a comparison summary of these soy- bean meal quality parameters KOH SOLUBILITY AND PDI MAY NOT BE SENSITIVE TOOLS TO DETECT OVER-PROCESSED SOYBEAN MEAL Batal et al. (2000) (4) checked the impact of feed- ing processed soybean meal on broiler performance. Although KOH and PDI decreased with autoclav- ing time as expected, broiler performance was not affected, suggesting these methods of screening soybean meal quality may not be reliable tools to predict the true impact of soybean meal quality on animal performance. The US soybean export council also stated that KOH protein solubility is not sensitive enough to gauge the level of heat processing that a soybean meal product has undergone (5), indicating that KOH sol- ubility only provides qualitative and not quantitative information about a degree of over-processing. It is for these reasons that AB Vista has selected reactive lysine and UA as soybean meal quality in- dicators, which are available for customers to use on Feed Quality Service, AB Vista´s web-based NIR prediction service. REACTIVE LYSINE AS A QUANTITATIVE TOOL TO DETECT OVER-COOKED SOYBEAN MEAL During the D-T process in soybean meal production, the carbonyl group of sugars (reducing sugars) can react with the amino group of lysine, creating a mixture of poorly characterised Maillard products. In addition, the lysine can also react with other nutrients such as fats, polyphenols, vitamins and other food additives, creat- ing unspecified compounds (Figure 3). The issue with this chemical reaction is that a part of lysine de- tected as total lysine in HPLC analysis are not bioavailable for lean tis- sue ananolism or for oth- er biological function, as the heat damaged lysine is excreted through urine even if they are digest- ed and absorbed in the small intestine. Table 1: A comparison summary of soybean meal quality parameters (3) Under processing Over processing Target values Comment TIA Very appropriate Not appropriate <2.5 or <5 mg/g Difficult Reactive:Total Lysine Not appropriate Very appropriate >90% Difficult UA Very appropriate Not appropriate <0.05 or <0.30 pH rise Most common KOH Low use Appropriate 78 - 84 % Most common PDI Appropriate Low use 40 - 45 % Simple method Figure 3: Formation of Maillard products and unspecified compounds during soybean meal toasting process. (6)