DEVELOPMENT OF IMMUNOENZYME ANALYTICAL SYSTEMS FOR CONTROL OF THE CONTENT OF MAIN NON-MEAT COMPOUNDS IN PROCESSED MEAT PRODUCTS

Methods have been developed to control the content of non-meat components (connective tissue of animals, eggs, soy) in processed meat products, based on enzyme immunoassay of biomarker proteins – collagen, ovalbumin, soybean trypsin inhibitor.

Development of Enzyme-Linked Immunoassay Systems for Monitoring the Content of the Main Non-Meat Additives in Meat Products

Abstract-Methods for control of the content of non-meat components (connective tissue of animals, eggs, soybeans) in meat products have been developed based on competitive enzyme immunoassay of biomarker proteins: collagen, ovalbumin, and soybean trypsin inhibitor. Polyclonal rabbit antibodies against the biomarkers were produced. Screening of the following analysis conditions was carried out using the most affine preparations: the duration of the stages, the concentrations of the reagents, the composition of the reaction medium to ensure the completeness and the minimum limits of detection of analytes. It was shown that the immunochemical stage can be transferred to the kinetic mode and reduced to 20 min, while the total analysis took only 1 h. The selected conditions synchronized detection stages and provided the same signal amplitudes from all three biomarkers. An additional advantage of the method is that the analysis can be carried out at room temperature. The detection limits for collagen, ovalbumin and soybean trypsin inhibitor in the final extracts were 0.025 μg/mL, 0.012 μg/mL, and 0.001 μg/mL, respectively. Approbation of the method showed the reliability of the conclusions about the composition of the tested meat products; the relative standard deviation in the analysis of the monitored biomarkers was 8-10%. Key words: enzyme-linked immunoassay, meat products, collagen, ovalbumin, soybean trypsin inhibitor The work was financially supported by the Russian Science Foundation (project no. 19-16-00108).

Uremic solutes of indoxyl sulfate and p-cresol enhance protease-activated receptor-2 expression in vitro and in vivo in keratinocytes

Objectives: Uremic pruritus is common in patients with chronic kidney disease (CKD). The retention of uremic solutes is thought to be associated with uremic pruritus. Meanwhile, activation of protease-activated receptor-2 (PAR-2) has been suggested to play an important role in pruritus. The present study was performed to investigate the effects of uremic solutes on the expression of PAR-2 in the skin. Methods: Indoxyl sulfate (IS), p-cresol (PC), and uremic sera from CKD patients were used to stimulate PAR-2 expression in normal human epidermal keratinocytes (NHEKs). Also, NHEKs were additionally pretreated with soybean trypsin inhibitor to evaluate its inhibitory effect on PAR-2 expression. Patterns of cutaneous PAR-2 expression were investigated in skin samples from five CKD patients and CKD mice. Results: In NHEKs, IS, PC, and sera from CKD patients significantly induced PAR-2 mRNA and protein expression. Soybean trypsin inhibitor significantly decreased PAR-2 mRNA and protein expression in NHEKs treated with IS, PC, and CKD sera. NHEKs treated with IS and PC exhibited significant increases in protease activity. Skin from both CKD patients and mice exhibited marked upregulation of PAR-2 expression compared to control skin. Conclusions: Results from the present study suggest that uremic solutes either directly or indirectly affect PAR-2 expression in the skin of CKD subjects, potentially playing an important role in the pathogenesis of uremic pruritus.

Immunoreactivity of Lupine and Soybean Allergens in Foods as Affected by Thermal Processing

Lupine and soybean are important technological aids for the food industry. However, they are also capable of inducing severe allergic reactions in food-sensitized/allergic individuals. In this context, this work intended to study the combined effects of thermal processing and food matrix on the immunoreactivity of lupine and soybean proteins used as ingredients in bakery and meat products, respectively. For this purpose, the effects of baking, mild oven cooking, and autoclaving on the protein profiles were evaluated, using model mixtures simulating the production of lupine-containing breads and soybean-containing cooked hams/sausages, by native- and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and immunoblotting using specific antibodies. The results showed that lupine gamma-conglutin immunoreactivity was slightly decreased in wheat flour mixtures compared to rice, but it was more pronounced in baked products. In meat mixtures, substantial protein fragmentation was noted after autoclaving, with decreased immunoreactivity of soybean trypsin inhibitor. The analysis of 22 commercial products enabled the identification of lupine gamma-conglutin in four bakery samples and soybean trypsin-inhibitor in five sausages, and further differentiated autoclaved from other milder thermally treated products. Generally, the immunoreactivity of target proteins was reduced by all the tested thermal treatments, though at a higher extent after autoclaving, being slightly altered by the food matrix.