CONICET | Buscador de Institutos y Recursos Humanos

The lactic acid fermentation is frequently used in food industry in order to enhance the nutritional, functional and sensory characteristics of several matrices such as soybean flour. In previous studies, solid state fermentation (SSF) was applied to obtain a preliminary semi-solid soy product with enhanced characteristics, using soybean flour as substrate and Lactobacillus (L.) paracasei subsp. paracasei CRL 207 as starter culture. It was evidenced that this lactic bacteria was able to hydrolyze the soy protein, increase the aglycone isoflavones and produce pleasant aromatic characteristics in the optimized conditions of SSF. Besides, the antioxidant capacity of protein and isoflavones was demonstrated in the fermented soy paste. The application of correct conservation processes is important to ensure that the product obtained is maintained in time and reaches the consumer correctly. Because of that, the aim of the present work was to analyze the effects of several conservation processes on the protein, isoflavones and aroma compounds from fermented soy paste. These processes were: storage during 28 days at 4 °C, freeze-dry and drying processes by heat with conventional stove at 45, 70 and 105 °C up to complete drying of the sample. The concentration of protein, free aminoacids and phenolic compounds was determined in soy paste after theses processes. Also, using SDS-PAGE and TLC, the effect of conservation processes on protein and isoflavones profile was analyzed. The antioxidant activity was also evaluated in each sample, applying the free radical (DPPH, ABTS+) scavenging methodology. The King method was used to analyze qualitatively the presence of aroma compounds in each sample. The concentration of phenolic compounds was similar in all tested samples showing that neither process affected its concentration. The isoflavones profile was maintained all over the processes. Regarding protein and peptides of treated samples, only the heat process at 70 °C showed an increasing of protein hydrolysis with the concomitant increase of free aminoacids (p< 0,05) in contrast with the samples of fermented soy paste without any treatment. The antioxidant activity was evidenced in all samples, protein, free aminoacids and isoflavones without significant differences. The aroma compounds were detected in all samples, in less extent in the soy paste after freeze-dry process. In conclusion, any of these conservation processes could be apply to storage the soy paste fermented with L. paracasei without loss of active compounds, even using the drying process at 70 °C it possible to enhance the digestibility of the protein with potential release of antioxidant peptides, maintaining the aroma compounds and the isoflavones profile. Drying process could be use to obtain soy ingredients with interesting characteristics to be apply in food industry