Fourier transform infrared and Raman spectroscopic study of the effect of the thermal treatment and extraction methods on the characteristics of ayocote bean starches.

Starches isolated from four ayocote bean varieties were modified by thermal treatment to determinate the effect of the treatment on the structural changes of ayocote bean starch. Scanning electron microscopy indicates that the starch granules have oval and round shapes, with heterogeneous sizes and fractures when the extraction method is used. The presence of new bands at 2850 and 1560 cm-1 in the FT-IR spectra showed that the thermal treatment of ayocote beans induced an interaction between the protein or lipid and the amylose or amylopectin, while the sharpest band at 3400 cm-1 indicated a dehydration process in the starch granule in addition to the presence of the band at 1260 cm-1, indicating the product of the retrogradation process. The thermal treatment reduced the crystallinity as well as short-range order. Raman spectroscopy revealed that acute changes occurred in the polysaccharide bonds after thermal treatment. This study showed that the thermal treatment affected the structural properties of ayocote bean starches, the interactions of the lipids and proteins with starch molecules and the retrogradation process of starch.

Enzyme activity and partial characterization of proteases obtained from Bromelia karatas fruit and compared with Bromelia pinguin proteases.

The enzymatic activity and partial characterization of proteases from Bromelia karatas fruits were evaluated and compared with Bromelia pinguin proteases. The specific activity increased twofold after partial purification in both proteases. Partially purified proteases from Bromelia karatas showed good specific activity at pH 6.0-8.0 and residual activity of 70-100% for 60 min at 37-60 °C, similar to Bromelia pinguin proteases. The K m value of proteases from Bromelia karatas was higher (253.32 µM) than that of Bromelia pinguin proteases (234.94 µM). The use of specific protease inhibitors indicated the presence of cysteine and serine proteases. Proteases with molecular weight of 66.2-97 and 21-31 kDa were detected. Bromelia karatas proteases registered 73% hydrolysis using a soy protein concentrate, similar to the enzyme activity of Bromelia pinguin proteases and commercial bromelain. These results demonstrate that Bromelia karatas proteases could be a potential alternative protease in the food industry.