Resumen:
Lactic acid fermentation (LAF) has been used since antiquity to conserve food including starchy food. The bioaccessibility of starch depends on the food microstructures. Therefore, the understanding of the physicochemical transformations of the starch suffered during LAF will allow to develop an adequate processing of the alimentary matrices. In this work, native corn starch (NCS) dispersions were inoculated with Lactobacillus bulgaricus (2×107 cells ml−1) and fermented for 24 h at 38 ºC. Physicochemical changes of starch granules during fermentation time were monitored by XRD, FTIR and DSC. The crystallinity content achieved a maximum value (39.72±1.02%) after 12 h of fermentation. In contrast, the absorbance ratio 1047/1022 from FTIR measurements increased as the fermentation advanced. Likewise, DSC analysis showed that the gelatinization enthalpy increased 60.0% after 12 h of fermentation, reflecting the production of ordered microstructures. Thus, it is suggested that LAF increased the resistant starch content in corn starch granules.
Descripción:
Lactic acid fermentation with L. bulgaricus induced large changes in the morphology of corn starch granules. The production of amylolytic enzymes as well as lactic acid produced fractures along the granule hilum, which led to disintegration of starch granules at long fermentation times. On the other hand, lactic acid fermentation increased crystallinity and double-helices structures, which led to increased susceptibility to acidic hydrolysis. In fact, thermal analysis results indicated than an improved internal organization of granule residues occurred. In general, the results showed that the fermentation time can be considered as a suitable parameter for modulating the physicochemical properties of corn starch granules. Additionally, it can be postulated that lactic acid fermentation of starchy food matrices has a positive effect on the acidic digestibility of starch granules, by improving the content of resistant starch fractions
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