Molecular modulating of amylopectin's structure promoted the formation of starch-unsaturated fatty acids complexes with controlled digestibility and improved stability to oxidation.

In this study, waxy corn starch (WCS) was modified by amylosucrase and pullulanase, producing linear starch chains with elongated length that favored the complexation with unsaturated fatty acids (uFAs). Compared to native WCS, the amylosucrase-modified WCS with an average chain length of 47.8 was easier to form V-type complexes with oleic acid, while increasing the degree of unsaturation impeded the formation of V-type complexes. The pullulanase treatment hydrolyzed the branching points of amylosucrase-modified WCS and the linear starch chains could forme V-type complexes with oleic acid, linoleic acid, and linolenic acid, with V-type crystallinity decreasing from 38.2 % to 20.1 %. V-type complexes had a lower thermal stability than the B-type starch crystallites, and their peak melting temperature ranged from 67.2 to 79.0 °C. The content of resistant starch in the complexes was in the range of 21.8 %-40.9 % and the formation of V-type complexes decreased the susceptibility of uFAs to oxygen.

Impact of crystalline structure on the digestibility of amylopectin-based starch-lipid complexes.

In this study, chain-elongated waxy corn starch (mWCS) was complexed with lauric acid (LA) to produce starch-lipid complexes (mWCS@LA) with a mixture of B- and V-type crystalline structures. Results from in vitro digestion showed that mWCS@LA had higher digestibility than mWCS, and the logarithm of slope plots of mWCS@LA revealed a two-stage digestion pattern, with digestion rate of the first stage (k1 = 0.038 min-1) being much higher than that of the following stage (k2 = 0.0116 min-1). The complexation between the long branch chains of mWCS and LA formed amylopectin-based V-type crystallites that were rapidly hydrolyzed during the first stage. The digesta isolated from the second stage of digestion had a B-type crystallinity of 52.6 %, and starch chains with degree of polymerization of 24-28 mainly contributed to the formation of the B-type crystalline structure. The results from the present study reveal that the B-type crystallites were more resistant to amylolytic hydrolysis than the amylopectin-based V-type crystallites.

Effects of Five Different Lactic Acid Bacteria on Bioactive Components and Volatile Compounds of Oat.

In this research, oats were fermented with Lactobacillus plantarum, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus bulgaricus and Streptococcus thermophilus for 48 h at 37 °C. The purpose of this work was to compare the growth capacities of the five lactic acid bacteria (LAB) in the oat matrix and the effects of fermentation on the contents of the bioactive components of oat, such as ß-glucan, polyphenols, flavonoids and volatile compounds at different time (0, 4, 8, 12, 24, 36 and 48 h). After 48 h of fermentation, the number of living L. acidophilus in oat reached 7.05 × 109 cfu/mL, much higher than that of other strains. S. thermophilus retained the greatest ß-glucan content, and L. casei had increased total polyphenol and total flavonoid contents. The proportion of free and bound polyphenols and flavonoids in all samples was changed by microbial action, indicating that forms of polyphenols and flavonoids can be transformed during the fermentation process, and the changes varied with different strains. The samples with L. plantarum, L. acidophilus, and L. casei fermentation contained more alcohols, whereas those with S. thermophilus and L. bulgaricus fermentation had more aldehydes, which revealed that the composition of volatile components was related to strains. The results indicate that oat substrate is a good medium for LAB growth. This study provides a reference for the use of different strains to achieve different fermentation purposes and a theoretical basis for the further processing of oat and fermented oat beverages.