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Insoluble dietary fiber (IDF) was extracted from wheat bran using the enzymatic method. The effects of dosages of alkaline protease and α-amylase as well as the duration of enzymolysis on the degrees of hydrolysis of protein and starch were investigated. The extraction conditions of IDF were optimized. The structure and physicochemical properties of IDF from wheat bran were studied.At the alkaline protease and α-amylase dosages of 4 000 U/g and 140 U/g, respectively, and the duration of enzymolysis of 2 h for each enzyme, the purity of extracted wheat bran IDF was 82.56%. The structure of wheat bran IDF was characterized by scanning electron microscopy, X-ray diffractometry, and Fourier transform infrared spectroscopy. The particles of extracted wheat bran IDF had holes and cracks on the surface, their crystalline structure was a typical type I cellulose crystalline structure, and the main components of wheat bran IDF were cellulose, lignin, and hemicellulose. The obtained wheat bran IDF showed higher water holding capacity (3.82 g/g), swelling power (2.59 mL/g), and oil holding capacity (1.78 g/g) than wheat bran, suggesting its potential application in flour products, gelled foods, and meat products to improve the stability and sensory qualities of the products. In addition, the nitrite ion clearance ability of wheat bran IDF reached 95.63%, implying its applicability as a functional ingredient in foods for reducing the negative impacts of nitrites on human health. These results provide guidance for improving the added value of wheat bran and for the application of wheat bran IDF in high-quality healthy foods. [ABSTRACT FROM AUTHOR]

Gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) techniques were used to analyze the effects of thermal pasteurization (TP) and high hydrostatic pressure (HHP) on the volatiles in litchi juice and lactobacillus fermented litchi juice. From the results, 70 volatiles were identified by GC-IMS, including ketones, alcohols, esters, aldehyde, and terpenoids. The TP process resulted in a severe loss of ethyl propionate, methyl 2-methylpropanoate, benzyl alcohol, and 1-octene-3-alcohol in fresh litchi juice, whereas volatiles such as butyl propionate, trimethylpyrazine, 5-nonone and 2,5-dimethylthiophene were more abundant after fermentation. The volatiles in HHP pretreated juice were similar to those in fresh litchi juice, and compounds such as linalool, 2,6-dimethylpyrazine, cis-rose ether, and benzaldehyde were more abundant in its fermented juice; 51 volatiles were identified by GC-MS, mostly comprising terpenoids and alcohols. The TP process decreased the contents of terpenoids and alcohols in litchi juice by 37.05% and 31.61% respectively. Compared with the fresh juice, terpenoid and alcohol content in HHP litchi juice increased by 33.57% and 80.07% respectively. The total content of volatiles in TP and HHP fermented litchi juice increased by 46.93% and 46.19% respectively, compared with the pretreated juice. The content of volatiles in HHP fermented litchi juice was 2.11 times higher than that in the TP fermented juice, with a more pleasant aroma. The combination of the two technologies shows that HHP pretreatment can effectively improve the aroma quality of litchi juice and fermented litchi juice, providing a reference value for improving the quality of fermented litchi juice. [ABSTRACT FROM AUTHOR]