Yi Zhao,Xiufang Bi,Chunlei Ni,Ruifeng Ying,Khizar Hayat,Meigui Huang
This research utilized a laser particle size distribution analyzer, stability analyzer, atomic force microscope, fluorescence spectrophotometer, and ultra – performance liquid chromatography - mass spectrometry instrument to compare the impacts of pasteurization (PAST), ultra - high temperature instantaneous (UHT) sterilization, and ultra - high pressure (UHP) sterilization on the structure and stability of yak milk fat globules (MFGs). The findings indicated that all three sterilization methods led to a reduction in the diameter of fat globules and damaged the edge structure of the milk fat globule membrane (MFGM). Nevertheless, the stability was enhanced through the reduction of Young's modulus and micropolarity of the MFGM, with UHT milk fat globules exhibiting the highest stability. Lipidomic analysis revealed a decrease in the phospholipid content in UHT milk and UHP milk, whereas the phospholipid content in PAST milk increased. Therefore, the yak milk system after UHT sterilization is the most stable. These data can contribute to the improvement of the quality of yak milk products and facilitate the further development and utilization of yak milk resources.
Introduction: Lactose intolerance affects 85%–95% of Chinese adults, creating substantial demand for low-lactose dairy products. This study aimed to develop a cost-effective β-galactosidase production process through solid-state fermentation (SSF) using agricultural byproducts.Methods: A high-yielding strain was isolated from Tibetan fermented yak milk and identified through morphological, biochemical, and 16S rDNA sequence analysis. Solid-state fermentation conditions were optimized using single-factor experiments and Box-Behnken response surface methodology. Enzymatic properties were characterized, and the enzyme was applied to milk lactose hydrolysis. Techno-economic and environmental impact analyses were conducted.Results: Lactobacillus plantarum LP-15 exhibited initial enzyme activity of 44.7 U/g. Optimal SSF conditions were determined as substrate ratio of wheat bran:soybean meal:whey powder (6:3:1), 37 °C, pH 6.5, and 55% moisture content, achieving enzyme activity of 186.3 U/g (4.17-fold improvement). The enzyme exhibited optimal activity at pH 6.5 and 42 °C, with Km of 2.8 mM and catalytic efficiency of 5.3 × 104 M−1s−1. Milk lactose was reduced by 81.9% within 4 h using 2.0 U/mL enzyme at 40 °C, meeting the low-lactose standard (≤0.1%). SSF reduced production costs by 35.7%, water usage by 94%, and CO2 emissions by 62.4% compared to liquid fermentation.Discussion: This study provides an economically viable and environmentally sustainable solution for low-lactose dairy production in China, establishing independent intellectual property rights while addressing nutritional needs of lactose-intolerant populations through circular utilization of agricultural by products.
Die Li,Yutong Cui,Na Luo,Zixuan Guo,Jiyong Li,Fuhai Min,Jiliang Zhang
Fermented milk is the daily products facing many challenges, including natural flavor, good texture, and more health. In this study, the Leuconostoc mesenteroides and Saccharomyces cerevisiae were employed as the auxiliary fermenters to solve the challenge. After the fermentation, both cow fermented milk and yak fermented milk showing comprehensive fruit flavors, and the GC-MS/MS demonstrated that the generation of 19 kinds of volatile compounds including ester, ketone, aldehyde, and acid are major contributor and mainly provide fruit, flowers, and coconut flavor. Such as isoamyl acetate and ethyl caprylate, increased by 164.20 ± 8.04 µg/kg and 115.53 ± 13.49 µg/kg in ME after the addition of auxiliary fermenters. Meanwhile, the concentration of off-volatile compounds decreased or degradation by the fermentation with auxiliary fermenters, such as 3-methyl-2-butenal (roasted flavor). At the same time, the fermented milk participated with the auxiliary fermenters improve the texture, especially in firmness increasement by 1.28% and 27.7% for ME and YE, respectively. The result of scanning electron microscope also proofed that protein network was thicker with smaller gaps and larger clusters fermented by auxiliary than that of the control. The milk fermented participated with auxiliary increase the water holding capacity by 73.33% and 98.47% for ME and YE, respectively. And the total acceptance than that of the control.
危险品化学品经营许可证（带存储）