In this study, jujube polysaccharides were prepared by four different methods: hot water extraction, freeze-thaw pretreatment (–20 ℃) combined with rotary evaporation concentration (FR), freeze-thaw pretreatment (–20 ℃) combined with freeze concentration (FF), and cryogenic thermostatic reaction bath (–20 ℃) coupled with freeze concentration (CF). Our aim was to systematically explore the effect of low-temperature pretreatment combined with freeze concentration on the extraction efficiency, structural characteristics and in vitro hypoglycemic activity of jujube polysaccharides. Results revealed that cryogenic pretreatment significantly enhanced the hydroxyl (–OH) group content in polysaccharides and better maintained the triple-helix structure compared with traditional hot water extraction. Notably, FF was significantly advantageous in terms of polysaccharide yield, purity and in vitro hypoglycemic efficacy, increasing polysaccharide yield by 105.76%, elevating total sugar content by 25.29%, and reducing half maximal inhibitory concentration (IC₅₀) values for α-glucosidase and α-amylase by 80.1% and 73.4%, respectively compared with traditional hot water extraction. This study provides a new approach for the efficient low-temperature preparation of jujube polysaccharides and offers a theoretical basis for the development and application of natural hypoglycemic products.

The changes in the glass transition temperature (T_g), color, antioxidant components and antioxidant properties of a mixed freeze-dried powder of blueberry and blue honeysuckle berries were studied during at different temperatures (4, 25 and 37 ℃) and relative humidities (H_r, 43%, 75% and 95%) for up to 12 weeks. The behavior characteristics of the powder during storage were measured and analyzed as well. The results showed that compared with the other storage conditions, the basic physicochemical properties were better after 12 weeks of storage at 25 ℃ and 43% H_r (the T_g decreased by 4.62 ℃) or 4 ℃ and 75% H_r (the moisture content increased by 4.2%). In terms of the effect of antioxidant substance content and antioxidant capacity, with the prolongation of storage time, the contents of total phenols and total flavonoids and antioxidant capacity of different treatment groups decreased. The individual and total contents of six anthocyanins were least reduced at 25 ℃ and 43% H_r (the total anthocyanin content decreased by 23.92%), and the retention rate of total anthocyanins was higher at 4 ℃ and 75% H_r. The fluidity of the powder was maintained well after 12 weeks of storage at 25 ℃ and 43% H_r or 4 ℃ and 75% H_r. Therefore, both conditions were favorable for powder storage.

In order to explore the differences in the aroma quality of different white-fleshed peach cultivars, an electronic nose and headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to analyze the volatile components of eight cultivars of white-fleshed peach including Baiyintao (BYT), Longmi 5 (LM5H), Xinchuanzhongdao (XCZD), Qiutong (QT), Xindajiubao (XDJB), Yihongmi (YHM), Yihongshuimi (YHSM) and Okayama (GSB). Relative odor activity value (ROAV) and variable importance in projection (VIP) were used to analyze the contribution of each volatile component to the overall aroma of white-fleshed peaches. In the electronic nose radar fingerprint, the W1W, W5S, W1S and W2W sensors showed different responses to the eight cultivars. Principal component analysis (PCA) demonstrated differences in the overall aroma of white-fleshed peach cultivars. In total, 49, 46, 46, 47, 49, 47, 47, 53 volatile compounds were identified in BYT, LM5H, XCZD, QT, XDJB, YHM, YHSM, and GSB by HS-SPME-GC-MS, respectively, the major ones being aldehydes, alcohols, lactones and esters. 2-Hexenal, hexanal, trans-2-hexenal and trans-2-hexen-1-ol, contributing to grass aroma; linalool, contributing to floral aroma; and n-hexanol, responsible for fruity aroma, were identified as key aroma compounds due to their ROAV ≥ 1 and VIP > 1. Variations in their concentrations caused differences in the key aroma of the eight white-fleshed peach cultivars.