Modulating pectin structure and enhancing texture of frozen yellow peaches: The impact of low-temperature blanching.

High-temperature blanching (HTB) is the primary process that causes texture softening in frozen yellow peaches. The implementation of low-temperature blanching reduced pectin methyl esterification, increased pectin cross-linking, and mitigated pectin depolymerization during the subsequent HTB, leading to the superior texture of frozen yellow peaches with enhanced water holding capacity, higher fracture stress, and initial modulus. However, adding 2 % calcium lactate (w/v) during low-temperature blanching did not further improve the texture of frozen yellow peaches. Instead, it softened the texture by reducing Na2CO3-soluble pectin (NSP) and increasing water-soluble pectin (WSP) content. This study provided a theoretical basis for applying low-temperature blanching to improve the texture of frozen yellow peaches.

Synergistic mechanism of steam blanching and freezing conditions on the texture of frozen yellow peaches based on macroscopic and microscopic properties.

Freezing and blanching are essential processing steps in the production of frozen yellow peaches, inevitably leading to texture softening of the fruit. In this study, the synergistic mechanism of stem blanching, freezing conditions (-20°C, -40°C, -80°C, and liquid nitrogen [-173°C]), and sample sizes (cubes, slices, and half peaches) on macroscopic properties of texture, cellular structure, and ice crystal size distribution of frozen yellow peaches were measured. Blanching enhanced the heat and mass transfer rates in the subsequent freezing process. For nonblanched samples, cell membrane integrity was lost at any freezing rate, causing a significant reduction in textural quality. Slow freezing further exacerbated the texture softening, while the ultra-rapid freezing caused structural rupture. For blanched samples, the half peaches softened the most. The water holding capacity and fracture stress were not significantly affected by changes in freezing rate, although the ice crystal size distribution was more susceptible to the freezing rate. Peach cubes that had undergone blanching and rapid freezing (-80°C) experienced 4% less drip loss than nonblanched samples. However, blanching softened yellow peaches more than any freezing conditions. The implementation of uniform and shorter duration blanching, along with rapid freezing, has been proven to be more effective in preserving the texture of frozen yellow peaches. Optimization of the blanching process may be more important than increasing the freezing rate to improve the textural quality of frozen yellow peaches.

Polyphenolic-Protein-Polysaccharide Complexes from Hovenia dulcis: Insights into Extraction Methods on Their Physicochemical Properties and In Vitro Bioactivities.

Seven extraction methods, including hot water extraction (HWE), pressurized water extraction (PWE), ultrasound-assisted extraction, microwave-assisted extraction, ultrasound-assisted enzymatic extraction, high-speed shearing homogenization extraction, and ultrasound-microwave-assisted extraction, were utilized to extract polyphenolic-protein-polysaccharide complexes (PPPs) from Hovenia dulcis. Next, their physicochemical properties and in vitro antioxidant activities, antiglycation effects, and inhibition activities on α-glucosidase and α-amylase were studied and compared. The findings from this study indicate that various extraction processes exhibit notable influences on the physicochemical properties and in vitro bioactivities of PPPs. Extraction yields, contents of polyphenolics and flavonoids, apparent viscosities, molecular weights, molar ratios of monosaccharide compositions, and ratios of amino acid compositions in PPPs varied in different extraction methods. Furthermore, 13 phenolic compounds in PPPs, including rutin, myricitrin, myricetin, quercetin, kaempferol, protocatechuic acid, gallocatechin, p-hydroxybenzoic acid, ampelopsin, quercetin-7,4'-diglucoside, dihydroquercetin, 5-methylmyricetin, and naringenin, were identified. The relatively strong in vitro antioxidant activities, antiglycation effects, and inhibition activities on α-glucosidase and α-amylase were determined in both PPP-W and PPP-P obtained by HWE and PWE, respectively. The high content of total polyphenolics may be one of the main contributors to their in vitro bioactivities. The findings have shown that the PWE method can be an appropriate method to prepare PPPs with strong bioactivities for application in the functional food industry.

Effects of drying methods on the physicochemical characteristics and bioactivities of polyphenolic-protein-polysaccharide conjugates from Hovenia dulcis.

Four drying methods, including freeze drying, hot air drying, vacuum drying, microwave drying at 400, 600, and 800 W, were applied to dry the peduncles of Hovenia dulcis. Then the effects of different drying methods on physicochemical characteristics and bioactivities of polyphenolic-protein-polysaccharides conjugates extracted from H. dulcis (PPPs) were investigated and compared. Results showed that different drying methods affected the physicochemical characteristics and bioactivities of PPPs. Noticeable variations in extraction yields, contents of total proteins, contents of total polyphenolics, contents of total flavonoids, contents of uronic acids, molecular weights, apparent viscosities, molar ratios of constituent monosaccharides, ratios of constituent amino acids, and degrees of esterification were observed in PPPs obtained by different drying methods. Besides, a total of 13 phenolic compounds in PPPs were identified by UPLC-ESI-QTOF-MS. In addition, PPPs, especially PPP-M6 and PPP-V dried by microwave drying at 600 W and vacuum drying, respectively, exhibited remarkable antioxidant activities, antiglycation activities, and inhibitory activities on α-amylase and α-glucosidase. Results suggested that the microwave drying and vacuum drying techniques could be appropriate drying methods before extraction of PPPs with high bioactivities for applications in the functional food and medicine industries.