Gelation behavior and mechanism of Nicandra physalodes (Linn.) Gaertn. seeds pectin induced by Glucono-delta-lactone.

In this study, the physicochemical properties of pectin from Nicandra physalodes (Linn.) Gaertn. seeds (NPGSP) were analysed firstly, and the rheological behavior, microstructure and gelation mechanism of NPGSP gels induced by Glucono-delta-lactone (GDL) were investigated. The hardness of NPGSP gels was increased from 26.27 g to 226.77 g when increasing GDL concentration from 0 % (pH = 4.0) to 1.35 % (pH = 3.0), and the thermal stability was improved. The peak around 1617 cm-1 was decreased as the adsorption peak of the free carboxyl groups was attenuated with addition of GDL. GDL increased the crystalline degree of NPGSP gels, and its microstructure exhibited more smaller spores. Molecular dynamics was performed on systems of pectin and gluconic acid (GDL hydrolysis product), indicating that inter-molecular hydrogen bonds and van der Waals forces were the main interactions to promote gels formation. Overall, NPGSP has the potential commercial value for developing as a thickener in food processing.

Characterization of the flavor, sensory quality and in vitro bioaccessibility in cloudy pomegranate juice treated by high pressure and thermal processing.

BACKGROUND: Recently, cloudy pomegranate juice (PJ) has become popular due to its rich phenolic and health-promoting effects. The aim of the present work was to evaluate the application of high hydrostatic pressure processing (HPP), pasteurization (PT) and high-temperature short-time sterilization (HTST) on physicochemical properties (color, flow behavior, turbidity, sugars, organic acids, aroma and sensory evaluation) and in vitro bioaccessibility of total phenolics content (TPC), total flavonoids content (TFC) and phenolics of cloudy PJ. RESULTS: Compared to HPP, thermal sterilization significantly increased the brightness (L*), redness (a*), total color difference (ΔE) and turbidity, and decreased the TPC and TFC. HPP maintained the volatile profile of cloudy PJ better, while thermal sterilization significantly changed the profile by decreasing alcohols 23.8-32.7% and increasing acids by 33.6%-182.8%. The bioaccessibility of flavonoids, phenolic acids and tannins in the control cloudy PJ after in vitro oral-gastric-intestinal digestion were 1.5%, 4.9%, and 9.0%, respectively, which were not significantly changed by different treatments. CONCLUSION: These results contributed to promoting the color quality and health benefits of cloudy PJ rich in phenolics by optimizing the processing conditions in the food industry. © 2022 Society of Chemical Industry.

Transcription profile analysis for biosynthesis of flavor volatiles of Tunisian soft-seed pomegranate arils.

Flavor is an important factor affecting the sensory of pomegranate and its products, which easily lose its freshness during processing and storage, but the biosynthesis of flavor-associated compounds is poorly understood until now. In this study, combining metabolome and transcriptome, flavor-associated attributes and volatile compounds of Tunisian pomegranate arils from 7 Chinese regions were studied. Depending on the different planting areas, there were significant differences in the content of sugars, organic acids and vitamin C. A total of 40 volatile compounds were characterized from all samples, of which 13 volatile compounds were common to all samples. There were 4 compounds showed higher contents in all samples, including 1-hexanol, (Z)-3-hexen-1-ol, α-terpineol, and 2,4-di-tert-butyl phenol. According to the Kyoto Encyclopedia of Genes and Genomes pathway analysis, 5 differential accumulated metabolites, including palmitic acid, octanoic acid, lauric acid, decanoic acid, and myristic acid, were significantly enriched in the fatty acid biosynthesis for all samples. Weighted gene co-expression network analysis revealed that 42 candidate flavor-associated differentially expressed genes and 9 transcription factors mainly located in 3 key modules. Hexanoic acid was an important metabolite, which was significantly correlated with 38 differentially expressed genes. Generally, complex regulatory networks were constructed in the study to identify structural genes and transcription factors which regulate the metabolism of volatile compounds in pomegranate. Our results provided new insights for understanding the difference in flavor biosynthesis and regulatory network of pomegranate arils.

Comparison of the Effects of High Pressure Processing, Pasteurization and High Temperature Short Time on the Physicochemical Attributes, Nutritional Quality, Aroma Profile and Sensory Characteristics of Passion Fruit Purée.

The study investigated the effects of high-pressure processing (HPP) (600 MPa/5 min), pasteurization (PT) (85 °C/30 s), and high-temperature short time (HTST) (110 °C/8.6 s) on physicochemical parameters (sugar, acid, pH, TSS), sensory-related attributes (color, aroma compounds), antioxidants (phenolics, vitamin C, carotenoids, antioxidant capacity), and sensory attributes of yellow passion fruit purée (PFP). Compared to the PT and HTST, HPP obtained the PFP with better color, sugar, and organic acid profiles. Although PT was equally effective preservation of antioxidants and antioxidant capacity of PFP compared to HPP, high temperature inevitable resulted in the greater degradation of the aroma profile. The amounts of esters, alcohols, and hydrocarbon in PFP were significantly increased by 11.3%, 21.3%, and 30.0% after HPP, respectively. All samples were evaluated by a panel comprising 30 panelists according to standard QDA (quantitative descriptive analysis) procedure, and the result showed that HPP-treated PFP was rated the highest overall intensity score with 7.06 for its sensory attributes, followed by control (6.96), HTST (6.17), and PT (6.16). Thus, HPP is a suitable alternative technology for achieving the good sensory quality of PFP without compromising their nutritional properties.

Analysis of coloration characteristics of Tunisian soft-seed pomegranate arils based on transcriptome and metabolome.

In this study, combining metabolome and transcriptome, color related attributes and phenolic compositions of Tunisian pomegranate arils from 7 Chinese regions at same developing stage were studied. The total anthocyanin (TAC), flavonoids, and percent polymeric color (PPC) were ranged at 8.93-28.41 mg/100 g arils, 37.55-69.72 mg/100 g arils, and 3.38-21.96%, respectively. In total, 51 phenolic compounds were characterized, most of which were markedly higher in reddish-purple pomegranate arils than those levels in reddish pomegranate arils. In contrast, the accumulation of tannins was significantly higher in reddish pomegranate arils. Among the 49 differentially expressed genes, 8 and 5 genes were matched to ß-glucosidase and peroxidase, respectively. Correlation analysis showed that PPC was negatively correlated with 10 phenolic metabolites and TAC, positively correlated with L*, polymeric color, and 1 gene (|r| > 0.7, p < 0.01). Our results provide new insights for understanding the difference in coloration of pomegranate arils.