anshan Yu

Effect of ultra-high pressure homogenisation processing on phenolic compounds, antioxidant capacity and anti-glucosidase of mulberry juice

In this study, the effects of ultra-high pressure homogenisation (UHPH) processing at 200 MPa for 1-3 successive passes (inlet temperatures at 4°C) were compared with pasteurisation (95°C, 1 min) processing on phenolic compounds, antioxidant capacity (ORAC value) and anti-glucosidase of mulberry juice. Compared with thermal pasteurisation processing, the more reductions in the anthocyanins, phenolic acids (gallic, protocatechuic, caffeic and p-coumaric acids, and a unknown hydroxycinnamic acid) and quercetin aglycone contents, as well as ORAC value were observed during UHPH processing of mulberry juice, whereas all reductions above during UHPH processing could be inhibited by adding ascorbic acid to mulberry juice. Besides, no significant change (p>0.05) in the α-glucosidase inhibitory activity was observed during UHPH processing of mulberry juice, but showed a 14% reduction in mulberry juice processed by thermal pasteurisation.

Osmotic dehydration of blueberries pretreated with pulsed electric fields: Effects on dehydration kinetics, and microbiological and nutritional qualities

ABSTRACT Fresh blueberries were treated by pulsed electric fields (PEF) at 2 kV/cm before osmotic dehydration in 70% cane sugar syrup. The changes in water loss, solids gain, populations of native microorganisms, antioxidant activity, contents of anthocyanins, predominant phenolic acids and flavonols, and total phenolics in blueberries were investigated after PEF pretreatment and during osmotic dehydration at 40°C. Compared with non-PEF-pretreated blueberry samples, PEF pretreatment reduced the osmotic dehydration time of blueberry samples from 120 to 48 h at target moisture content (3.0 g/g initial dry matter). No significant differences (p > 0.05) in total phenolics, antioxidant activity, anthocyanins, and predominant phenolic acids and flavonols were observed between the PEF-pretreated and non-PEF-pretreated blueberry samples. The PEF-pretreated blueberry samples had lower microbial populations than those which were not subjected to PEF pretreatment. Regardless of pretreatment, decreases in anthocyanins, predominant phenolic acids and flavonols, total phenolics, and antioxidant activity in blueberries were observed during the osmotic dehydration process. The results demonstrate that PEF pretreatment significantly reduced the dehydration time and enhanced the microbiological quality of blueberries without affecting their nutritional quality.

Combined Effect of Dimethyl Dicarbonate (DMDC) and Nisin on Indigenous Microorganisms of Litchi Juice and its Microbial shelf life

The individual and combined influences of dimethyl dicarbonate (DMDC) and nisin (200 IU/mL) at mild heat on the inactivation of indigenous microorganisms in litchi juice, including bacteria, molds and yeasts (M&Y), were investigated. The fresh litchi juice with or without nisin were exposed to 250 mg/L DMDC at 30, 40, or 45 °C for 0.5, 1, 2, 3, 4, or 6 h. A complete inactivation of M&Y in the litchi juice with or without nisin was achieved as exposed to 250 mg/L DMDC at 30, 40, or 45 °C for 0.5 h. The bacteria, especially Bacillus sp. and Leuconstoc mesenteroides showed higher resistance than M&Y in the litchi juice. Bacillus sp. and Leuconstoc mesenteroides in the litchi juice was not completely inactivated by 250 mg/L DMDC at 30, 40, or 45 °C. However, nisin addition can enhanced the inactivation of these bacteria by DMDC, and nisin and DMDC also showed a synergistic effect on the inactivation of bacteria. M&Y and bacteria were not detected in the litchi juice added with 200 IU/mL nisin as exposed to 250 mg/L DMDC at 45 °C for 3 h. In addition, microbial shelf life of the litchi juice during storage at 4 °C also was evaluated as treated by 250 mg/L DMDC or combination with nisin at 45 °C for 3 h.

Effect of High Pressure Homogenization and Dimethyl Dicarbonate (DMDC) on Microbial and Physicochemical Qualities of Mulberry Juice.

In this study, the effect of high pressure homogenization (HPH) and dimethyl dicarbonate (DMDC) on microbial and nutrient qualities of mulberry juice was evaluated. Results showed that repeated HPH passes at 200 MPa or adding DMDC at 250 mg/L significantly inactivated the indigenous microorganisms in mulberry juice (P < 0.05), whereas some surviving microorganisms recovered to grow during storage of 4 °C. The combined treatment with 3 passes of HPH and 250 mg/L of DMDC (HPH-DMDC) decreased the population of surviving indigenous microorganisms to the level attained by heat treatment at 95 °C for 1 min (HT) with no significant increase (P > 0.05) in the population of microorganisms during subsequent storage at 4 °C. Moreover, no significant changes (P > 0.05) in the physical attributes, including pH, TSS ((o) Brix), L*, a*, and b* values were observed in the samples treated by the HPH-DMDC or by HT. Compared with HT, HPH-DMDC treatment resulted in a higher degree of retention in total phenolics, and α-glucosidase inhibitory activity, although the treatment led to higher losses in cyanidin 3-glucoside, cyanidin 3-rutinoside, and antioxidant capacity. Overall, HPH-DMDC treatment can be a useful alternative to conventional thermal pasteurization of mulberry juice, considering its ability to inactive, and inhibit indigenous microorganisms.

Biochemical degradation and physical migration of polyphenolic compounds in osmotic dehydrated blueberries with pulsed electric field and thermal pretreatments

Fresh blueberries were pretreated by pulsed electric fields (PEF) or thermal pretreatment and then were subject to osmotic dehydration. The changes in contents of anthocyanins, predominantly phenolic acids and flavonols, total phenolics, polyphenol oxidase (PPO) activity and antioxidant activity in the blueberry samples during pretreatment and osmotic dehydration were investigated. Biochemical degradation and physical migration of these nutritive compounds from fruits to osmotic solutions were observed during the pretreatments and osmotic dehydration. PEF pretreated samples had the least degradation loss but the most migration loss of these compounds compared to thermally pretreated and control samples. Higher rates of water loss and solid gain during osmotic dehydration were also obtained by PEF pretreatment, reducing the dehydration time from 130 to 48h. PEF pretreated and dehydrated fruits showed superior appearance to thermally pretreated and control samples. Therefore, PEF pretreatment is a preferred technology that balances nutritive quality, appearance, and dehydration rate.

Slight Fermentation with Lactobacillus fermentium Improves the Taste (Sugar:Acid Ratio) of Citrus (Citrus reticulata cv. chachiensis) Juice.

The aim of this study was to evaluate the hypothesis that fermentation with Lactobacillus fermentium, which can metabolize citric acid, could be applied in improving the taste (sugar:acid ratio) of citrus juice. During fermentation, the strain of L. fermentium can preferentially utilize citric acid of citrus (Citrus reticulata cv. Chachiensis) juice to support the growth without the consumption of sugar. After 6 h of fermentation with L. fermentium at 30 °C, the sugar:acid ratio of citrus juice increased to 22:1 from 12:1, which resulted in that the hedonic scores of sweetness, acidity and overall acceptability of fermented-pasteurized citrus juice were higher than the unfermented-pasteurized citrus juice. Compared with unfermented-pasteurized citrus juice, the ORAC value and total amino acid showed a reduction, and no significant change (P > 0.05) in the L*, a*, b*, total soluble phenolics and ascorbic acid (Vc) content in the fermented-pasteurized citrus juice was observed as compared with unfermented-pasteurized citrus juice. Hence, slight fermentation with L. fermentium can be used for improving the taste (sugar:acid ratio) of citrus juice with the well retaining of quality.

Effects of Dimethyl Dicarbonate (DMDC) on the Fermentation of Litchi Juice by Lactobacillus Casei as an Alternative of Heat Treatment

UNLABELLED This study investigated the effects of dimethyl dicarbonate (DMDC) on the fermentation of litchi juice by Lactobacillus casei as an alternative of heat treatment that may have undesirable effect on the juice. Quality attributes and products stability of both the fermented heat- and DMDC-treated litchi juice by L. casei were compared. It was found that residual indigenous microorganisms in both the heat- and DMDC-treated litchi juice cannot grow into dominant bacteria during further fermentation of litchi juice by L. casei. Compared with fermented heat-treated litchi juice, fermented DMDC-treated litchi juice showed a better color, flavor, and overall acceptance, and also retained more total phenolics and antioxidant capacity. The viability counts of L. casei in both the heat- and DMDC-treated litchi juice were more 8.0 lg CFU/mL after 4 wk of storage at 4 °C. Also, some quality attributes in both the fermented heat- and DMDC-treated litchi juices, including pH, total phenolics, ascorbic acid, antioxidant capacity, and so on, showed the tendency to slow decrease during storage at 4 °C, but the scores of overall acceptance showed no reduction after the storage of 4 wk at 4 °C. On the whole, the application of DMDC treatment could be an ideal alternative of heat treatment to ensure the microbial safety, consistent sensory, and nutritional quality of fermented litchi juice prior to fermentation. PRACTICAL APPLICATION The pasteurization treatment is often recommended prior to fermentation of fruit juice by probiotics, as it would lead to a rapid inactivation and inhibition of spoilage and pathogenic bacteria, and ensure the fermented products with consistent sensory and nutritional quality. Dimethyl dicarbonate (DMDC) is a powerful antimicrobial agent, which was approved for use as a microbial control agent in juice beverages by FDA. This study provides a scientific basis for the application of DMDC prior to fermentation of litchi juice.

Inactivation of Escherichia coli and Staphyloccocus aureus in litchi juice by dimethyl dicarbonate (DMDC) combined with nisin.

Inactivation of Gram-negative Escherichia coli and Gram-positive Staphyloccocus aureus in litchi juice by DMDC combined with nisin was individually investigated. A 1.66 log cycles reduction of E. coli and 2.03 log cycles reduction of S. aureus in litchi juice (pH 4.5) added without nisin was achieved as exposed to 150 mg/l DMDC at 30 °C for 1 h, and the inactivation rate of E. coli and S. aureus during initial 1 h was far greater than during the remaining 5 h. As exposed to 150 mg/l DMDC at 30 °C for 1 h, the inactivation of E. coli and S. aureus in the litchi juice showed a trend toward increase with increasing of nisin addition level in the range from 0 to 200 IU/ml. Moreover, DMDC and nisin exhibited a synergistic effect on the inactivation of E. coli and S. aureus in litchi juice, and the inactivation of E. coli and S. aureus in the litchi juice also depends on the temperature of litchi juice, pH value of litchi juice and DMDC concentration when treated with DMDC and nisin. In addition, E. coli showed higher resistance to nisin as comparing with S. aureus. After E. coli and S. aureus in the litchi juice of pH 4.0 were individually treated with 150 mg/l DMDC combined with 200 IU/ml nisin at 30 °C for 1 h, a complete inactivation of S. aureus (6.59 log cycles) was achieved, but only 3.52 log cycles reduction of E. coli was observed.

Persimmon vinegar polyphenols protect against hydrogen peroxide-induced cellular oxidative stress via Nrf2 signalling pathway

Since polyphenols are known to exhibit antioxidative properties, we prepared and characterized persimmon vinegar polyphenols (PVP) in this study. Furthermore, we investigated the protective effect of PVP on hydrogen peroxide (H2O2)-induced oxidative stress in HepG2 cells and its underlying mechanisms. Our results showed that flavon-3-ols were the predominant polyphenols in PVP. Pre-treatment with PVP significantly decreased (p < 0.05) H2O2-induced cell damage in a dose-dependent manner, accompanied by decrease in lactate dehydrogenase (LDH) leakage, aminotransferase activities, and ROS accumulation. Moreover, PVP upregulated the expression of antioxidative enzymes, such as heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1), and increased the levels of glutathione. Western blotting results showed that PVP induced the nuclear translocation of nuclear factor (erythroid-derived-2)-related factor 2 (Nrf2). Taken together, our results indicated that PVP effectively protected HepG2 cells against oxidative stress via activation of the Nrf2 antioxidative pathway.

The effect of litchi juice on exopolysaccharide production in milk fermented by Lactobacillus casei

In this paper, Lactobacillus casei growth, sugar utilisation, exopolysaccharides (EPSs) formation and EPSs characterisation during fermentation of milk with or without litchi juice were evaluated. During L. casei fermentation of litchi-milk samples, the EPSs content increased with the increase of litchi juice levels (0– 25%, v/v), and the both relationship appeared in S-type curve. The viscosity of fermented milk also significantly increased with the formation of EPSs, and which positively correlated with the EPSs content (R = 0.9782). The EPSs from the fermented litchi-milk samples was isolated for further structural characterisation. Monosaccharide and molecular weight analysis of purified EPSs sample proved that it contained no carbohydrate other than glucose, and its molecular weight was calibrated as 3.03 9 10 Da. FT-IR and NMR (H and C) spectroscopy analysis confirmed the synthesised EPSs sample was a-glucans (dextrans) with mainly a-(1?6) linkages. To the best of our knowledge, this is the first study to report that litchi juice can enhance the EPSs (dextrans, mainly a-(1?6) linkages) production in fermented milk.