Effect of Mild-Heat and High-Pressure Processing on Banana Pectin Methylesterase:  A Kinetic Study

Evidence on mechanism of instantaneous pressure softening of asparagus lettuce under high pressure processing was explored with respect to pectin methylesterase activity, degree of methylation of pectin, degree of methylation patterns of pectin fractions, and pectin distribution in cell wall matrix. Instantaneous pressure softening was observed at 300 MPa, while texture recovery was obtained at 500 MPa. Pectin methylesterase activity was not significantly affected at 100 and 300 MPa, but dramatically activated at 500 MPa (p < 0.05). Correspondingly, the degree of methylation of pectin decreased as pressure rose. Results of in situ immuno-dot blotting and immunolabeling based on specific bindings of antipectin antibodies showed a significant reduction of chelator-soluble pectin at 300 MPa, in contrast to a remarkable increase at 500 MPa. High pressure processing-induced demethoxylation was further verified by the enhanced fluorescence intensity of LM19 (an antihomogalacturonan antibody specifically binds to nonmethoxylated pectin) immunolabeled pectin, which was mainly located in tricellular junctions at 300 MPa, but covered the full cell surface at 500 MPa. In conclusion, instantaneous pressure softening of asparagus lettuce is strongly associated with loss of chelator-soluble pectin at 300 MPa.

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Impact of Alternative Thermal and Non-Thermal Processing on the Enzymatic Activity of Papaya and Strawberry Nectars and Their Blends

Journal of Food Engineering and Technology ◽

10.32732/jfet.2020.9.1.1 ◽

2020 ◽

Vol 9 (1) ◽

pp. 1-14

Author(s):

Jeffrey G. Swada ◽

Jose I. Reyes De Corcuera ◽

Nicki J. Engeseth

Keyword(s):

High Pressure ◽

Enzyme Activity ◽

High Temperature ◽

Thermal Processing ◽

Pectin Methylesterase ◽

High Pressure Processing ◽

Nutrient Loss ◽

Gel Formation ◽

Alternative Processing ◽

Processing Techniques

Pectin methylesterase (PME) in papaya nectar results in undesirable gel formation and peroxidase (POD) in strawberry nectar leads to nutrient loss, browning, and off-flavor production. Because of this, the effect of alternative processing techniques including ultra high temperature (UHT, 20-135°C, 1-3 s), high pressure processing (HPP, 20 or 60°C, 200-600 MPa) and irradiation (0-10 kGy) on PME and POD activity in papaya and strawberry nectar and their respective blends were compared to traditional thermal processing (80-130°C, 0-10 min). Traditional thermal (110°C, 5 min, 71.5% reduction) and UHT (110°C, 1-3 s, 98.0% reduction) processing were able to sufficiently reduce PME activity and prevent gel formation in papaya nectar. PME reduction was enhanced by synergistic reductions in nectar blends after UHT at 80°C. HPP was unable to prevent gel formation in papaya nectar, with enhanced activity at 400 MPa. Exposure of a blend 50P:50S to 10 kGy irradiation prevented gel formation. UHT enhanced POD activity at 110°C and synergistic reductions resulted for POD activity in nectar blends after irradiation. These findings highlight the benefits of alternative processing in reducing enzyme activity in fruit nectars and nectar blends.

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A Novel Method of a High Pressure Processing Pre-Treatment on the Juice Yield and Quality of Persimmon

Foods ◽

10.3390/foods10123069 ◽

2021 ◽

Vol 10 (12) ◽

pp. 3069

Author(s):

Jiayue Xu ◽

Yilun Wang ◽

Xinyue Zhang ◽

Zhen Zhao ◽

Yao Yang ◽

...

Keyword(s):

High Pressure ◽

Color Change ◽

Pectin Methylesterase ◽

High Pressure Processing ◽

Diospyros Kaki ◽

Yield And Quality ◽

Juice Yield ◽

Processing Modes ◽

Microorganism Inactivation ◽

Pre Treatment

This study investigates the effects of a high pressure processing pre-treatment (pre-HPP) on the juice yield of persimmon (Diospyros kaki L.) pulp and the pre-HPP plus HPP or thermal processing (TP) on microorganism inactivation and quality changes of the persimmon juice. The “Gongcheng” persimmon was selected with the highest juice yield (48.9%), and the pre-HPP set at 300 MPa/8 min increased the juice yield by 60% through an increasing pectin methylesterase (PME) activity of 25.03% and by maintaining polygalacturonase (PG) activity. For different processing modes, namely, pre-HPP plus HPP at 550 Mpa/5 min and pre-HPP plus TP treatment at 95 °C/5 min, both of the guaranteed microorganisms in the juice were below 2.0 lg CFU/mL; however, the persimmon juice treated by the pre-HPP plus HPP had higher contents of total phenol and ascorbic acid which were 16.07 mg GAE/100 g and 17.92 mg/100 mL, respectively, a lower content of soluble tannin which was 55.64 μg/mL, better clarity which was 18.6% and less color change where the ΔE was only 2.68.

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