Effect of high-pressure/high-temperature processing on chemical pectin conversions in relation to fruit and vegetable texture

Effect of pasteurization processing and storage conditions on softening of acidified chili pepper: Pectin and it related enzymes

The softening of acidified chili peppers induced by processing and storage has become a major challenge for the food industry. This study aims to explore the impact of pasteurization techniques, thermal processing (TP), high-pressure processing (HPP), addition of sodium metabisulfite (SMS), and storage conditions (25 °C, 37 °C, and 42 °C for 30 days) on the texture-related properties of acidified chili pepper. The results showed that the textural properties of samples were destructed by TP (the hardness of samples decreased by 19.43 %) but were less affected by HPP and SMS. Compared with processing, storage temperature had a more dominant impact on texture and pectin characteristics. With increased storage temperature, water-solubilized pectin fraction content increased (increased by 160.99 %, 136.74 %, and 13.01 % in TP, HPP, and SMS-stored groups, respectively), but sodium carbonate-solubilized pectin fraction content decreased (decreased by 29.84 %, 26.81 %, and 8.60 % in TP-, HPP-, and SMS-stored groups, respectively), especially in TP-stored groups. Multivariate data analysis showed that softening was more closely related to pectin conversion induced by acid hydrolysis and pectinase depolymerization. This finding offers new perspectives for the production of acidified chili pepper.

High-pressure pasteurization of low-acid chilled ready-to-eat food

The working population growth have created greater consumer demand for ready-to-eat (RTE) foods. Pasteurization is one of the most common preservation methods for commercial production of low-acid RTE cold-chain products. Proper selection of a pasteurization method plays an important role not only in ensuring microbial safety but also in maintaining food quality during storage. Better retention of flavor, color, appearance, and nutritional value of RTE products is one of the reasons for the food industry to adopt novel technologies such as high-pressure processing (HPP) as a substitute or complementary technology for thermal pasteurization. HPP has been used industrially for the pasteurization of high-acid RTE products. Yet, this method is not commonly used for pasteurization of low-acid RTE food products, due primarily to the need of additional heating to thermally inactivate spores, coupled with relatively long treatment times resulting in high processing costs. Practical Application: Food companies would like to adopt novel technologies such as HPP instead of using conventional thermal processes, yet there is a lack of information on spoilage and the shelf-life of pasteurized low-acid RTE foods (by different novel pasteurization methods including HPP) in cold storage. This article provides an overview of the microbial concerns and related regulatory guidelines for the pasteurization of low-acid RTE foods and summarizes the effects of HPP in terms of microbiology (both pathogens and spoilage microorganisms), quality, and shelf-life on low-acid RTE foods. This review also includes the most recent research articles regarding a comparison between HPP pasteurization and thermal pasteurization treatments and the limitations of HPP for low-acid chilled RTE foods.

Inhibition effect of high hydrostatic pressure combined with epigallocatechin gallate treatments on pectin methylesterase in orange juice and model system

High hydrostatic pressure (HHP) is currently the most successful non-thermal processing technology for commercial applications, but with a drawback that it is difficult to effectively inactivate the pectin methylesterase (PME), which is critical to the stability of orange juice. In this study, the PME inhibition and mechanism by HHP (600 MPa/10 min) combined with epigallocatechin gallate (HHP-EGCG) treatment were investigated. Firstly, the HHP-EGCG treatment showed enhancement effect on PME inhibition in orange juice, and the samples maintained higher content of water soluble pectin and exhibited higher suspension stability than the HHP treated samples during 13 days of refrigerated storage. Secondly, after HHP-EGCG treatment, further synergistic effect was observed in the phosphate buffer system, and the greatest secondary structure transformation and fluorescence quenching of PME occurred. Finally, molecule docking suggested that EGCG could interact with the active sites of PME, and transmission electron microscope results revealed further aggregation of PME under HHP-EGCG treatment.

Effects of radiofrequency blanching on lipoxygenase inactivation, physicochemical properties of sweet corn (Zea mays L.), and its correlation with cell morphology

This study investigated the effects of radiofrequency (RF) and boiling-water (BW) blanching on lipoxygenase (LOX) activity, physicochemical properties, and changes in the cellular morphology of sweet corn kernels. First, a speed-adjustable device was introduced to rotate the sample for improving heating uniformity. Then, the maximum RF heating rate and uniform temperature distribution of samples were obtained under 160 mm electrode gap, 120 g sample weight, and 14 r/min rotating speed. With increased RF heating temperature ranging from 50 °C to 80 °C, the residual activity of LOX significantly decreased to 4.68%. Samples blanched by RF treatment maintained better color, texture, and nutrient content than those by BW when similar levels of enzyme inactivation were achieved. Micrographs also showed the cells were increasingly damaged with increased RF heating temperature, whereas the cells were damaged much more severely when treated with BW. Besides, microscopic destruction of cells also explains the changes in physicochemical properties.

Formation of a bioactive cyclopentenone and its adducts with amino acids in sterilized-fruits and - vegetables baby foods

The formation of the molecule 4,5-dihydroxy-2-cyclopenten-1-one (DHCP) from the thermal treatment of pectin-containing foods was investigated in small-scale laboratory preparation of sterilized vegetable puree (carrot, zucchini and tomato) and fruit puree (peach and mixture of pear and apple) and in commercial baby foods. DHCP attracts attention due to its cytotoxicity as well as potential antiviral and anti-inflammatory effects. However, its effects and the difficulty of its identification in food are mediated in part by the formation of Michael adducts of DHCP with amino acids. The results revealed that DHCP reacted efficiently with cysteine and glutathione, and to a lesser extent with histidine. Mass spectrometry analysis confirmed the formation of adducts of DHCP with amino acids in a model system, being in a real food system difficult to investigate. However, these formed adducts are of potential interest, although it is not known whether they are safe, bioactive or reversible.

Effect of heating methods on astringency recurrence, syneresis, and physical properties of persimmon paste

The soluble tannins in Japanese persimmon gives it an unpleasant astringent taste, which can be removed using certain conventional methods. However, these methods are not very efficient and lead to the recurrence of astringency upon heating. Thus, the use of persimmon in processed food is severely limited. Although the effects of heating time and temperature on astringency recurrence have been explored in detail, the effect of the heating method used has not yet been clarified. Considering this, we subjected an astringency-removed paste to various heat treatments, namely, stir frying, boiling, and pressurization, and examined their effect on astringency recurrence. Soluble tannin contents were also determined, and sensory evaluation was conducted. It was observed that stir frying, which is accompanied by moisture evaporation, is superior with respect to the suppression of astringency recurrence and the prevention of syneresis compared with the other two methods. Moreover, the bright orange color and the gummy texture obtained upon stir frying are favorable for commercial purposes. Therefore, it is expected that these findings will lead to the significant improvement of astringent persimmon processing.

Impacts of thermal and non-thermal processing on structure and functionality of pectin in fruit- and vegetable- based products: A review

Pectin, a major polysaccharide found in the cell walls of higher plants, plays major roles in determining the physical and nutritional properties of fruit- and vegetable-based products. An in-depth understanding of the effects of processing operations on pectin structure and functionality is critical for designing better products. This review, therefore, focuses on the progress made in understanding the effects of processing on pectin structure, further on pectin functionality, consequently on product properties. The effects of processing on pectin structure are highly dependent on the processing conditions. Targeted control of pectin structure by applying various processing operations could enhance textural, rheological, nutritional properties and cloud stability of products. While it seems that optimizing product quality in terms of physical properties is counteracted by optimizing the nutritional properties. Therefore, understanding plant component biosynthesis mechanisms and processing mechanisms could be a major challenge to balance among the quality indicators of processed products.

Marine Microalgae, Spirulina maxima-Derived Modified Pectin and Modified Pectin Nanoparticles Modulate the Gut Microbiota and Trigger Immune Responses in Mice

This study evaluated the modulation of gut microbiota, immune responses, and gut morphometry in C57BL/6 mice, upon oral administration of S. maxima-derived modified pectin (SmP, 7.5 mg/mL) and pectin nanoparticles (SmPNPs; 7.5 mg/mL). Metagenomics analysis was conducted using fecal samples, and mice duodenum and jejunum were used for analyzing the immune response and gut morphometry, respectively. The results of metagenomics analysis revealed that the abundance of Bacteroidetes in the gut increased in response to both modified SmP and SmPNPs (75%) as compared with that in the control group (66%), while that of Firmicutes decreased in (20%) as compared with that in the control group (30%). The mRNA levels of mucin, antimicrobial peptide, and antiviral and gut permeability-related genes in the duodenum were significantly (p < 0.05) upregulated (> 2-fold) upon modified SmP and SmPNPs feeding. Protein level of intestinal alkaline phosphatase was increased (1.9-fold) in the duodenum of modified SmPNPs feeding, evidenced by significantly increased goblet cell density (0.5 ± 0.03 cells/1000 µm2) and villi height (352 ± 10 µm). Our results suggest that both modified SmP and SmPNPs have the potential to modulate gut microbial community, enhance the expression of immune related genes, and improve gut morphology.

Understanding the influence of processing conditions on the extraction of rhamnogalacturonan-I "hairy" pectin from sugar beet pulp

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Conventional and microwave-assisted extraction of “hairy” pectin from sugar beet.

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Determined effect of heating method, temperature, time & pH on yield & composition.

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No difference between microwave and conventional extraction under conditions tested.

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Strong alkaline is favoured in rhamnogalacturonan-I “hairy” pectin extraction.

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Hydrothermal water extraction can be an alternative to strong alkaline extraction.

Sugar beet pectin is rich in rhamnogalacturonan-I (RG-I) region, which is a potential source of prebiotics. RG-I pectin cannot be extracted the same way as commercial homogalacturan-rich pectin using hot acid. Therefore, this study has explored several alternative methods, including microwave-assisted extraction (MAE) and conventional-solvent extraction (CSE) at atmospheric pressure using different solvents, and microwave-assisted hydrothermal extraction (MAHE) under pressure using water. No conclusive differences in microwave and conventional heating were found with heating rate controlled. The optimum treatment times of both MAE and CSE at 90 °C atmospheric pressure and regardless of the solvents used were 120 min; however, MAHE at 130 °C under pressure can dramatically reduce the time to 10 min. Alcohol-insoluble solids (AIS) extracted using pH13 solvent by MAE had both the highest RG-I yield at 25.3% and purity at 260.2 mg/g AIS, followed by AIS extracts using water by MAHE with 7.5% and 166.7 mg/g AIS respectively.

New evidence on pectin-related instantaneous pressure softening mechanism of asparagus lettuce under high pressure processing

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.

Viscoelastic properties of soy protein isolate - pectin blends: Richer than those of a simple composite material

Concentrated soy protein isolate (SPI) - pectin blends acquire fibrous textures by shear-induced structuring while heating. The objective of this study was to determine the viscoelastic properties of concentrated SPI-pectin blends under similar conditions as during shear-induced structuring, and after cooling. A closed cavity rheometer was used to measure these properties under these conditions. At 140 °C, SPI and pectin had both a lower G* than the blend of the two and also showed a different behavior in time. Hence, the viscoelastic properties of the blend are richer than those of a simple composite material with stable physical phase properties. In addition, the G'_pectin was much lower compared with the G'_SPI and G'_SPI-pectin upon cooling, confirming that pectin formed a weak dispersed phase. The results can be explained by considering that the viscoelastic properties of the blend are influenced by thermal degradation of the pectin phase. This degradation leads to: i) release of galacturonic acid, ii) lowering of the pH, and iii) water redistribution from the SPI towards the pectin phase. The relative importance of those effects are evaluated.

Pectin structure and particle size modify carotenoid bioaccessibility and uptake by Caco-2 cells in citrus juices vs. concentrates

Pectin changes from a citrus-based product modify bioaccessibility and carotenoid uptake by intestinal cells.

Changes in pectin characteristics during the ripening of jujube fruit

BACKGROUND

Pectin is related to fruit maturation and loss of flesh firmness. In this research, changes in pectin characteristics, including pectin content, neutral sugar composition, molecular weight (M_w ) distribution and degree of methylesterification (DM), in six different growth stages (S1 to S6) of jujube fruit were assessed.

RESULTS

The growth of jujube fruit corresponded to an increase in water-soluble pectin (WSP) and a decrease in sodium carbonate-soluble pectin (SSP). The chelate-soluble pectin (CSP) content reached a maximum level at S3 but decreased significantly from S3 to S4. Arabinose proved to be the principal branched neutral monosaccharide in pectin during growth and was lost from WSP, CSP and SSP in S4 to S6. The ratios of (arabinose + galactose)/rhamnose indicated that the branched chains of WSP, CSP and SSP degraded in S2, S3 and S4 respectively. SSP depolymerized from S2 and increased as jujube fruit ripened. By contrast, WSP depolymerized throughout ripening. The DM of pectins ranged from 45.38 to 92.21%. Among the obtained DMs, the lowest was observed in WSP from ripened jujube fruit (S6).

CONCLUSION

The content, neutral sugar composition, DM and M_w distribution of pectins changed markedly as jujube fruit ripened. Jujube fruit could be a promising alternative source of pectins in terms of maturation degree. WSP from S6 and CSP from S1 or S2 could be used as gelling agents in low-sugar-containing products because of their low methoxyl pectin contents. WSP from S1 could also be applied as a thickener or emulsifier owing to its high M_w distribution. © 2017 Society of Chemical Industry.

Innovative "Green" and Novel Strategies for the Extraction of Bioactive Added Value Compounds from Citrus Wastes-A Review

Citrus is a major processed crop that results in large quantities of wastes and by-products rich in various bioactive compounds such as pectins, water soluble and insoluble antioxidants and essential oils. While some of those wastes are currently valorised by various technologies (yet most are discarded or used for feed), effective, non-toxic and profitable extraction strategies could further significantly promote the valorisation and provide both increased profits and high quality bioactives. The present review will describe and summarize the latest works concerning novel and greener methods for valorisation of citrus by-products. The outcomes and effectiveness of those technologies such as microwaves, ultrasound, pulsed electric fields and high pressure is compared both to conventional valorisation technologies and between the novel technologies themselves in order to highlight the advantages and potential scalability of these so-called "enabling technologies". In many cases the reported novel technologies can enable a valorisation extraction process that is "greener" compared to the conventional technique due to a lower energy consumption and reduced utilization of toxic solvents.

Immunolocalization of pectic polysaccharides during abscission in pea seeds (Pisum sativum L.) and in abscission less def pea mutant seeds

BACKGROUND

In pea seeds (Pisum sativum L.), the presence of the Def locus determines abscission event between its funicle and the seed coat. Cell wall remodeling is a necessary condition for abscission of pea seed. The changes in cell wall components in wild type (WT) pea seed with Def loci showing seed abscission and in abscission less def mutant peas were studied to identify the factors determining abscission and non-abscission event.

METHODS

Changes in pectic polysaccharides components were investigated in WT and def mutant pea seeds using immunolabeling techniques. Pectic monoclonal antibodies (1 → 4)-β-D-galactan (LM5), (1 → 5)-α-L-arabinan(LM6), partially de-methyl esterified homogalacturonan (HG) (JIM5) and methyl esterified HG (JIM7) were used for this study.

RESULTS

Prior to abscission zone (AZ) development, galactan and arabinan reduced in the predestined AZ of the pea seed and disappeared during the abscission process. The AZ cells had partially de-methyl esterified HG while other areas had highly methyl esterified HG. A strong JIM5 labeling in the def mutant may be related to cell wall rigidity in the mature def mutants. In addition, the appearance of pectic epitopes in two F3 populations resulting from cross between WT and def mutant parents was studied. As a result, we identified that homozygous dominant lines (Def/Def) showing abscission and homozygous recessive lines (def/def) showing non-abscission had similar immunolabeling pattern to their parents. However, the heterogeneous lines (Def/def) showed various immunolabeling pattern and the segregation pattern of the Def locus.

CONCLUSIONS

Through the study of the complexity and variability of pectins in plant cell walls as well as understanding the segregation patterns of the Def locus using immunolabeling techniques, we conclude that cell wall remodeling occurs in the abscission process and de-methyl esterification may play a role in the non-abscission event in def mutant. Overall, this study contributes new insights into understanding the structural and architectural organization of the cell walls during abscission.

Effects of ultraviolet light (UV-C) and heat treatment on the quality of fresh-cut Chokanan mango and Josephine pineapple

The effects of ultraviolet (UV-C) and medium heat (70 °C) treatments on the quality of fresh-cut Chokanan mango and Josephine pineapple were investigated. Quality attributes included physicochemical properties (pH, titratable acidity, and total soluble solids), ascorbic acid content (vitamin C), antioxidant activity, as well as microbial inactivation. Consumers' acceptance was also investigated through sensory evaluation of the attributes (appearance, texture, aroma and taste). Furthermore, shelf-life study of samples stored at 4 ± 1 °C was conducted for 15 d. The fresh-cut fruits were exposed to UV-C for 0, 15, 30, and 60 min while heat treatments were carried out at 70 °C for 0, 5, 10 and 20 min. Both UV-C and medium heat treatments resulted in no significant changes to the physicochemical attributes of both fruits. The ascorbic acid content of UV-C treated fruits was unaffected; however, medium heat treatment resulted in deterioration of ascorbic acids in both fruits. The antioxidants were enhanced with UV-C treatment which could prove invaluable to consumers. Heat treatments on the other hand resulted in decreased antioxidant activities. Microbial count in both fruits was significantly reduced by both treatments. The shelf life of the fresh-cut fruits were also successfully extended to a maximum of 15 d following treatments. As for consumers' acceptance, UV-C treated fruits were the most accepted as compared to their heat-treated counterparts. The results obtained through this study support the use of UV-C treatment for better retention of quality, effective microbial inactivation and enhancement of health promoting compounds for the benefit of consumers.

Application of high pressure processing for shelf life extension of litchi fruits (Litchi chinensis cv. Bombai) during refrigerated storage

This study attempts to report the effect of high pressure processing (100, 200 and 300 MPa for 5, 10 and 15 min at 27 ± 2 ℃) on quality and shelf life extension of 'Bombai' variety peeled litchi fruits during refrigerated storage (5 ℃). High pressure processing significantly increased total colour difference, browning index, drip loss and total soluble solids, whereas pH decreased after processing. Also, ascorbic acid content significantly decreased after high pressure processing and retention of 83.5% was observed. Texture profile analysis showed that pressurization significantly affected firmness and increased cohesiveness, gumminess, springiness and chewiness of litchi fruits. Pressure-induced firming effect was observed at 100 and 200 MPa pressure. A maximum of 3.29, 3.24 and 3.77 log10 cycles reduction in aerobic mesophiles, yeast & mold and psychrotrophs count, respectively, was achieved after pressurization of 300 MPa for 10 and 15 min treatments. During storage, samples treated at 300 MPa for 10 and 15 min showed relatively minimal changes in physico-chemical attributes, textural parameters and maintained lower viable microbial counts. Treatments at 300 MPa for 10 min and 15 min were found to enhance the shelf life of litchi fruits up to 32 days as compared to 12 days of untreated during refrigerated storage (5 ℃).