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Foodborne diseases are an important public health problem in the world. The bacterial resistance against presently used antibiotics is becoming a public health issue; hence, the discovery of new antimicrobial agents from natural sources attracts a lot of attention. Antibacterial activities of oligogalacturonide from commercial microbial pectic enzyme (CPE) treated citrus pectin, which exhibits antioxidant and antitumor activities, against 4 foodborne pathogens including Salmonella Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas aeruginosa was assessed. Pectin hydrolysates from CPE hydrolysis exhibited antibacterial activities. However, no antibacterial activity of pectin was observed. Citrus oligogalacturonide from 24-h hydrolysis exhibited bactericidal effect against all selected foodborne pathogens and displayed minimal inhibitory concentration at 37.5 μg/mL for P. aeruginosa, L. monocytogenes, and S. Typhimurium, and at 150.0 μg/mL for S. aureus., (© 2014 Institute of Food Technologists®)

The antioxidant activity of pectic enzyme treated pectin (PET-pectin) prepared from citrus pectin by enzymatic hydrolysis and its potential use as a stabilizer and an antioxidant for soy protein isolate (SPI)-stabilized oil in water (O/W) emulsion were investigated. Trolox equivalent antioxidant capacity (TEAC) was found to be positively associated with molecular weight (M(w)) of PET-pectin and negatively associated with degree of esterification (DE) of PET-pectin. PET-pectin (1 kDa and 11.6% DE) prepared from citrus pectin after 24 h of hydrolysis by commercial pectic enzyme produced by Aspergillus niger expressed higher α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity, TEAC, and reducing power than untreated citrus pectin (353 kDa and 60% DE). The addition of PET-pectin could increase both emulsifying activity (EA) and emulsion stability (ES) of SPI-stabilized O/W emulsion. When the SPI-stabilized lipid droplet was coated with the mixture of PET-pectin and pectin, the EA and ES of the emulsion were improved more than they were when the lipid droplet was coated with either pectin or PET-pectin alone. The amount of secondary oxidation products (thiobarbituric acid reactive substances) produced in the emulsion prepared with the mixture of SPI and PET-pectin was less than the amount produced in the emulsion prepared with either SPI or SPI/pectin. These results suggest that PET-pectin has an emulsion-stabilizing effect and lipid oxidation inhibition ability on SPI-stabilized emulsion. Therefore, PET-pectin can be used as a stabilizer as well as an antioxidant in plant origin in SPI-stabilized O/W emulsion and thus prolong the shelf life of food emulsion.

The optimal conditions for the de-esterification reaction of tomato pectinesterase (PE) and citrus PE was 0.1-0.2 M NaCl and at pH 7.5-8.5, 65 degrees C, almost identical to those for the transacylation reaction as observed by turbidity (absorbance at 400 nm) change. Among the PEs tested, pea pod PE presented the most remarkable catalysis on the transacylation reaction, and 1.5% pectin solution was determined to be suitable for this reaction. Low methoxy pectin with a DE (degree of esterification) of 31% displayed a slow turbidity increase, revealing that the extent of DE was influential on the transacylation. Besides citrus pectin, apple pectin was also proved to progress transacylation reaction by PEs from tomato and citrus sources as apparently observed by turbidity method.

The changes in molecular masses of pectin in 0.5% pectin-pectinesterase (PE) mixtures (2 units/mL) incubated at various temperatures, pH values, and NaCl levels for 30 min were observed by a Toyopearl TSK HW-65 (F) gel permeation chromatography. The molecular mass of pectin was remarkably increased from 103 to 266 kDa when the incubation temperature of pectin-tomato PE was increased from 25 to 45 degrees C. A further increase in molecular mass was observed when a pectin-citrus PE mixture was incubated at 65 degrees C. The values of pH and NaCl levels were also crucial to the transacylation activity of PEs. Reaction at pH 7.5 with tomato PE and citrus PE remarkably expanded the molecular mass of pectin to 410 and 670 kDa, respectively. The NaCl level of 0.3-0.5 and 0.3 M was favorable for the transacylation reaction of tomato PE and citrus PE, respectively. Only high methoxylpectin was the suitable substrate for PE to conduct the transacylation reaction.

Abstract: Anti-tumour activity and membrane permeability of 1kDa oligogalacturonide (PET-pectin), prepared from citrus pectin after 24h hydrolysis, by commercial pectic enzyme produced by Aspergillus niger, on four human cell lines (HepG2, A549, Colo 205, and HEK293) and the uptake of oligogalacturonide by HEK293 cell and BALB/c mouse were investigated. PET-pectin causes a higher value of growth inhibition, lactate dehydrogenase release, and galactin-3 release in human cancer cells, as compared to the human normal HEK293 cell. There was a good correlation between growth inhibition of human cells and the uptake of rhodamine B-PET-pectin content by these cells. Additionally, almost no difference between growth inhibitions of human normal HEK293 cells cultivated with PET-pectin and pectin was found. Total pectin content in the blood of PET-pectin administrated mice increased to a maximum at 2h after oral administration, while it did not increase and change in pectin administrated mice. Our findings suggested that citrus PET-pectin can be developed as a potential dietary supplement in plant origin for cancer prevention. [Copyright &y& Elsevier]

Degree of esterification of pectin from jelly fig (Ficus awkeotsang Makino) achene seeds and the pH value decreased rapidly during extraction, while apparent reduction of free calcium content in the pectin extract was observed at the gelling stage. Compared to those of the native pectin, total ester linkages and methyl ester linkages of pectin extract decreased, and the bound calcium content increased during pectin gelling. However, non-methyl ester linkages (the difference between the total ester linkage and the methyl ester linkage) increased by approximately 40% during pectin gelling, revealing esterification reaction between C6 carboxyl groups and hydroxyl groups in the presence of pectinesterase. Scanning electron microscopy showed that pectin fragments from jelly curds were large with flake-like structure, while those from hot (85°C) ethanol-treated achenes were small and porous. [Copyright &y& Elsevier]