Impact of sodium ions on material properties, gelation and storage stability of citrus pectin

Effect of calcium chloride and gelling agents on the physicochemical and sensory characteristics of sugar-free banana preserves

Banana preserve is produced by mixing the puree of the fruit with sucrose and organic acids. However, concerns about body esthetics or health reasons have encouraged the search for low-calorie products. Therefore, the objective of this study was to evaluate the effect of calcium chloride (CaCl2), carrageenan gum, and low methoxyl pectin (LM-pectin) on the physicochemical and sensory characteristics of sugar-free banana preserves. By using a central composite rotational design (CCRD) of 2³ + 6 axial points + 4 central points, we obtained 18 formulations that were further tested. Lower CaCl2 concentrations (0.54% to 0.61%) resulted in preserves with lower pH and more vivid color. The increased concentration of LM-pectin (1.40% to 1.64%) resulted in formulations with a yellowish-red hue and with lower moisture, thus, reducing the flavor and purchase intention of the product. Higher concentrations of carrageenan gum (1.04% to 1.15%) decreased the perception of banana preserve aroma. Therefore, concentrations of CaCl2 ranging from 0.54% to 0.61%, carrageenan gum ranging from 0.74% to 0.89% and LM-pectin ranging from 1.40% to 1.64% resulted in sugar-free banana preserves with ideal sweetness and consistency and were, therefore, more acceptable.

Influence of the Carboxylic Function on the Degradation of d-Galacturonic Acid and Its Polymers

Past investigations have shown high browning potential during the caramelization of sugar acids in comparison to reducing sugars. However, no approaches to elucidate the chemical mechanisms have been made. Therefore, this study aims to clarify the reasons for the high browning potential by measuring the mutarotation velocity and the elimination of CO₂ during the heat treatment of uronic acids. Performed polarimetric experiments show that the mutarotation velocity of d-galacturonic acid exceeds that of d-galactose by a factor of nearly 4.5. However, the ring opening velocity is not the only parameter that differs between the two carbohydrate structures. Measurements of the release of CO₂ of heated d-galacturonic acid at 60 °C show a steady increase, and after 48 h, 6% of degraded d-galacturonic acid has eliminated CO₂. CO₂ release was also found during the heating of pectin, indicating a decarboxylation reaction during thermal degradation. One of the degradation reactions postulated for the release of CO₂ leads to α-ketoglutaraldehyde, which is responsible for the formation of several chromophoric substances.

Production and molecular characterization of tailored citrus pectin-derived compounds

In this study, tailored-made citrus pectin-derived compounds were produced through controlled enzymatic and/or chemical modifications of commercial citrus pectin with different degrees of methylesterification (DM) and similar average molecular weight (M_W). In the first treatment, degradation of the citrus pectin (CP) materials by endo-polygalacturonase (EPG) yielded pectins with average M_w's (between 2 and 60 kDa). Separation and identification of the oligosaccharide fraction present in these samples, revealed the presence of non-methylesterified galacturonic acid oligomers with degree of polymerization (DP) 1-5. In the second treatment, exploiting the combined effect of EPG and pectin lyase, compounds with M_W between 2 and 21 kDa, containing methylesterified and non-methylesterified polygalacturonans (DP 1-6), were generated. Finally, CP was sequentially modified by chemical saponification and the action of EPG. A sample of DM 11% and M_W 2.7 kDa, containing POS (DP 1-5), was produced. Diverse pectin-derived compounds were successfully generated for further studies exploring their functionality.

The relationship between fluoride accumulation in tea plant and changes in leaf cell wall structure and composition under different fluoride conditions

Tea plant is capable of hyper-accumulating fluoride (F) in leaves, suggesting drinking tea may cause excessive F intake in our body and threaten the health. This study investigated the changes in the structure, composition, and F content in the leaf cell wall of the tea (Camellia sinensis) under different F conditions to demonstrate the role of cell wall in F enrichment in tea plants. The cell wall was shown as the main part for F accumulation (67%-92%), with most of F distributed in the pectin fraction (56%-71%). With increasing F concentration, a significant increase (p < 0.05) was observed in the F content of cell wall and its components, the level of cell wall metal ions (i.e. Cu, Mg, Zn, Al, Ca, Ba, Mn), as well as the content of total cell wall materials, cellulose, and pectin. Meanwhile, the level of Cu, Mg, Zn, pectin, and cellulose was significantly positively correlated with the F content in the leaf cell wall. F addition was shown to increase the fluorescence intensity of LM19 and 2F4 antibody-labeled low-methylesterified homogalacturonans (HGs), while decrease LM20-labeled high-methylesterified HGs, coupled with an increase in the activity and gene expression of pectin methyl esterases (PMEs) in tea leaves. All these results suggest that F addition can increase pectin content and demethylesterification, leading to increased absorption of metal cations and chelation of F in the cell wall through the action of metal ions.