The combination of atomic force microscopy and sugar analysis to evaluate alkali-soluble Canna edulis Ker pectin

Preparation and structure-function relationships of homogalacturonan-rich and rhamnogalacturonan-I rich pectin: A review

Pectin has multiple functions and is widely used in the food industry. It is an acidic heteropolysaccharide found in most plants, mainly consisting of two regions: homogalacturonan (HG) and rhamnogalacturonan-I (RG-I). HG and RG-I rich pectin have unique structures and functional properties, which can be obtained through specific preparation methods. Some emerging physics assisted preparation strategies are more advantageous for preparing specific structures with higher purity and efficiency than traditional preparation methods. HG and RG-I rich pectin have unique processing and functional properties, but sometimes a proper ratio of HG and RG-I pectin may have better effects than individuals. Therefore, it is speculated that there may be some synergistic effects between the two pectin structures. A comprehensive understanding of the preparation, structure, and functional relationship of HG and RG-I rich pectin is crucial for the efficient preparation of pectin with targeted functions.

The instability of pectin-based emulsions in the upper digestive tract investigated based on the molecular structure and interfacial properties of pectin

Pectin is a widely used natural emulsifier that is thought to stabilize emulsions in the upper gastrointestinal tract (GIT). However, changes in the structural characteristics and interfacial properties of pectin during its digestive treatment in the upper GIT and the effects on the stability of pectin-based emulsions are still unclear. This study showed that the stability of pectin-based emulsions steadily decreased in the upper GIT. Reductions in the molecular weight of pectin (from 2.74× 105 to 1.61× 105 g/mol) occurred mainly in the stomach, whereas the degree of esterification (from 61.2 % to 42.1 %) decreased throughout the digestive treatment. The change in the structure of pectin reduced its hydrophobicity in the upper GIT, and led to form a cross-linked network with Ca2+ in small intestine rather than adsorbing to the oil-water interface. The behavior was reflected in the increased interfacial tension and the decreases in the interfacial modulus and thickness of pectin. Our insights into the structural characteristics and interfacial properties of pectin and thus into the mechanism of pectin instability in the upper GIT will contribute to the development of more efficient encapsulation methods and improved targeted delivery for active substances or probiotics using pectin-based emulsions.

Impact of pre-meal immersion on multi-scale structural changes and starch digestibility of cooked dried noodles

Pre-meal immersion is a common process for both the consumption of dried noodles and development of takeaway noodles, but its impact on the structure and digestibility of dried noodles is still unclear. In this study, dried noodles cooked for the optimal time were immersed at 80 °C for different time durations. Multi-scale structural changes, including texture, molecular structure, microstructure, and in vitro starch digestibility were studied using a combination of kinetic (first-order exponential decay function, the Peleg model, and LOS plots), physicochemical, and microscopic analysis. The relationship between multi-scale structural changes and starch digestibility was derived. As the immersion progressed, the hardness first rapidly decayed and then reached equilibrium. The decay rate in the initial stage depended on the gluten content. In most cases, the immersion process caused depolymerization of gluten proteins and further gelatinization of starch granules, which was observed from an increase in the free -SH content and decrease in the short-range ordered structure, although there were fluctuations over immersion time. Structural changes resulted in the corresponding changes in substance migration. However, a high gluten content (∼15% w/w) imparted a denser microstructure to the noodles, weakening the deterioration effects compared with a low gluten content (∼10% w/w). In vitro digestion experiments proved that samples with higher gluten content had higher starch digestion rates and lower starch digestion extent during immersion. Correlation analysis revealed that there was a negative correlation between k1 and the tightness of the gel. This study helps to reveal the structural mechanisms of starch digestibility in cooked noodles during immersion.

Mechanism for gel formation of pectin from mealy and crisp lotus rhizome induced by Na+ and D-glucono-d-lactone

Lotus rhizome residue, a cell wall material produced during the production of lotus rhizome starch, has long been underutilized. This study aims to extract pectin-rich polysaccharides from the cell wall of lotus rhizome and investigate their gelation mechanism in order to improve their industrial applicability. The results indicated that both CP and MP (pectin extracted from crisp and mealy lotus rhizome) exhibited a highly linear low methoxyl pectin structure, with the primary linkage mode being →4)-GalpA-(1→. The pectin chains in MP were found to be more flexible than those in CP. Then the impact of Na+, D-glucono-d-lactone (GDL), urea, sodium dodecyl sulfate (SDS), either individually or in combination, on the rheological characteristics of gels was evaluated. The results indicated that gels induced by GDL exhibited favorable thermoreversible properties, whereas the thermoreversibility of Na+-induced gels is poor. In addition to hydrogen bonding and ionic interactions, hydrophobic interactions also play a significant role in the formation of pectin gels. This study offers theoretical guidance and methodologies to improve the utilization rate of lotus rhizome starch processing by-products, while also provides novel insights into the correlation between LMP structure and gelation mechanism.

Effects of ripening stage on physicochemical properties, drying kinetics, pectin polysaccharides contents and nanostructure of apricots

Effects of ripeness (four stages from the lowest to highest degree-I, II, III, and IV) on the physicochemical properties, pectin contents and nanostructure, and drying kinetics of apricots were investigated. The color values (L^*, a^*, and b^*) and total soluble solid content increased during ripening, while the titratable acidity content and hardness decreased. The water-soluble pectin content increased as ripening progressed, but the chelate- and sodium carbonate-soluble pectin contents gradually declined. Atomic force microscopy imaging indicated that the pectin depolymerization occurred during ripening. Fruits at stage III obtained the highest drying rate, and the drying time was reduced by 27.27%, 17.24%, and 7.69% compared to those of stage I, II and IV, respectively. Results showed that the ripeness had significant influence on the drying kinetics, which is related to the modification of physicochemical and pectic properties. The ripeness classification is an essential operation for achieving effective drying process.