New insight into pectic fractions of cell wall: Impact of extraction on pectin structure and in vitro gut fermentation.

Pectic polysaccharides modulate gut fermentation ability, which is determined by structural characteristics. In this work, apple pectins were extracted by HCl (HAEP), NaOH (AEP), cellulase (EAEP), and in parallel cell wall pectic fractions were sequentially extracted by water (WEP), chelator (CEP) and NaOH (NEP). The aim is to comprehensively compare the impact of extraction on pectin structure and gut fermentation behavior. Results showed that high content of galacturonic acid (90.65 mol%) and large molecular weight (675 kg/mol) were detected in the HAEP. Molecular morphology of the HAEP presented high linearity, while AEP, EAEP and WEP exhibited compact filamentous structures with highly branched patterns. The AEP was characterized by high yield (33.1 g/100 g d.b.), moderate molecular weight (304 kg/mol) and large extent of rhamnogalacturonan-I region (24.88 %) with low degree of branching (1.77). After in vitro simulated gut fermentation for 24 h, total content of short-chain fatty acid (SCFA) generated with the AEP supplement increased to 36.8 mmol/L, followed by EAEP, HAEP and WEP (25.2, 24.2 and 20.3 mmol/L, respectively). Meanwhile, WEP simultaneously produced the highest ammonia content (22.4 mmol/L). This investigation suggests that the fermentation of AEP produces more beneficial SCFA and less ammonia, thus indicating a better gut fermentation property.

Effect of high pressure homogenization on water-soluble pectin characteristics and bioaccessibility of carotenoids in mixed juice.

The effect of high pressure homogenization (HPH) compared with simple blending and milling on mixed juice properties, including water-soluble pectin (WSP) characteristics and total carotenoid bioaccessibility (TCB) was investigated. Overall, HPH treatments, which comprised of varied pressures, passes and inlet temperature (IT) affected WSP characteristics. Increased pressure showed decreased molecular weight (Mw), galacturonic acid (GalA) content and branching, and enhanced degree of methylesterification (DM) and chain linearity, suggesting degradation of RG-I fragments. Two passes at 140 MPa enhanced GalA content, nevertheless it reduced DM, implying rearrangement of depolymerized fractions. Besides, elevated IT combined with high pressure increased GalA content and DM signifying thermo-solubilization of certain HG-rich pectin. Notably, the TCB was enhanced by higher pressure and elevated temperature, which had positive relationship with DM and chain linearity of WSP and negative correlations with GalA content and Mw. Results highlighted the potential of HPH to improve WSP characteristics to enhance TCB.

Pectin and homogalacturonan with small molecular mass modulate microbial community and generate high SCFAs via in vitro gut fermentation.

The intestinal fermentability of pectic polysaccharides is largely determined by its molecular size. In this study, fermentation properties of enzymatic-modified apple pectin (AP) and homogalacturonans (HG) with high, medium and low molecular weight (Mw) were evaluated by in vitro fermentation model, and their structural changes were also investigated. Results showed that Mw, monosaccharide contents and molecular linearity of the AP hydrolysates were reduced after microbial degradation. On the other hand, culture media supplemented with low-Mw AP (60,300 g/mol) and low-Mw HG (861 g/mol) exhibited lower pH (5.1 and 5.7, respectively) and produced higher total short-chain fatty acid contents (SCFA, 230.40 mmol/L and 187.19 mmol/L, respectively). However, reduced trends in abundance of the pectinolytic microorganisms Faecalibacterium and Eubacterium were showed as Mw of the HG decreased, whereas growth of the SCFA-producer genera Bifidobaacterium, Megasphaera and Allisonella were improved. This work confirmed that low-Mw pectin and homogalacturonan generated more beneficial metabolites, developing structure-microbiota-gut health relationship.

Systematic Review of Phenolic Compounds in Apple Fruits: Compositions, Distribution, Absorption, Metabolism, and Processing Stability.

As the most widely consumed fruit in the world, apple (Malus domestica Borkh.) fruits provide a high level of phenolics and have many beneficial effects on human health. The composition and content of phenolic compounds in natural apples differs according to the tissue types and cultivar varieties. The bioavailability of apple-derived phenolics, depending on the absorption and metabolism of phenolics during digestion, is the key determinant of their positive biological effects. Meanwhile, various processing technologies affect the composition and content of phenolic compounds in apple products, further affecting the bioavailability of apple phenolics. This review summarizes current understanding on the compositions, distribution, absorption, and metabolism of phenolic compounds in apple and their stability when subjected to common technologies during processing. We intend to provide an updated overview on apple phenolics and also suggest some perspectives for future research of apple phenolics.

Bioaccessibility of carotenoids and antioxidant capacity of seed-used pumpkin byproducts powders as affected by particle size and corn oil during in vitro digestion process.

Powders made from seed-used pumpkin flesh (SUPF) are potential sources of carotenoids. In this study, unexplored effects of particle size and corn oil on bioaccessible amounts of carotenoids and antioxidant capacity of SUPF powders during in vitro digestion process were investigated. Overall, total carotenoid relative bioaccessibility (TCRB) of 100 mesh-sized powder (100 MP, 15.46%) was higher than that of 18 mesh-sized powder (18 MP, 12.94%). With the addition of 2% corn oil, TCRB increased 108.35% (18 MP) and 88.55% (100 MP), respectively. Lutein (≥27160 µg/100 g) and ß-carotene (≥5192 µg/100 g) were main carotenoid monomers in SUPF and significantly correlated with DPPH radical scavenging activity of digestive supernatant (p < 0.05). Notably, DPPH radical scavenging activity of 18 MP increased 96.54% with corn oil. These results implied that smaller particle size and oil addition could improve bioaccessible amounts of carotenoids and antioxidant capacity of SUPF powders.

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.

Characteristics of cell wall pectic polysaccharides affect textural properties of instant controlled pressure drop dried carrot chips derived from different tissue zone.

To better understanding the role of cell wall pectic polysaccharides (CWPs) on the formation of textural properties of carrot chips dried by instant controlled pressure drop technology (French for Détente Instantanée Contrôlée, DIC), the characteristics of CWPs from ground tissue (GT), junction of ground and vascular tissue (JT), and vascular tissue (VT) of carrot were investigated. Larger expansion volume was obtained in the carrot chips derived from GT, which accompanied with superior textural qualities compared with the chips derived from JT and VT. Remarkable differences were obtained in the amount of pectic fractions, galacturonic acid content, degree of methoxylation, sugar composition and linearity of CWPs that fractionated from different tissue zones of raw carrots. The characteristics of CWPs was confirmed to be a substantial factor that significantly affected the expansion ratio and textural properties of the DIC-dried carrot chips, which providing a mechanistic insight of the relationship between variation in CWPs and the expanding behaviors of DIC-dried fruits and vegetables.

Effects of high pressure homogenization and addition of oil on the carotenoid bioaccessibility of carrot juice.

Food processing and dietary lipids are considered as important factors for carotenoid bioaccessibility. The effects of high pressure homogenization (HPH) combined with oil or emulsion on carotenoid retention and bioaccessibility during digestion were investigated. The results illustrated that HPH decreased the area-based diameter (D[3,2]), and negative correlations were found between the total carotenoid bioaccessibility (TCB) and D[3,2] of carrot juice. The bioaccessibility of total carotenoids, ß-carotene and α-carotene of the homogenized samples was below 6%, while the addition of 2% oil, 10% oil or emulsion increased the carotenoid bioaccessibility (up to 14.08% for α-carotene). The carotenoid retention rate (CRR) of the homogenized samples was higher than that of the homogenized samples with oil or emulsion in each digestion phase. The CRR in the small intestine phase had a significant negative correlation with TCB, and therefore, a high TCB could be achieved despite a low CRR in the small intestine. Oil added as an emulsion had a slightly higher volume of free fatty acids released compared with oil added as such.

Determination of phenolic compounds and antioxidant activities from peel, flesh, seed of guava (Psidium guajava L.).

White-flesh guava is widely planted in tropical or subtropical areas of Southeast Asia. Despite of folk statements on specific function, few researches are focused on the description of its plant secondary metabolites. In the present work, contents of total phenolics and flavonoids as well as antioxidant activity from different parts (peel, flesh, and seed) were determined. The constituents of ethanol extracts were characterized by HPLC-QTOF-MS. A total of 69 phenolic compounds as well as nine polar compounds were detected, with flavonoids, hydrolyzable tannins, phenolic acid derivatives, and benzophenones of the four predominant phenolic compounds. Moreover, the presence of other phenolics (lignan, phenylethanoid, stilbenoid, and dihydrochalcones) was revealed. Simultaneously, the polar compounds, such as triterpenoids, iridoid were identified. Benzophenones and triterpenoids were proved to be marked constitutes of peel and flesh, respectively. The existence of isoflavonoids, lignan, phenylethanoid were firstly reported for edible parts or by-products of guava. The results showed that white-flesh guavas, particularly peel parts, were superior resources of antioxidant compounds, with exploitation value.