Cell Wall Polymer Composition and Spatial Distribution in Ripe Banana and Mango Fruit: Implications for Cell Adhesion and Texture Perception

Abstract

Banana ( Musa acuminata ) and mango ( Mangifera indica ) are two of the most popular fruits eaten worldwide. They both soften during ripening but their textural attributes are markedly different. This study aimed to elucidate the molecular mechanism underpinning textural differences between banana and mango. We used a novel combination of methods at different scales to analyse the surface properties of fruit cells and the potential contribution of cells and cell wall components to oral processing and texture perception. The results indicated that cell separation occurred easily in both organs under mild mechanical stress. Banana cells showed distinctively elongated shapes with distinct distribution of pectin and hemicellulose epitopes at the cell surface. In contrast, mango had relatively spherical cells that ruptured during cell separation. Atomic force microscopy detected soft surfaces indicative of middle lamella remnants on banana cells, while mango cells had cleaner, smoother surfaces, suggesting absence of middle lamellae and more advanced cell wall disassembly. Comparison of solubilized polymers by cell wall glycome analysis showed abundance of mannan and feruylated xylan in separation exudate from banana but not mango, but comparable levels of pectin and arabinogalactan proteins. Bulk rheology experiments showed that both fruits had similar apparent viscosity and hence might be extrapolated to have similar “oral thickness” perception. On the other hand, oral tribology experiments showed significant differences in their frictional behavior at orally relevant speeds. The instrumental lubrication behavior can be interpreted as “smooth” mouthfeel for mango as compared to “astringent” or “dry” for banana in the later stages of oral processing. The results suggest that cell wall surface properties contribute to lubricating behavior associated with textural perception in the oral phase.

Plant Cell Walls: Impact on Nutrient Bioaccessibility and Digestibility

“…The size of the pore but also its conformation and flexibility govern the diffusion of a molecule through the cell wall. Cells, with intact walls, separated from plant tissues are becoming a popular tool to investigate the permeability of the cell walls and macronutrient digestibility [31][32][33][34][35][36][37][38][39][40][41]. These in vitro studies confirmed that digestive enzymes (α-amylase, proteases and pancreatic lipase) cannot diffuse through the cell wall of many plant-based foods (almond, wheat, chickpea, pea, mung bean, red kidney bean, and sorghum) whereas some cell wall appeared to be more permeable (common bean, potato tuber, banana and mango).…”

“…Particle size reduction also facilitated starch bioaccessibility and digestibility in legumes. Cooking of legumes promoted pectin solubilization, but contrary to fruits and vegetables, this led to cell wall swelling [34] and/or cell separation [70], similarly to cell wall disassembly observed during fruit ripening [40]. Cell walls that remain intact, such as those of separated cells, will prevent or slow down macronutrients digestion (see Section 2.3).…”

Fruit Characteristics, Peel Nutritional Compositions, and Their Relationships with Mango Peel Pectin Quality

“…Sections were stained with toluidine blue O solution in 0.1 M phosphate buffer (pH 6.8). The samples were observed using an inverted light microscope according to the modified method of Rongkaumpan et al [124].…”

Plasmodesmata and their role in the regulation of phloem unloading during fruit development

“…Scanning electron microscopy showed circular depressions with ridge-like features of 80–140 nm in width spaced at 300–350 nm [ 29 ]. Fluorescent imaging also revealed presumed PD connections in other fruits such as bananas and mangoes [ 41 ]. Calcofluor-white staining of cellulose in mature fruits revealed regions between parenchyma cells (PCs) that resemble pit fields in these fruits [ 41 ].…”