Abstract
Date fruits vary widely in the hardness of their edible parts and they are classified accordingly into soft, semi-dry, and dry varieties. Fruit texture, a significant parameter in determining consumer acceptance, is related to the tissue structure and chemical composition of the fruit, mainly the ratio of sucrose to reducing sugars. This study aimed to understand the relationship between the chemical composition, microstructure, and texture profile of 10 major Emirati date fruits. The soluble sugars, glucose and fructose, represent ca 80 g/100 g of the fruits on the basis of dry weight (DW) while the dietary fiber contents varied 5.2–7.4 g/100 dg D.W. with lignin being the main determinant of the variability. The textures of the samples were studied using instrumental texture profile analysis. While no correlation was found between the soluble sugar and texture parameters in this study, the different fiber constituents correlated variably with the different parameters of date fruit texture. Lignin, arabinoxylan, galactomannan, and pectin were found to correlate significantly with fruit hardness and the related parameters, gumminess and chewiness. Both lignin and arabinoxylan correlated with resilience, and arabinoxylan exhibited a strong correlation with cohesiveness.
Highlights
Date fruits vary widely in the hardness of their edible parts and they are classified into soft, semi-dry, and dry varieties
A considerable variation was observed in the other dietary fiber components like fructans (0.1–0.5%) and other neutral sugar from gas chromatography (GC) values of dietary fibers such as glucose (1.2–1.5%), arabinose (0.3%), xylose (0.7–1.1%), galactose (0.3–0.7%), mannose (0.2%), and uronic acids (0.8–1.1%) constituting cellulose/β-glucan (1.2–1.5%), arabinoxylan (1–1.4%), and galactomannan (0.5–0.9%)
This structural variation in date fruits is mainly governed by the concentrations of the different fiber constituents and sugar types
Summary
Date fruits vary widely in the hardness of their edible parts and they are classified into soft, semi-dry, and dry varieties. Date fruits at full maturity Tamr stage are primarily composed of sugars (60–80%) with the rest of the weight being moisture (10–30%), dietary fiber (5–12%), phenolic compounds (up to 4%), and other minor constituents on a fresh weight basis[2] As they are variable in their moisture contents, date fruits are classified as soft (> 30% moisture), semi-dry (20–30% moisture), and dry (< 20% moisture) varieties on the basis of their moisture content. It has been shown that the nanostructure of pectin, hemicellulose, and cellulose in cell walls affects the texture and firmness of p ears[12] Microscopic analysis, such as light microscopy, can be employed to identify different tissue structures, such as phenolic compounds in the exocarp and mesocarp[9]. Understanding the texture profiles requires relating them to chemical composition, especially sugars and fibers, which are believed to influence texture, hardness, elasticity, and stickiness
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