为了研究不同多元糖浸渍处理对冻干苹果片品质特性及微观孔隙结构的影响,分别采用质量分数为0、5%、10%、15%、20%、25%的多元糖(葡萄糖、蔗糖、水苏糖及木糖醇)对苹果片进行浸渍处理,测定冻干苹果片色泽、产出率、复水比、形变率、质地特性及微观孔隙结构的变化。结果表明,多元糖可使冻干苹果片L*值显著下降,ΔE值和产出率显著增加(P<0.05);随着多元糖质量分数的增加,冻干苹果片复水比基本呈先增加后减少的趋势,除了水苏糖,其他多元糖浸渍冻干苹果片形变率逐渐增加;葡萄糖浸渍冻干苹果片结构坍塌,细胞结构发生了皱缩和变形,孔壁增厚,表现出较高的硬度、较大变形率及较低的孔隙率;蔗糖浸渍的冻干苹果片结构坍塌更严重,孔隙更小,表现出较低的孔隙率及较大的变形率;木糖醇浸渍的冻干苹果片细胞结构有些皱缩和坍塌,不具有其他糖赋予细胞结构的厚实感,表现出较差的质地特性及较大变形率;水苏糖浸渍的冻干苹果片细胞组织结构规整蓬松,孔隙均匀,孔壁较厚,促使了冻干苹果片具有较高的孔隙率、较低的变形率及较好咀嚼性和回复性的质构特性。该研究结果发现了水苏糖可以有效提高冻干苹果片的综合品质,揭示了冻干苹果片品质变化与微观孔隙结构变化有关,为改善冻干水果制品品质提供了一定的理论依据。
The fresh-cut apple slices were impregnated with 0, 5%, 10%, 15%, 20% and 25% (mass fraction) of polysaccharide including glucose, sucrose, stachyose and xylitol. After freeze-drying, the properties of the dried products were analyzed, including color, yield, rehydration, deformation rate, texture characteristics and microscopic pore structure. The results showed that the polysaccharides significantly reduced the L* value of freeze-dried apple slices, and significantly increased the ΔE value and yield rate (P<0.05). The rehydration ratio increased first and then decreased, the deformation rate increased with the increasing of the polysaccharide concentration except for stachyose. The structure of glucose-impregnated freeze-dried apple slices collapsed and deformed, and the pore walls were thickened, resulting in higher hardness and deformation rate, as well as lower porosity. The structure of sucrose-impregnated freeze-dried apple slices collapsed more severely, and the pores were smaller, resulting in lower porosity and larger deformation rate. Xylitol-impregnated freeze-dried apple slices showed some shrinkage and collapse, with no solid texture of the cell structure caused by other sugars, exhibiting poor texture characteristics and large deformation rate. Stachyose-impregnated freeze-dried apple slices showed regular structure, with uniform pores and thicker pore walls, which contributed to the high porosity, low deformation rate, good chewiness and recovery characteristics of the freeze-dried apple slices. It was found that stachyose could effectively improve the comprehensive quality of freeze-dried apple slices. This paper revealed the correlation between the quality and microscopic pore structure, providing a theoretical basis for improving the quality of freeze-dried fruit products.
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