玛咖可溶性膳食纤维的制备及其表征

Preparation and Characterization of Soluble Dietary Fiber from Maca

采用碱提条件制备榨汁后的玛咖渣中玛咖可溶性膳食纤维(SDF),以响应曲面法优化最佳工艺参数,并对制备产物的单糖种类、平均聚合度等理化指标进行表征。结果表明:碱提法制备玛咖SDF的最佳工艺条件为NaOH质量分数9%、提取温度90℃、提取时间79min、料液比1:48(g/mL),在此条件下,玛咖SDF得率为52.6%,与预测值(53.0%)偏差为0.0076,说明实际值与预测值的一致性较好;X射线衍射测定玛咖SDF的结晶度为69.05%,红外光谱图显示具有其吸收峰,由阿拉伯糖、甘露糖、半乳糖、鼠李糖、木糖、葡萄糖6种单糖组成,黏均分子质量约为39471g/mol,数均分子质量约为48589g/mol,平均聚合度为299;玛咖SDF外观呈现不规则,具有较大的空隙,膨胀力为2mL/g,对油脂的吸附能力较强,1g玛咖SDF能吸附2.69g玉米油。

The maca residue left after juice extraction, though rich in dietary fiber including soluble and insoluble fibers, is often regarded as a waste material. Soluble dietary fiber （SDF） is believed to be beneficial to human health. In the present study, response surface methodology was employed to optimize the conditions for alkali extraction of SDF from maca residue and some physiochemical properties of the resulting SDF were characterized such as monosaccharide composition and average degree of polymerization. As a result, the optimum conditions are found to be to be 9%, 90 ℃, 79 rain and 1：48 for alkali concentration, temperature, extraction time and solid-to-liquid ratio, respectively. The actual yield of SDF under the optimized conditions was 52.6%, which is in close agreement with the predicted one （53.0%） with a deviation of 0.0076. The crystallinity of maca SDF was 69.05% as examined by X-ray diffraction. Some typical absorption peaks of the SDF were analyzed by PTIR. The SDF was made up of six monosaccharides including arabinose, mannose, galactose, rhanmose, xylose and glucose. Viscosity-average and number-average molecular weights were approximately 39471 g/tool and 48589 g/mol, respectively. Its average degree of polymerization was 299. In addition, irregular appearance was also observed together with large holes in its interior structure and its expansive force was 2 mL/g. Moreover, the oil-absorbing capacity was good, absorbing 2.69 g of corn oil per g of maca SDF.