复合助剂对低温喷雾干燥蓝靛果粉理化性质的影响

    Effects of compound additives on the physicochemical properties oflow-temperature spray drying Lonicera edulis powder

    • 摘要: 为保证低温喷雾干燥后蓝靛果粉品质,采用黄金分割法研究复合助剂(麦芽糊精、β-环糊精和乳清蛋白)对喷雾干燥蓝靛果粉理化性质的影响,分析低温进风温度(50~90 ℃)对蓝靛果粉花青素保留率、集粉率和含水率的影响规律。结果表明,在麦芽糊精、β-环糊精的质量比例为85.4%、14.6%时,集粉率高达37.96%;随进料溶液中麦芽糊精质量比例增加,蓝靛果粉玻璃化转变温度、水溶性指数、堆积密度、亮度L*值、红度a*值和色差值ΔE呈增加趋势,含水率、花青素含量和黄度b*值呈下降趋势;在麦芽糊精、β-环糊精和乳清蛋白质量比例为72.9%、12.5%、14.6%时,集粉率达到最高(40.11%);随料液中乳清蛋白质量比例增加,蓝靛果粉含水率、花青素含量呈上升趋势,其玻璃化转变温度、水溶性指数、亮度L*值、红度a*值、黄度b*值和色差值ΔE等指标呈下降趋势;复合助剂显著提高蓝靛果粉集粉率(P<0.05),对其中的花青素起到较强保护作用,其含水率、水溶性指数、堆积密度等理化指标均接近于最优水平。低温喷雾干燥研究发现,随进风温度上升,集粉率和含水率呈负相关,在进风温度90 ℃时,集粉率最高的配方中可实现较高花青素保留率(89.94%)。低频核磁共振波谱以及质子密度图像信息分析表明,加入的助剂与蓝靛果果汁中水分通过氢键、静电结合力和疏水作用等分子间作用力,形成稳定性高水合物、增强液滴聚结抵抗力,提高料液玻璃态转换温度,从而实现高集粉率和高花青素保留率的蓝靛果果粉低温喷雾干燥;红外光谱分析表明,复合助剂可在蓝靛果果粉中形成分子间氢键,并对花青素等活性物质进行固定包埋保护。研究结果可为蓝靛果粉喷雾干燥加工生产提供理论支撑和参考依据。

       

      Abstract: This study aims to improve the quality of spray-drying Lonicera edulis powder. Maltodextrin, β-cyclodextrin and whey protein were used as the compound additives. A systematic investigation was implemented to clarify the effects of compound additives on the physicochemical properties of spray-drying Lonicera edulis powder. The golden split formulation test was designed as a single-factor test. An analysis was made on the effects of low-temperature air inlet temperature (50-90 °C) on anthocyanin retention rate, powder collection rate, and water content of Lonicera edulis powder. The results show that the powder collection rate was as high as 37.96% in the first golden split formulation test, when the mass ratios of maltodextrin and β-cyclodextrin were 85.4% and 14.6% (test point T4), respectively. There was an increasing trend in the glass transition temperature (Tg), water solubility index, bulk density, L* value, a* value, and color difference ΔE of Lonicera edulis powder, with the increase in the mass ratio of maltodextrin in the feed solution, while the water content, anthocyanin content, and b* value showed a decreasing trend. A comparison was then made on the physicochemical index of each test point in the first golden split. The test point T4 was selected for the second golden split formulation test; The highest powder collection rate (40.11%) was achieved, when the ratios of maltodextrin, β-cyclodextrin and whey protein were 72.9%, 12.5%, and 14.6% (test point E4), respectively. The contents of water and anthocyanin tended to increase in the prepared Lonicera edulis powder, with an increase in the proportion of whey protein in the feed solution, while there was a decrease in the glass transition temperature (Tg), water solubility index, L* value, a* value, b* value and color difference ΔE. A comparison was also made on the physicochemical indexes of single additive T6 (maltodextrin mass ratio of 100%), T7 (β-cyclodextrin mass ratio of 100%), E7 (whey protein mass ratio of 100%), the best composite additives T4 (in the first golden section), and E4 (in the second golden section) test points. The composite additives significantly improved the powder collection rate of Lonicera edulis powder via a synergistic effect (P<0.05). The physical and chemical indexes (such as water content, water solubility index, and bulk density) were all close to the optimum level, indicating that the composite additives improved the comprehensive quality of Lonicera edulis powder better than that of a single additive. The additives in the feed solution shared their physical and chemical properties during spray drying and then interacted with each other with the biological activity. The low-temperature spray drying test showed that the powder collection rate and water content were negatively correlated with the increase in inlet air temperature. The test site E4 presented a high anthocyanin retention rate (89.94%) while maintaining a high powder collection rate at 90oC. The spectral and proton density images were captured in the Lonicera edulis stock and sample solution at each test site. Additives were added to increase the content of strong bound water, weak bound water and immobile water in the feed and liquid. The freedom of free water was also reduced for the stable hydrate, in order to improve the droplet coalescence resistance, the overall Tg of feed and liquid, and the powder collection rate. The water distribution of the sample solution was much more uniform, while the whole solution was more stable after pretreatment with compound and single additive, which was conducive to the preparation of blue Lonicera edulis powder by spray drying. Fourier transform infrared spectroscopy (FTIR) analysis showed that the compound additives formed the intermolecular hydrogen bonds in Lonicera edulis powder, thus protecting the anthocyanins and other active substances. The findings can provide theoretical support and reference for the production of Lonicera edulis spray drying.

       

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