Abstract In this study, foamed raspberry puree was dried by microwave-assisted freeze drying (MWFD). The combined use of microwaves and a foamed structure was intended to accelerate the drying process, while creating an innovative product structure with intense aroma impact for consumption as a snack. The influence of potato protein as foaming agent, maltodextrin as foam stabilizer and microwave (MW) power on the drying characteristics of raspberry foams during MWFD was investigated. Conventional freeze drying (FD) experiments were performed as a reference. MD concentration was shown to significantly influence product temperature. As higher MD concentrations yielded smaller bubbles and a more uniform bubble size distribution, lower drying temperatures were needed to reach the same final moisture content. Varying MW power did not significantly influence the drying time. MWFD at 1.0 W g−1 yielded a 3–4-fold decrease in total drying time as compared to FD. The addition of 10% protein led to the most gentle drying at high MW power input due to structural changes enabling a lower resistance against water vapor mass transfer. There was a high correlation between the foam characteristics and the drying behavior. An overrun above 450% led to gentle drying at all tested microwave power input levels. Foam bubble size and bubble size distribution correlated well with drying velocity. Overall, MWFD was shown to be a much faster and more gentle alternative to FD for the production of fruit foams.

中文翻译：

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添加水胶体和微波处理条件对泡沫覆盆子果泥干燥行为的影响

摘要 本研究采用微波辅助冷冻干燥 (MWFD) 对泡沫覆盆子果泥进行干燥。微波和泡沫结构的结合使用旨在加速干燥过程，同时创造具有强烈香气影响的创新产品结构，作为零食食用。研究了马铃薯蛋白作为发泡剂、麦芽糊精作为泡沫稳定剂和微波 (MW) 功率对 MWFD 过程中覆盆子泡沫干燥特性的影响。进行常规冷冻干燥 (FD) 实验作为参考。MD 浓度显示出显着影响产品温度。由于较高的 MD 浓度产生较小的气泡和更均匀的气泡尺寸分布，因此需要较低的干燥温度以达到相同的最终水分含量。改变 MW 功率对干燥时间没有显着影响。与 FD 相比，1.0 W g-1 的 MWFD 使总干燥时间减少了 3-4 倍。添加 10% 的蛋白质可在高 MW 功率输入下实现最温和的干燥，这是因为结构变化能够降低对水蒸气传质的阻力。泡沫特性与干燥行为之间存在高度相关性。超过 450% 的溢出导致在所有测试的微波功率输入水平下温和干燥。泡沫气泡大小和气泡大小分布与干燥速度密切相关。总体而言，MWFD 被证明是一种更快、更温和的替代 FD，用于生产水果泡沫。添加 10% 的蛋白质可在高 MW 功率输入下实现最温和的干燥，这是因为结构变化能够降低对水蒸气传质的阻力。泡沫特性与干燥行为之间存在高度相关性。超过 450% 的溢出导致在所有测试的微波功率输入水平下温和干燥。泡沫气泡大小和气泡大小分布与干燥速度密切相关。总体而言，MWFD 被证明是一种更快、更温和的替代 FD，用于生产水果泡沫。添加 10% 的蛋白质可在高 MW 功率输入下实现最温和的干燥，这是因为结构变化能够降低对水蒸气传质的阻力。泡沫特性与干燥行为之间存在高度相关性。超过 450% 的溢出导致在所有测试的微波功率输入水平下温和干燥。泡沫气泡大小和气泡大小分布与干燥速度密切相关。总体而言，MWFD 被证明是一种更快、更温和的替代 FD，用于生产水果泡沫。泡沫气泡大小和气泡大小分布与干燥速度密切相关。总体而言，MWFD 被证明是一种更快、更温和的替代 FD，用于生产水果泡沫。泡沫气泡大小和气泡大小分布与干燥速度密切相关。总体而言，MWFD 被证明是一种更快、更温和的替代 FD，用于生产水果泡沫。