Time and energy reduction on grape dehydration by applying dipping solution on freeze drying process

Abstract To preserve freshness and nutritional quality of fruits and vegetables is required large energy expenditure due to most storage techniques require low temperatures, making the product difficult to transport and store. Purpose: To reduce energy expenditure, dehydration processes are being improving by pretreatments and changing frozen stage. Method: Alkaline emulsion pretreatment was introduced to freeze-drying method to reduce the drying time of grapes and obtain significant energy savings. Results: Dehydration process for untreated fresh grape samples was 22 hours, using industrial freeze-drying equipment. It was obtained a high quality product with range 3 % to 7% of final humidity, without losing natural characteristics and organoleptic properties of the grapes. Conclusions: it was found by modifying standard equipment frozen method, using dry ice (CO2) and applied coconut oil alkaline emulsion pretreatment, a 54% energy saving. Even more the dehydration process decreased the microbial load in the fruit. A product with low number of microorganisms may be consumed by patients with low defenses as cereals, nutritional bars, salads, yogurts, etc. Finally, if all enterprises involved in this field take into account these findings and improve constantly their process they will stop emitting several kg of CO2 into the atmosphere.

摘要：维持果蔬的新鲜度与营养品质需要消耗大量能源，原因在于多数存储技术需依赖低温环境，这使得产品的运输与存储难度大幅提升。研究目的：为降低能源消耗，目前通过预处理手段与优化冷冻阶段工艺对脱水过程进行改进。研究方法：将碱性乳液（alkaline emulsion）预处理应用于冷冻干燥（freeze-drying）工艺，以缩短葡萄的干燥时长并实现显著的节能效果。研究结果：采用工业冷冻干燥设备对未预处理的新鲜葡萄样品进行脱水时，耗时为22小时。本工艺可得到最终湿度范围为3%~7%的高品质产品，且未损失葡萄的天然特性与感官品质。研究结论：通过改进标准冷冻干燥设备工艺，结合干冰（CO₂）与椰子油碱性乳液预处理，可实现54%的能源节约。此外，该脱水工艺可降低果蔬中的微生物负荷。微生物含量较低的产品可适用于免疫力低下人群食用，例如搭配谷物、营养棒、沙拉、酸奶等。最后，若该领域内所有相关企业均能参考本研究结论并持续优化其生产工艺，将可停止向大气中排放数千克的二氧化碳。