Raisins are fresh grapes that have been dried and hydrated. Good quality raisins are full and elastic in shape and have a sticky sweet taste. Also, good quality raisins have non-crystallizing and non-acidic fructose. So how to make good quality raisins in the process of drying grapes? Grapes are rich in fiber and sugar. And the raisin drying process is also the process of ripening grapes. This is the process of converting polysaccharides into monosaccharides by the action of biological enzymes, while preserving as much as possible the original quality of the grapes. This results in a better sweetness of the raisins.
兩種不同的葡萄乾製作方式
The optimal temperature for the conversion of the internal sugars into simple sugars during the drying process is 55-60 degrees. There are two ways of processing raisins: natural drying and using a grape drying machine. The natural drying time is long and the temperature cannot be controlled, which does not meet the needs of large-scale production. The 葡萄乾機, on the other hand, can precisely control the drying temperature and humidity in the drying process. On the other hand, the dryer has the advantages of low operating cost and high efficiency. It is an indispensable machine necessary for modern production.
葡萄乾機的產品特點
葡萄乾機是由風能熱泵烘乾機、對流送風系統、溫濕度智慧控制系統、乾燥室等組成的專業烘乾設備。它具有良好的加熱與保溫、通風及水分散發設備，同時具有非常良好的衛生條件。乾燥機主機從空氣中吸取熱量，經壓縮機形成熱風，經對流風扇均勻吹入乾燥室。乾燥機內部的感測器可以記錄溫度和濕度，之後再控製乾燥溫度與乾燥時間。
選擇高品質葡萄以製作葡萄乾
我們需要選擇顏色鮮艷、皮薄肉厚、成熟度適中、糖含量高於20百分比的葡萄。然後清洗它們，放入葡萄乾烘乾盤中。只有高品質的葡萄才能用於獲得高品質的葡萄乾。
葡萄乾機的溫度控制
- 起始溫度設置在40-50攝氏度，持續2小時。本操作的目的是促進葡萄皮的水分蒸發。
- 中期大規模脫水：將溫度提高至55攝氏度，持續10小時。此時葡萄的脫水速率約為70%。
- 深度乾燥：將溫度升至60攝氏度。濕度設為55%，持續10小時。
- 最後，溫度控制在55攝氏度，烘焙時間為5小時。此時，葡萄的水分含量低於12%。
此時，葡萄乾沒有變色，果肉柔軟。葡萄已經乾燥，沒有汁液滲出。當握緊一把葡萄乾並放開時，顆粒會迅速散開。這表示乾燥程度適中。我們可以看到白色葡萄乾外面有少量的糖霜。去除糖霜後，顏色呈水晶綠且透明。紅色葡萄乾也有略微的霜狀外觀。去除霜後，顏色呈半透明的紫色。水分含量少於15%。
註釋
葡萄含有大量水分，通常4磅葡萄可產1磅葡萄乾。葡萄的脫水率約為70%。由於葡萄外皮容易破裂，裝載到葡萄乾燒盤時需輕放並小心操作。不要過度擠壓。