Freeze Dryer For Plant-Based Foods

Freeze dryer for Plant-based foods

The wide range of freeze-dried fruits that have been reported in the literature includes strawberry, blackberry, guava, pineapple, etc. Fresh fruits containing high moisture levels are difficult to dehydrate by classical drying techniques due to significant damage to their physical attributes, mainly collapse and severe bleeding due to the rupture of skin. Shishehgarha et al. studied the various quality parameters (drying kinetics, color, and volume variation) of sliced and whole strawberries under different FD shelf temperatures (30, 40, 50, 60, and 70℃). The level of shrinkage was found to be independent of FD shelf temperature, where whole and sliced strawberries had an average volume reduction of 8% and 2%, respectively. On the other hand, the risk of collapse was found to increase exponentially once the FD shelf temperature surpassed the glass transition temperature of dried strawberries. 

Shrinkage and collapse of fruits are often encountered during drying, mainly by air-drying techniques. Hawlader et al. compared quality of guava obtained by heat pump dryers (RH = 10%, v = 0.7 m/s, T = 45℃, 8 h), vacuum (vacuum pressure = 15,000 Pa, T = 45℃, 8 h), and freeze-dryers (freezing at −20 ◦C for 24 h, and less than 613.2 Pa vacuum pressure, 10 ◦C shelf temperature, 24 h for freeze-drying).

Porosity, color, rehydration, and vitamin C retention of guava produced by FD were better, resulting in FD guava being the most desirable powder compared to that produced by vacuum and heat pump dryers. FD was able to retain 63% vitamin C, whereas the heat pump dryer retained only 25%. It is often challenging to dehydrate fruits with waxy impermeable skin, as described previously, such as seabuckthorn berries (Hippophae rhamnoides L.), which are delicate fruits containing natural antioxidants, ascorbic acids, carotenoids, and flavonoids. Araya-Farias et al. investigated the effect of hot air drying (HAD) at 1 m/s and 50 ◦C or 60 ◦C, and FD (4 Pa of vacuum, 20℃or 50℃shelf temperature) to obtain dried seabuckthorn pulp. They found that FD retained 93% more carotenoids, 34% more vitamin C, and 11% more phenolics than HAD. Increased drying temperature resulted in an increase in drying kinetics. However, no significant impact of drying temperature on overall nutritional retention was noticed for FD or HAD samples, although a slight decrease was found for particular compounds such as vitamin E for both drying methods while increasing the operating temperature. Between two drying processes, it was reported that drying kinetics were surprisingly faster in FD.

Vegetables are a good source of essential nutrition for the human diet. Dehydration of vegetables is usually done for their long-term consumption. Studies on FD of some vegetables, including asparagus, carrot, pumpkin, and tomato. Nindo et al. studied the drying Foods 2020, 9, 87 8 of 22 of sliced asparagus using FD and other drying methods including tray dryer, reflectance window dryer, and spouted bed dryer. The highest amount of ascorbic acid was retained when samples were dehydrated by FD and refractive window drying. Freeze-dried pumpkin has numerous applications in manufacturing formulated foods such as soups, noodles, bread, and cakes. Several authors have studied the FD of pumpkin to characterize its nutritional and physicochemical properties for the above-mentioned food applications. Guiné et al. reported a decrease in moisture content from 90% to 8% in freeze-dried pumpkin, but FD induced a softening of the pumpkin, as the hardness of the pumpkin decreased from 19.37 N (fresh) to 1.59 N (dried/rehydrated) when the textural properties were analyzed. Also, the change in color was important (total change in color, ∆E = 12). Ciurzy ´ska et al. studied the effect of different pretreatment methods (blanching and osmotic dehydration) on the properties of freeze-dried pumpkin. The long duration of osmotic dehydration caused a decrease in the water content of pumpkin and on water activity of final freeze-dried samples.

Our company specializes in the production of Freeze dryer for Plant-based foods.

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* As soon as we get your inquiry, we will always reply to your email on time and try our best to recommend you the most suitable freeze dryer. Detailed tech-info will also be provided for you.

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After-sale:

* If possible, please do come to our factory and we will teach workers the whole process of freeze drying. The most appropriate time needed for freeze drying will be tested by us.

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