Freeze Dried Fruit Process

Today, let's talk about the information on the research and development of new technologies for energy saving and consumption reduction of fruit freeze dryers. The following will start with fruit freeze drying.

1. Pretreatment and prefreezing technology of freeze dryer

Pre-treatment technologies such as blanching and color protection can not only improve the quality of products, prolong the shelf life, but also speed up the drying rate and reduce energy consumption while removing part of the water and changing the tissue morphology. For example, the effect of high-voltage pulsed electric field (Pulsed electric field, PEF) on apples has confirmed that PEF treatment can improve the rehydration and porosity, and accelerate the sublimation drying rate. In addition, PEF has the characteristics of fast and uniform transfer, small temperature rise, and short processing time, which is especially suitable for the treatment of some heat-sensitive fruits, and has broad application prospects in the field of FD. Ultrasonic can improve the water loss rate and solids yield in the process of fruit infiltration, shorten the drying time, and improve product quality through the functions of cavitation, microporous channels and sponge structure.

According to the different physical properties of the fruit, choosing one or more suitable pretreatment methods can effectively speed up the drying rate, improve the product quality, and meet the market demand to a greater extent. The freezing rate and subcooling degree of lyophilizer pre-freezing treatment can affect the size and distribution of ice crystals, which in turn affects the subsequent sublimation drying process.

The ice crystal particles formed in the pre-freezing process are large and small in number, which can improve the sublimation and drying rate. However, as the main cause of cell damage, the larger the ice crystal particles and the more the number, the more serious the damage to the cell structure, and the worse the various physical and chemical sensory qualities. Difference. Therefore, it is extremely important to control the suitable freezing rate and adjust the ice crystal nucleation with low consumption freeze dryer fruit, so that it can meet the requirements of quality and energy consumption at the same time.

2. New technology of combined drying of freeze dryer

Combined drying is a composite drying technology that combines the advantages of various drying methods and complements the advantages of two or more drying methods. It can make up for the shortcomings of poor product quality and low drying efficiency in a single drying method. It has the characteristics of retaining the original sensory quality and color of the material to a greater extent.

Compared with other combined drying technologies, the freeze dryer combined drying technology combines the advantages of FD high quality and other drying low energy consumption by using low consumption freeze dryer fruit, and has obvious advantages in improving energy efficiency and product quality, the application prospect is broad. At present, the common freezing combined drying technologies include hot air-freezing, microwave-freezing and infrared-freezing and other combined drying technologies.

1. Freeze-hot air combined drying: For the combined drying technology of AD and FD, the currently recognized practice plan at home and abroad is to freeze-dry to a certain moisture content first, and then perform hot-air drying after the material skeleton is formed, eliminating the need for the FD analysis section. This saves drying time, and at the same time, the product will not be severely deformed and discolored. The combined application development of AD and FD technology is relatively mature. Because of its low energy consumption, it has been widely used in practical production, but the product quality is still poor. How to further improve the product quality of hot air freezing combined drying is the focus of future research.

2. Microwave-freeze combined drying: The combined use of MD and FD technology is one of the potential research directions in fruit drying today. Microwave-freeze combined drying has obvious advantages. Its product nutrient retention rate is much higher than that of single microwave drying, and the drying time is much lower than that of single FD. However, there are still many problems to be solved in practical applications. Developed in the laboratory, it has not been used in industry until now. With the development of microwave hardware, the cost of joint equipment has gradually decreased, and it has more and more industrial value. At present, it has been applied to industries such as biopharmaceuticals and convenience foods, and it is the research direction of the future industrialized production of dehydrated fruits.

3. Infrared-freeze combined drying: Infrared-freeze combined drying is an emerging fruit drying technology in recent years, and it is still in the research and development stage. In the drying process, infrared radiation can directly penetrate the material and convert it into molecular vibration to generate heat, thus reducing the loss of heat in the air and effectively reducing drying energy consumption.

4. Infrared-vacuum freezing combined drying: Although it started late, there is less research, and there is limited information on comprehensive aspects such as drying kinetics, energy consumption and product quality, it is undeniable that infrared radiation has an effective role in reducing FD energy consumption; in the future, it is necessary to develop a more advanced test device and establish a drying kinetic model to achieve in-depth.

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