Path to development: Using microwaves and vacuum to dry fruits

What is microwave vacuum drying? In simple terms, microwave vacuum drying is a technology that combines \"microwave drying\" and \"vacuum drying\". To understand what microwave vacuum drying is, one must first understand what microwave drying is and what vacuum drying is. Microwave drying technology originated in the 1940s, while it was not adopted in China until the 1970s. Microwave drying involves using electromagnetic waves to transfer energy into the interior of an object, converting microwave radiation energy into kinetic energy of molecules in orderly motion. Through collisions and friction between these molecules, the internal energy of the object increases, its temperature rises, and a large number of molecules escape, thereby achieving the purpose of drying. Simply put, electromagnetic waves cause molecules to move. It works on a principle similar to that of a microwave oven. A microwave oven uses microwave radiation to heat food, causing the polar molecules within it (such as water) to move and rub against each other, thereby generating heat. Unlike traditional drying methods, which first dry the surface before gradually drying the inner layers, microwave drying dries both the outer and inner parts simultaneously, thus avoiding the drawback of the surface becoming easily charred in conventional drying processes. We can understand this by thinking about the differences between a microwave oven and an oven. However, microwave drying also has some limitations, such as high costs for the equipment, a tendency to overheat, and a limited range of applications. Vacuum drying is a drying method in which the material is placed under negative pressure; either by applying appropriate heat to reach the boiling point under that pressure, or by cooling the material to cause it to solidify and then drying it at its melting point. Generally, the vacuum-packed foods we see are produced by removing air and using reduced pressure for drying; this is a common method used in the market today to extend the shelf life of food. Vacuum isolates the food from air, preventing oxidation and spoilage, and it provides a good drying effect. However, it has one drawback: the drying speed is slow and the drying time is long, which leads to significant loss of the fruit’s nutritional components. It is unable to preserve the fruit’s color, flavor, and nutritional values effectively.

The new fruit drying technology resulting from integration combines microwave drying with microwave vacuum drying, giving rise to the microwave vacuum drying technique. Microwave vacuum drying technology uses microwave radiation as a heating source, and then applies heat under vacuum conditions to dehydrate fruits. What are the advantages of combining these two methods? Microwave drying heats the fruit quickly and evenly. In a vacuum environment, the boiling point of water decreases, which allows the operating temperature to be reduced; this prevents the destruction of nutrients due to high temperatures, thereby preserving the flavor and nutritional values of the fruit to a large extent.

Dried fruits probably give most people the impression of being sweet, extremely sweet. That’s right, because this is a process of concentration. However, compared to preserved fruits, candied fruits, and fruit chips, dried fruits are the type of fruit product with the highest nutritional value. This drying process concentrates the sugars, proteins, fats, and various minerals in fruits, as well as dietary fiber and some heat-resistant antioxidants. Vitamins are also concentrated, although nutrients that are more sensitive such as vitamin C and vitamin B1 decrease in amount. Among them, vacuum freeze-drying involves no heating and minimizes oxidation, thereby allowing the preservation of most vitamins. During drying, due to exposure to air and sunlight, almost all of the vitamin C is lost. The vitamin loss for infrared and microwave drying methods is somewhere between these two. Nutrient loss is minimal under microwave vacuum drying, which is why it has become a focus of research in various countries in recent years. It can also be said that microwave vacuum drying technology is currently the best drying method for preserving the original flavor of fruits. Especially in the production process of dried fruits, microwave vacuum drying technology is highly suitable. Of course, there is also a long-standing problem with the promotion of this technology: the equipment investment is too high, making it difficult for ordinary fruit processing enterprises to afford it.

Thanks for sharing; the original poster, please post some dried kiwifruit

I don’t quite understand what is meant by the high cost of equipment investment – what type of equipment is it exactly? I’m looking for some information, bro.

The dried kiwifruit, dried mango, and dried bananas that are common here taste quite good.

Genuine dried fruits must have a high nutritional value, but it seems that many of those available on the market contain sugar; they’re too sweet, and eating them probably isn’t very healthy