Grape is a kind of fruit with very high nutritional value, which contains a lot of vitamins and trace elements that are beneficial to the human body. Raisins are the dried fruits of grapes. High-quality raisins do not crystallize, do not sour, and taste deliciously sweet. The water content in raisins is only 15%-25%, and the fructose content is as high as 60%. Raisins can be eaten directly or placed in a pastry as a garnish.
The traditional drying method is to uses sunlight, but this method will cause problems such as sour raisins, poor color, uneven drying, and easy release of sugar. So how do dry the grapes so that the grapes do not crystallize or sour during the drying process? First of all, make preparations before drying. The grasp dryer must have excellent heating and heat preservation performance and corresponding ventilation and dehumidification equipment. At the same time, the drying process also needs good sanitary conditions to ensure the quality of the product. Our air energy heat pump intelligent fruit dryer can precisely control the temperature and humidity required for drying to produce high-quality raisins. It also has small energy consumption and a high energy conversion rate.
The introduction of the dried grasps
Grapes contain a lot of sugar, mainly glucose, with a sugar content of about 8%-10%. Among the more sugars contained in grapes, most of them are glucose, which is easily directly absorbed by the human body. Therefore, grapes become an ideal fruit for people with weak digestion ability. When the human body has low blood sugar, if you drink grape juice in time, the symptoms can be relieved quickly.
After drying, the weight of the grapes is greatly reduced, and the volume is significantly reduced, which is convenient for transportation and can be stored for a long time without deterioration. Its nutrient-rich and convenient edible characteristics make it popular among prospectors, sailors, and tourists. Raisins contain more flavonoids, which can play an anti-oxidant effect, so eating more can achieve a beauty effect. In addition, raisins can also help digestion and lower blood lipids.
The process of grasp drying
- Raw material selection: Try to select seedless grape varieties with high pulp content, good color, low enzyme browning, suitable maturity, thin skin, soft flesh, and sugar content of more than 20%.
- Pretreatment of raw materials: The selected grapes need to be washed and decontaminated. Generally, we use the 1.5%-4.0% sodium hydroxide for easy washing to remove wax and harmful microorganisms attached to the peel. At the same time, small cracks will appear in the peel to facilitate the evaporation of water and promote drying.
- Drying: The sugar content in grapes is high, which is easy to lock in moisture. The drying process is divided into four steps.
- Put the grapes in the grasp drying room, the initial temperature is set between 40-50℃, it lasts two hours. At this stage, the grape skin moisture slowly evaporates.
- In the mid-term, increase the temperature to 65℃ and set the humidity to 15%. This stage lasts for 8 hours, and the grape dehydration rate at this stage is about 80%.
- At this stage, most of the total moisture of the grapes has been discharged. Set the temperature to 40℃. While increasing the temperature difference, the moisture removal will be further strengthened for four hours.
- Finally, reset the temperature to between 40-50℃, and dry slowly for two hours. At this time, the moisture content of the grapes will be less than 12%.
Tips about the grasp drying
- The water content of grapes is relatively large. Generally speaking, every 4 kg of grapes can get 1 kg of raisins after drying, and the dehydration rate reaches about 70%.
- There are two ways to dry grapes. One is to simply trim, clean, and drain the whole bunch of grapes, then hang them directly on a cart for drying. After drying, subtract it from the grape bunches, cleaned, and re-baked. Another method is to directly put the pruned grapes in a tray for drying. This method is faster but has a higher breakage rate.
- Adequate cooling is required after drying. The dried grapes must be ventilated and dissipated, until completely cool before stacking together. The grapes contain a lot of sugar, the sugar is easy to ferment and deteriorate under the action of heat, and the original pectin in the grapes will also decompose pectin and pectic acid. This will make the grapes all bond together, and will also change the sugar in the grapes, and produce sour filaments, which will destroy the grapes. Therefore, after drying, it must be completely cooled before storage.
- High-quality raisins require that the raisins do not change color and have soft flesh. The raisins are dry in the hand, no juice oozes out, and the granules are quickly dispersed and the dryness is suitable. The taste is neither sour nor astringent, but sweet and mellow.
Applications of the grasp drying machine
Our grasp drying machine is also suitable for fruits, fungi, Chinese medicinal materials, seafood, crops, and some chemical products. It also can be customized according to the user’s demands for different products.