Blueberry, scientific name cranberry, the fruit is blue, delicate flesh, sweet and sour delicious and nutritious, known as the "king of berries," is also listed by the international food and agriculture organization the five human health food. Blueberry abounds in the season of high temperature and rainy, and the harvest time is short. Due to the concentrated picking period, it is easy to accumulate fruits, and fresh fruits are not easy to store. However, the quick-freezing method can prolong the storage period of blueberries.
Advantages of blueberry continuous microwave defroster：
1.The blueberry microwave defroster defrosts quickly.
There were significant differences in defrosting time between different microwave defrosting methods < ultrasonic defrosting < water bath defrosting < defrosting < low temperature defrosting.
Thawing at low temperature and normal temperature uses air to conduct heat transfer with the blueberry surface while thawing at a water bath uses water to conduct heat transfer. However, air's thermal conductivity is much lower than that of water, so the thawing time at normal temperature and low temperature is longer than that of a water bath.
The microwave uses the dielectric properties of materials for thawing; a continuous blueberry microwave thawing machine can make the surface and inside of the frozen blueberries at the same time heating. The frozen blueberries quickly thawed. Microwaves thaw and heat up quickly.
2.Blueberry continuous defroster has the lowest juice flow.
Juice flow rate is one of the important indexes of defrosting quality, which can judge quick-frozen blueberries' moisture retention. The juice loss of quick-frozen blueberries was different with different thawing methods; the microwave's lowest defrosting rate was 0.66%.
Since microwaves have a certain penetrating ability, they can penetrate into the interior, thus achieving simultaneous heating inside and outside. Simultaneously, the internal ice crystals dissolved rapidly in the original position of organelles, and the continuous blueberry microwave defroster made the sample tissues rehydrate rapidly, reducing the juice loss rate during the defrosting process.
The defrosting rate of the water bath and ultrasonic defrosting was 4.71% and 4.64%, respectively.
These two defrosting methods were carried out under a water bath, and the temperature was transferred from the peel to the interior. When the pulp's central temperature reached 4 ℃, the surface of the peel would overheat, which would lead to a high juice flow rate of quick-frozen blueberries.
3.Continuous blueberry microwave defrosting machine keeps fruit firmness well.
The continuous blueberry microwave defrosting machine can maintain skin firmness and keep the flesh firmness. Microwave defrosting is fast and does little harm to cells. Water bath, ultrasonic, and normal temperature defrost because the defrost time is long and the temperature is high, the epidermis is heated for a long time. The damage to the cell is great, resulting in a decrease in hardness.
4.The continuous microwave defroster had little loss of active ingredients in blueberries.
Blueberry anthocyanin has the function of lowering blood lipid and anti-oxidation; its variation has an important influence on the quality.
The anthocyanin content of blueberries by different thawing methods is in order: low-temperature thawing > microwave thawing > ultrasonic thawing > water bath thawing > normal temperature thawing. The content of anthocyanins in blueberries decreased after thawing. Due to the short thawing time of blueberry continuous microwave thawing equipment, the damage to blueberry anthocyanins in quick-frozen blueberries was less, which was only second to thawing at low temperature.
The anthocyanin content in the water bath and normal temperature defrosting decreased significantly, which was due to the long defrosting time and slow rate, and the high temperature caused the content of anthocyanin to decrease. Blueberry fruit is rich in VC, which is an important nutritional index.
Low temperature and microwave thawing had the least damage to VC, with the loss rate of 7.40% and 10.80%, followed by water bath and ultrasonic thawing, with the loss rate of 28.30% and 36.90%, and the worst was at room temperature thawing, with the loss rate of 55.50%.VC is a water-soluble substance with strong thermal sensitivity, so the loss rate of VC content in room temperature thawing, water bath thawing, and ultrasonic thawing is large.
Blueberry continuous microwave defrosting machine
Compared with fresh blueberries, defrosting methods greatly influence the quality and active ingredients of blueberries, and different defrosting methods have different influences on different indexes.
During the thawing process of ultrasonic wave and water bath, the temperature was high, so the fruit hardness characteristics were poor, the juice rate was high, and the content of acid and soluble solid dropped significantly. Due to the long thawing time and high temperature, the active ingredients of fruits decreased the most. Thawing fruits at a low temperature kept the active ingredients best but thawed them for the longest time.
Compared with the above four defrosting methods, blueberry continuous microwave defrosting equipment can defrost fruits, soluble solids, titratable acids, and other foods. Moreover, it maintains the best hardness, the lowest juice loss rate, the shortest thawing time, and the highest quality, which can be used as the suitable quick-frozen blueberry processing method.