Vacuum low-temperature deep-frying technology is to make the water in food materials vaporize rapidly under reduced pressure (vacuum), to complete the dehydration process rapidly in a short time, and to realize the dehydration process of food under the condition of low temperature (90℃).

As a new technology for rapid dehydration of food, low-temperature deep-frying technology can play a role in improving the flavor of food. The pretreatment of food materials such as bleaching, color protection and impregnation before low-temperature deep-frying can maximize the maintenance of the original state of food materials, increase the solids content of food after deep-frying, and reduce the oil content of vacuum low-temperature deep-fried food. From the academic point of view, vacuum deep-frying technology is actually a drying and dewatering process of food materials with low-temperature oil as the medium.

Advantages of vacuum low-temperature deep-frying technology

1.1 Lower frying temperature, less nutritional loss of food materials

In daily life, atmospheric pressure deep-frying deep oil temperature is generally above 160 ℃, and can even reach 230 ℃, deep-frying food at such a high temperature will cause the loss of nutrients in food.

However, vacuum low-temperature deep-frying technology can control the temperature of oil used for deep-frying to maintain at 90~100℃, which greatly reduces the damage of high temperature to the nutrients in the food, so that the effective nutrients in the food materials can be retained better.

1.2 Short dehydration time

Under the state of vacuum and low temperature, the dehydration speed of food materials is fast. Since the oil temperature of vacuum low-temperature deep-frying technology is low, it can keep the original color and character of food materials to the maximum extent.

1.3 Retain the aroma and flavor of food materials themselves

Food materials in the aroma and flavor components are mostly water-soluble components, the use of vacuum low-temperature deep-frying technology, food materials in a sealed state and low-temperature conditions and slow heating, in the process of low-temperature oil bath is very little dissolved, and with the continuous reduction of water in the heating process in the food materials, food materials in the aroma and flavor components to be further concentrated.

1.4 Has a certain puffing effect

Food material cell tissue interstitial water in the low-pressure state of rapid vaporization and expansion, volume increase, from the gap in the punch out of the food material has a certain puffing effect.

Food materials in the vacuum low-temperature deep-frying before the -25 ℃ environment in the freezing process, so that the moisture between the cellular organization of the formation of ice crystals, the destruction of the cell structure, the effect is better.

1.5 Small oil consumption, not easy to oxidize

Vacuum low-temperature deep-frying technology of low oil temperature, and in a completely sealed state for deep-frying, the oil surface and air contact area is small, resulting in deep-frying oil is not easy to oxidize, the acid value of fats and oils and peroxide value of the slow rise, not easy to rot.

Vacuum low-temperature deep-frying technology can effectively control the oil content of food materials below 20%, compared with the oil content of normal temperature and normal pressure deep-frying food in 40% to 50%, vacuum low-temperature deep-frying technology, oil consumption is smaller.

Vacuum low-temperature frying technology

Application in the field of food processing

2.1 Vacuum low-temperature deep-frying technology in the field of fruit and vegetable processing applications

Wang Yu in the vacuum low-temperature deep-frying process of dehydrated garlic slices in the study of deep-frying temperature, pre-drying time and deep-frying time for the examination of factors to the oil content of garlic slices and sensory scores as an indicator, to determine the optimal vacuum low-temperature deep-frying of garlic slices of the optimal process parameters for the garlic slices sliced thickness of about 2mm, in the mass fraction of 15% maltodextrin solution macerated at room temperature under normal pressure for 30min, in the mass fraction 0.75% sodium alginate solution Impregnation for 30 min, hot air pre-drying at 60℃ for 2h, vacuum degree 0.08~0.09 MPa, frying temperature 90~100℃, frying time 10~15min, rotary degreasing for 4min, rotational speed 350r/min, oil content of dehydrated garlic slices was 10.27%.

He Jianjun et al. in the vacuum low-temperature deep-frying lotus root slices process research to get the best process for the raw material lotus root after screening, peeling and cleaning, slicing, rinsing, color protection, rinsing and blanching and other pre-treatment, impregnated with seasoning impregnating solution containing 6% maltodextrin, 2% salt, 0.5% monosodium glutamate for 70 min, drained and pre-dried for 40 min, deep-fried at 100 ℃ in a vacuum environment 40 min, and finally degreased for 6min The finished products were packaged.

Li Jiang and others in the vacuum low temperature deep-frying jujube production process in the vacuum low temperature deep-frying jujube best process for deep-frying temperature 90~105 ℃, deep-frying time 30min, vacuum degree 0.096 MPa, rotary de-oil speed 120~150 r/min, de-oil time 3min.

2.2 Application of vacuum low-temperature deep-frying technology in edible mushroom processing

Wang Min studied the vacuum low-temperature dehydration process of apricot mushroom to get the optimal process of vacuum low-temperature deep-frying apricot mushroom crisps with a thickness of 2mm apricot mushroom slices scalded and bleached at 80℃ for 90s, and then impregnated with the material-liquid ratio of 1:15 (g:mL), the ultrasonic-assisted impregnation of maltodextrin with a mass fraction of 15%, and then pre-dried with hot air for 20min at 60℃, with a deep-frying temperature of 80~90℃, a vacuum degree of 0.08~0.09MPa, and a deep-frying time of 3min. 0.09 MPa, frying time 10 min, rotary degreasing speed 350 r/min, degreasing time 10 min, the final oil content of the product was 30.43%.

Andong et al. determined the optimal vacuum low-temperature deep-frying process parameters of mushroom crisps in low-temperature vacuum deep-frying process research as the proportion of impregnating liquid 30% maltose solution + 15% maltodextrin + 1% salt, vacuum deep-frying temperature 100 ℃, deep-frying time 30min.