Vegetables and fruits are rich in vitamins, dietary fiber, mineral elements and a variety of physiological activity of the ingredients, these ingredients in the daily staple food (such as rice, flour) and meat, eggs, milk and other foods do not contain or content is very low The If you do not eat vegetables and fruits for a long time, the body is not enough to maintain normal health. However, a variety of processing means will make the fruits and vegetables in the nutrients caused by varying degrees of loss. High temperature, high pressure and oxidation are the main causes of nutrient damage during processing.Vacuum frying technology, which began in the late 1960s and early 1970s, solves this problem by combining the vacuum technology with fried dewatering, combining heat and low temperature Oil for the heat transfer medium, so that fruit and vegetable tissue within the rapid evaporation of water and dry, thus forming a loose porous structure, called fruit and vegetable crisp. This technology can be better to retain the nutritional content of fruits and vegetables and natural color and flavor, so by the people welcome. In this paper, several common fruits and vegetables in the market as raw materials, the use of vacuum frying technology processing fruit and vegetable crisp, and atmospheric frying nutrient composition comparison.
1 Materials and methods
1.1 Test material
Sugar (Jiangsu Xinyi maltose plant); palm oil (Shanghai Kerry Grain and Oil Industry Co., Ltd.).
1.2 Major instruments and equipment
TR-21-type slicer, TZCA-25 vacuum frying oil removal unit (Qinhuangdao Tonghai Technology Development Co., Ltd.), 1OOL sandwich pot (Wenzhou Light Industry Machinery Factory), assembled activities cold storage, CG250 vacuum degassing tank (Changshu Pharmaceutical Machinery Plant), LSS0.1-0.4-Y Steam Boiler (Yangzhou Sida Boiler Factory).
1.3 Test methods
1.3.1 Process flow
Vacuum frying: raw materials → cleaning peeled → sliced ??→ color → cleaning → bleaching → freezing → thawing, impregnation → vacuum frying, oil removal → sorting test → finished product.
Atmospheric frying: raw materials → cleaning peeled → sliced ??→ color → cleaning → bleaching → freezing → thawing, impregnating → atmospheric pressure frying → atmospheric pressure oil removal → sorting test → finished product.
Vacuum frying with a table vacuum of 0.098MPa, frying temperature of 88 ℃ process parameters, to the end of the same vacuum in the same degassing (built-in) 5min (speed 500r / min); atmospheric frying with frying temperature 160 ℃, 2-5min, and then de-oil 5min (external). Atmospheric fried only sweet potato raw materials for comparison test.1.3.2 Determination of nutrients
Moisture: measured in accordance with the method of NY / T4-1982; mineral elements (potassium, phosphorus, iron, calcium): according to the method of NY / T3-1982; Selenium: measured according to GB / T5009.93-2003 method; carotenoids, vitamin C, dietary fiber: according to GB / T5009-2003 the corresponding method of determination.
2 Results and Analysis
Comparison of Nutritional Components between Different Fruits and Vegetables
2.1.1 protein, dietary fiber, carotenoids and vitamin C
From Table 1 (slightly) to see that several common fruit and vegetable crisp film between the protein content of potato chips (6.16g / lOOg), apple chips the lowest (1.35g / lOOg), the remaining difference is not; Fiber to purple heart sweet potato chips the highest, 28.8g / lOOg, is the lowest content of pumpkin chips 5.6 times, carotenoids between the great differences, including red sweet potato chips and carrots crisp film the highest content, respectively 21.3 mg / lOOg and 19.6mg / lOOg, potato chips are about 30 times, is pumpkin, bitter gourd, apple 4-7 times. Vitamin C with potato chips and red sweet potato chips the highest content, respectively, 26.2mg / lOOg and 25.8mg / lOOg, is the lowest content (carrot chips) about 5.5 times, while the pumpkin, bitter gourd, apple difference between the small The In general, red sweet potato chips in the dietary fiber, carotenoids and vitamin C and other three content are high, is a higher nutritional value of leisure food.
2.1.2 trace elements
The contents of potassium, calcium and phosphorus in several kinds of common fruits and vegetables were 173.15,143.6 and 68.36mg / lOOg respectively, while the contents of iron and selenium were lower, averaging 1.877mg / lOOg and 2.495 g / lOOg. From the coefficient of variation, potassium (74.71%)> calcium (43.39%)> phosphorus (41.90%)> iron (29.00%)> selenium (16.67%). Potassium content of potato chips to the highest, 387.0mg / lOOg, is bitter gourd 31 times; calcium content to bitter gourd highest, 258.2mg / lOOg, potato chips are 4.5 times; phosphorus content of potato, purple potato The content of crisp chips is 3.5 times higher than that of bitter gourd. The coefficient of variation of iron and selenium is relatively small and the content is relatively stable.
2.2 Vacuum frying and atmospheric frying on the nutrient composition of fruits and vegetables
It can be seen from the figure that the different processing methods have obvious effect on the sweet potato nutrition. Atmospheric pressure under the conditions of fried, most of the nutrient content was significantly lower than the vacuum low temperature fried. Under the conditions of vacuum and low temperature frying, the protein content of sweet potato chips was 3.75mg / 100g, which was 1.16 times of atmospheric pressure frying; the content of carotenoids was 21.3mg / lOOg, which was 1.34 times of atmospheric pressure frying; C content of up to 26.2mg / lOOg, is the atmospheric pressure fry 2.7 times; In addition, the vacuum under low temperature frying conditions, calcium, iron, phosphorus, potassium and other trace elements in the loss of ore is also significantly lower than atmospheric fry Processing. At the same time, the total amount of crude fat in vacuum and low-temperature fried products is much lower than that of atmospheric frying. The sweet fat content of sweet potato chips is 23.07g, only 36.1% of atmospheric frying. Therefore, both from the nutritional loss, or oil content situation, the vacuum fried fruit and vegetable crisp is a high-nutrition, low-fat products.
Nutritional loss in the process of fruit and vegetable processing has always been the focus of attention. Vacuum frying is carried out under the condition of high vacuum degree (gauge pressure vacuum 0.098MPa) and low temperature (≤85 ℃), and the nutrient damage of fruit and vegetable is obviously lower than that of atmospheric frying. From the results of this study, it can be seen that the content of most nutrients in the finished product under vacuum frying condition is obviously higher than that of the latter, especially the content of vitamin C, the content of sweet potato chips is 25.8mg, Is the atmospheric frying 2.7 times, while the fresh sweet potato in the vitamin C content is generally 21.5mg / 100g (Su Zhe Henan Wan average), converted into dry base content of about 71.7mg, according to this calculation, sweet potato crisp Vitamin C preservation rate of about 36%, more than l / 3, while the ordinary sweet potatoes in the dry vitamin C content of zero. Vitamin C is a very important nutrient for the human body, and the general processing of hot processing is very easy to lose, so the use of vacuum frying technology is an effective means of preserving vitamin C. In addition, the protein, carotenoids and calcium, iron, phosphorus, potassium and other trace elements of the degree of loss is also significantly lower than atmospheric fry.
Moreover, the technology as a result of the realization of the vacuum frying and vacuum de-oil integration, the product's oil content is also much lower than atmospheric frying. The results showed that the crude fat content per 100g of vacuum fried sweet potato chips was only 23.07g, only 36.1% of atmospheric frying, which significantly reduced the oil content of finished products and reduced the high oil content of ordinary fried potato chips And may bring adverse effects on human health (such as obesity, dyslipidemia and hyperglycemia), and the shelf life of the product from the ordinary fried potato chips extended to a few months to l2 months. Of course, the vacuum low-temperature frying technology on the product appearance of color, crisp and flavor and so on also has a significant change.