(1) Selection of raw materials
Choose apples with tight organization, good flavor, high acidity and white flesh. It is required that the fruit is fresh and full, the maturity is about 80%, the flavor is normal, and there is no deformity, mildew, frostbite, insect pests and mechanical damage. According to the classification of fruit size and maturity, the transverse diameter of the fruit is required to be above 60 mm, and the fruit is peeled by machinery or peeling agent after washing, and then cut into petals longitudinally, and the seed nest and pedicel are dug out; The excavation surface shall be complete and smooth; Trim scars and residual skin, rinse 1~2 times with clear water, and immediately immerse in 2% citric acid solution or 2% salt solution to protect color.
(2) Classification
Apples are divided into three grades according to the transverse diameter: 60~70mm, 67~75mm and above 75mm. Individual varieties may be below 50 mm, and the grading of fruit and vegetable raw materials includes grading according to the size, quality and quality of raw materials. The purpose of grading by size is to facilitate the subsequent process treatment, achieve uniform and consistent processed products and improve product quality. For example, fruits of the same size and shape can be peeled mechanically, and fruits and vegetables of the same maturity can be blanched at the same time. Grading raw materials according to quality can unify the quality of finished products and ensure that the specified product quality requirements are met. Special attention should be paid to the classification of vegetable raw materials stored in cans. The classification of fruits mainly adopts screening method. According to the size of the fruit, the grading screen, grading disk, grading belt and grading roller with different apertures are selected.
(3) Cleaning
Wash with clean water. Cleaning can remove dust, sediment and a large number of microorganisms attached to the surface of fruits. Ensure that the products are clean and hygienic, especially the raw materials sprayed with pesticides, and pay more attention to washing them to remove the phytotoxicity. Washing water, except hard water for making candied fruit and preserved fruit, is soft water for other processing raw materials. The water temperature is generally normal temperature. Sometimes in order to increase the washing effect, hot water can be used, but it is not suitable for soft and juicy fruits with high maturity. Soak in water before washing, and the dirt will be washed off more easily. If necessary, soak in hot water. Raw materials with toxic substances left on the peel must also be cleaned with chemicals. Commonly used chemicals are 0.5%~ 1.5% hydrochloric acid solution or 0. 1% potassium permanganate solution or 600× 10-6 bleaching powder. Soak for a few minutes at room temperature, and then wash away the chemicals with clear water. When washing, let the water flow or fruit vibrate and rub to improve the washing effect.
According to the degree of pollution, compression and friction resistance and the surface state of each fruit, the cleaning method is different. Commonly used washing machines are: washing sink, which is relatively simple and suitable for washing all kinds of fruits and vegetables, but it can't be continuous, with low efficiency and large water consumption. Drum washing machine is suitable for raw materials with hard texture and not afraid of mechanical damage on the surface. Spray-type and pneumatic washing machines have little damage to fruits and good effects, and are suitable for washing soft and juicy fruits.
(4) Peeling
Peel by hand or peeler, and the thickness of peeled peel is generally less than 2 mm to reduce the consumption of raw materials. Because apple pulp is easy to change color, it should be treated immediately after peeling.
(5) color protection
After peeling the apple, it should be put into 1%~2% salt water or 0. 1%~0.2% citric acid solution to prevent the apple from browning.
(6) dicing and coring
Cut in half longitudinally with a stainless steel fruit knife. Large fruits can be cut into four pieces with smooth sections. The cut fruit pieces were immediately immersed in 1%~2% salt water for color protection. The method of cutting and crushing raw materials is different according to the nature, shape and processing requirements of raw materials, with less manual work and more machinery. Remove the core, stem and calyx with a knife, remove the residual skin, and soak in 1%~2% salt water in time to protect the color.
(7) degassing and blanching
Apple tissue contains about 25% gas, which can increase the bulk density of the product after degassing. Steam and sugar liquid can easily enter the fruit tissue during blanching and sugar infiltration. Degassing can be carried out under the vacuum of 94.6~98.6kPa, and the degassing time is about 65438±00min. After degassing, steam can be directly introduced into the vacuum tank. On the one hand, it can break the vacuum and blanch at the same time. When the steam temperature is 1 160℃, the blanching time is about 14~45s. After blanching, condensed steam is filled into the fruit tissue, and the fruit slices are translucent. In this process, the loss of fruit chips is very small, and its quality loss is generally around 1.4%. The loss of sugar and acid accounts for about 1%.
can
(1) Prepare empty cans
Empty cans should be cleaned and disinfected before use to remove dirt, microorganisms and grease. Empty tinplate cans can be washed with hot water first, then disinfected with clean boiling water for 30~60s, and then dumped for later use. The tank cap is also treated in the same way. Empty cans after cleaning and disinfection should be used in time, and should not be put on hold for a long time to avoid rust and re-pollution. The glass jar container is often scrubbed by the bottle washer with a brush, then sprayed with clean water or high-pressure water several times, and drained upside down for later use.
(2) Configuration of bath solution
The concentration of sugar solution depends on the kind, variety, maturity, pulp content and product quality standard of fruit. Generally speaking, the sugar content of canned fruit in syrup produced in China is 14%~ 18%. The calculation method of liquid concentration in storage tank during filling is as follows:
y =(W3Z-w 1X)/w2× 100%
Where: Y- concentration of sugar solution to be prepared,%;
W 1- weight of pulp per can, g;
W2—— weight of sugar solution injected into each tank, g;
W3—— net weight of each can, g;
X refers to the content of soluble solids in the pulp when canning,%;
Z—— concentration of sugar solution required when opening cans,%.
The concentration of sugar solution can be prepared according to the calculation results, so it can be used directly. However, it is often prepared into high concentration sugar solution and diluted when used. After the sugar solution is prepared, it must be boiled and filtered before use. When boiling, keep the temperature at about 60℃, skim the impurities floating on the liquid surface before boiling.
(3) Sugar injection
That is to say, the processed raw materials are first put into an empty sterilization tank, and then an appropriate amount of tank liquid is injected, and the tank liquid temperature is required to be kept at about 800℃ to improve the initial temperature of the tank. When filling cans, it is required to be timely, sufficient in quantity, uniform in shape and with top clearance. And the increase of the number of microorganisms can be avoided. Enough means that the net weight of canned food meets the requirements, and the weight of solid matter is 55%~60% of the net weight. Shape means that the size, shape and color of fruit pieces in the same can should be basically the same, especially plastic cans. Top clearance refers to keeping a certain distance between the surface of the food in the can and the lid of the can after canning, generally 4~8 cm. Excessive top clearance will lead to insufficient exhaust, more residual air, corrosion of the tank and discoloration of food on the surface; The gap at the top is too small, which expands when heated during sterilization, resulting in the bulge of the bottom cover, poor sealing and physical expansion after cooling.
Exhaust seal
The apples should be vented and sealed after being canned and filled with liquid. The main purpose of exhaust is to exhaust the residual air in the headspace and food tissues of cans as much as possible, so that a certain degree of vacuum can be formed after sealing, so as to prevent the cans from deteriorating and prolong the shelf life. Exhaust methods mainly include hot exhaust, vacuum exhaust and steam injection exhaust.
disinfect
Canned food should be sterilized when sealed. Canned fruit is an acidic food with low PH value. Generally disinfected with boiling water. The sterilization time is related to the original temperature of materials and the size of cans, and the central temperature of cans should reach 82~850C C.
The simplest method is to sterilize with boiling water in a jacketed pot. Normal pressure continuous sterilization equipment can also be used.
cool
After sterilization, the canned food should be cooled immediately, usually to 36 ~ 420℃. If the temperature is too high, the contents will be too soft, the color will become worse and the sugar solution will be turbid. If it is cooled below 30C, the moisture on the surface of the can will not easily evaporate and dry. The water used for cooling shall meet the national standards and shall not pollute the products or corrode the containers.
According to the different cooling positions, the cooling methods can be divided into external cooling and internal cooling. External cooling is often used for atmospheric sterilization, and internal cooling is often used for pressurized sterilization of horizontal sterilizers. According to the cooling medium, there are air cooling and water cooling, and the water cooling effect is the best. In order to speed up the cooling speed during water cooling, it is generally the most common way to soak in running water.