Detailed explanation of processing techniques for almonds, dried apricots, and apricot juice

The apricot tree is one of the ancient cultivated tree species in our country and is widely distributed. Apricot fruit is a treasure in every part, containing rich vitamins and mineral elements. Every 100g of flesh contains 10g of sugar, 0.9g of protein, 1.79g of carotene, 0.02mg of thiamine, 0.03mg of riboflavin, 0.6mg of nicotinic acid, and 7mg of vitamin C. Almonds contain about 23% protein, 50%-60% fat, with an oil yield of 45.8%, and are rich in phosphorus, calcium, potassium, iron and other nutritional elements needed by the human body. They are an excellent tonic and an important raw material for the food industry. Apricot fruits processed into almonds, preserved apricots, dried apricots and other foods are very popular in domestic and international markets, with high economic benefits.

1 Processing of almonds

1.1 Process flow

Kernel apricots -> dehulling -> sun-drying of pits -> cracking of pits -> kernel sorting -> finished product.

1.2 Processing key points

1.2.1 Dehulling For apricots used for both kernel and flesh, and kernel apricots where the flesh is retained, after harvesting the pits must be carefully pinched out, keeping the apricot skin intact. For kernel apricots where only the pit is taken, after air-drying, the pits are removed by rolling and tapping with a wooden stick, then the pit and flesh are separated by winnowing and manual sorting of pits.

1.2.2 Sun-drying of pits After dehulling, apricot pits still contain a large amount of moisture, so they must be sun-dried. When sun-drying pits, they should be spread out in a place with ample sunlight and turned intermittently for 5-6 days, until the pit shells are thoroughly dry and the almonds rattle when shaken, at which point they can be collected and cracked to extract the kernels. If the apricot pits are not thoroughly dried, they are neither easy to store nor easy to crack for kernels, so sun-drying apricot pits plays an important role in improving the quality of almonds.

1.2.3 Pit cracking There are 2 methods of pit cracking: manual cracking and machine pressing. At present, the machine pressing method is mostly used in production to obtain almonds, that is, using a dedicated pit-cracking machine to extract kernels, including hand-cranked pit-cracking machines and electric shellers. The hand-cranked pit-cracking machine used in production has a pit-cracking capacity of 200kg/day, and the electric sheller has a pit-cracking capacity of 2000kg/day. A relatively good sheller is the **500-type sheller manufactured by Bayi Agricultural College, which can process 4000kg of apricot pits per day, with a kernel breakage rate of only 7%.

1.1.4 Kernel sorting After cracking kernel apricots, the kernels and shell fragments are mixed together. A winnowing machine or winnowing basket can be used to first sift out part of the shell fragments, and then the almonds are picked out. When sorting kernels, damaged kernels, bad kernels and impurity particles should be removed.

1.1.5 Finished product After sun-drying, the almonds are the finished product. After packaging, they should be stored in a disinfected warehouse. Be careful not to store them together with other items such as spices, gasoline, alcohol and other items with off-odors or corrosive properties.

1.3 Finished product quality

The finished product quality of almonds includes 2 aspects: quality evaluation and moisture inspection.

1.3.1 Quality evaluation This refers to the inspection of almond shape, color and smell. At present, it mainly relies on visual inspection, hand feeling, smelling and tasting for comprehensive evaluation. The shape of almonds is best when the kernels are plump and uniform in size, and the color is best when it is yellow-brown, consistent in shade, and glossy. Almonds have an inherent aroma and must not carry other off-odors, such as moldy, alcoholic, or pesticide smells.

1.3.2 Moisture inspection Moisture content is one of the main indicators for evaluating almond quality. Moisture inspection can be done with a moisture meter, or by inserting a hand into a gunny sack filled with almonds: if it feels smooth and easy to insert, the almonds are relatively dry; if it feels rough and difficult to insert, the almonds have a relatively high moisture content.

2 Processing of dried apricots

2.1 Process flow

Fresh apricots -> washing -> pitting -> sulfur fumigation -> drying -> finished product.

2.2 Technical key points

2.2.1 Washing Wash fresh apricots that meet the requirements with clean water, then drain off the water.

2.2.2 Pitting After draining the fresh apricots, cut along the suture line of the flesh with a stainless steel knife, remove the apricot pits, rinse the flesh clean with clean water, and put it into baskets.

2.2.3 Sulfur fumigation Send the material baskets or bamboo trays holding apricot slices into the fumigation room, place them on wooden racks, pour burning charcoal into an iron pan in the center of the room, quickly sprinkle sulfur (4kg of sulfur per 1000kg of apricot slices) onto the charcoal, then immediately leave the fumigation room, then tightly close the doors and windows, and fumigate for about 2h. When the fruit slices become yellow and semi-transparent, open the doors and windows for ventilation. After the air has fully exchanged, move the apricot slices outdoors to air for 1h-2h, then proceed with drying.

3.2.4 Drying Send the sulfur-fumigated apricot slices into the drying room, arrange them layer by layer on wooden racks, then close the doors and windows, light a fire and supply heat for drying. During the first 4h-6h, keep the room temperature at 40°C-50°C, then gradually raise it to 70°C-80°C. As the moisture in the apricot slices evaporates and the indoor humidity rises, the doors, windows and ventilation holes should be opened in time to expel water vapor, and the closing time should be controlled according to the indoor dryness and humidity and the degree of drying of the apricot slices. During the drying process, the apricot slices on the upper and lower layers of the drying racks should be swapped to make them heated evenly, striving to dry the same batch of raw materials at the same time. The drying time is generally 24h-36h. If the temperature and humidity are not properly controlled, the drying time will be prolonged, and such products will have poor color and inferior quality.

2.2.5 Finished product Let the prepared dried apricots soften, then pick out fragments and foreign matter, carry out grading, and pack by grade in wooden boxes or cardboard boxes. Before boxing, the boxes must be lined with packaging film or packaging paper to prevent the dried apricots from absorbing moisture. After boxing, the dried apricots should be stored in an environment with a temperature of 0°C-5°C and a relative humidity of about 65%, and avoid storage in places exposed to direct sunlight.

2.3 Finished product quality

The quality requirements for finished dried apricots are orange-yellow, soft, not sticky to the hand, semi-transparent, uniform in size, neat in shape, with a rich sweet-and-sour flavor, and a moisture content not higher than 18%.

3 Processing of apricot juice

3.1 Process flow

Material selection -> washing -> crushing -> pre-cooking -> pressing -> coarse filtration -> clarification -> fine filtration -> homogenization -> deoxygenation -> adjusting sugar-acid degree -> canning -> sterilization -> finished product.

3.2 Processing key points

3.2.1 Material selection and washing The apricots used to make apricot juice should have a good flavor, slightly higher acidity, be easy to juice, yield much juice, be freestone, have orange-yellow flesh, be fully ripe, and be free of insects and damage. Before processing, wash the apricots with clean water, cut them in half, and remove the pits.

3.2.2 Crushing and pre-cooking It is best to cut the apricot flesh into small pieces of 3mm-4mm; do not cut them too finely. Pre-cook equal amounts of crushed flesh and water in a stainless steel pot for 15min-30min, controlling the temperature at 60°C-70°C, so that the flesh is fully softened. At the same time, add a little vitamin C, citric acid or a small amount of table salt to help protect the color.

3.2.3 Pressing and coarse filtration The apricot flesh after crushing and other treatments must be pressed immediately with a press. After the 1st pressing, add a small amount of water to the pomace, soak for several hours, and then press again; the expressed apricot juice is filtered through a filter mesh or filter bag to remove suspended matter and impurities.

3.2.4 Clarification and fine filtration Coarse filtration only removes large impurities and suspended matter, while clarification and fine filtration mainly remove colloids in the apricot juice, making the apricot juice clear and transparent.

3.2.5 Homogenization and deoxygenation Cloudy apricot juice must be homogenized to make the particles in the juice finer and more uniform. The apricot juice passes through homogenization small holes of 0.002mm-0.003mm under high pressure. Deoxygenation is the removal of oxygen from the apricot juice. An antioxidant method can be used, that is, adding a small amount of vitamin C and other antioxidants when canning the apricot juice.

3.2.6 Adjusting sugar-acid degree The sugar content and acid content of apricot juice must have an appropriate ratio for a good flavor. Generally, the sugar-acid ratio is 13-15:1, and the sugar content is about 17%. The adjustment method is to use filtered concentrated sugar liquid to adjust the sugar content, and use citric acid with a mass fraction of 0.1% to adjust its acidity.

3.2.7 Canning and sterilization Heat the apricot juice to 80°C-90°C, fill it into cans while hot, and seal immediately. Use boiling water high-temperature sterilization. After putting it into the pot, the water temperature rises to 100°C within 3min-5min and is maintained for about 10min. After sterilization, put the tin cans into cold water to cool rapidly. Beverages in glass bottles can be cooled by staged cooling. Wipe off water droplets and apply anti-rust oil, and the product is finished.

3.3 Finished product quality

The color of the processed apricot juice is dark yellow or orange-yellow, with a soluble solids content of 15%-20%, an acid content of 0.5%-1%, and a rich apricot fruit flavor.