What are the latest deep-processing methods for plums?
Plums have a very high yield per unit area and are nutritious, containing carbohydrates, protein, pectin, and a large amount of vitamin C. The price per kilogram of plums also exceeds that of apples. Under these circumstances, more and more new plum orchards are being established, and the area keeps growing larger. Besides being eaten fresh, plums can be made into candied fruit and canned fruit in syrup, as well as juice, dried fruit, and jam. Their processed product, jiayingzi (preserved plums), sells well in Southeast Asia and other places, making plums one of the important fruits for foreign trade export.
(1) Processing flow
Raw material selection → salting → sun-drying → grading → rinsing → ingredient mixing → sugar absorption → boiling → returning to the vat for soaking → sun-drying → packaging.
(2) Key operation points
(1) Raw materials: The red-hearted plum is the suitable processing variety. Harvest when the fruit is fully swollen and the skin begins to color and has a glossy sheen. If overripe, the fruit becomes soft, which is not good for processing. Remove insect-damaged fruit.
(2) Salting: Use 10-12 kg of table salt per 100 kg of fresh fruit. First rub the skin lightly with salt to help the salt penetrate the flesh, then place one layer of fresh plums and one layer of salt in a vat and press down to cure. After 20 days, take them out and filter off the brine.
If there are many plums, a plum-shaking machine can be used for semi-mechanized processing. The rotation speed of the plum-shaking machine should be adjusted to 330-350 rpm, adding 25-30 kg of plums and 100-150 g of plant ash each time. Shake for 5-10 minutes, and once the green surface of the plums is rubbed broken, they can be poured out. After draining for 10 minutes, rinse clean with clear water, spread thinly to dry in the sun, and when the plums turn brown, they can be put into the tank for salting.
(3) Sun-drying: After salting for 10-plus days, if good weather comes, they can be put out in the sun to dry, which will produce a better color. When dried to a moisture content of 33-35%, they can be brought indoors and piled up so that the moisture inside and outside the fruit balances out.
(4) Grading: Pick out broken and insect-damaged plums as substandard products. Divide into three grades by size: grade one at 150 or fewer per kg, grade two at 250 or fewer per kg, and the rest as grade three.
(5) Rinsing: Rinse the plums in clear water to remove the salt, until only slightly salty. Then sun-dry until 70% dry, and remove the pits.
(6) Ingredients: 100 kg of plums, 50 kg of granulated sugar, 10 kg of licorice, 800 g of fennel, 1 kg of guiertong, 200 g of orange peel oil, 40 g of sodium benzoate, and an appropriate amount of citric acid.
(7) Sugar absorption: First boil the licorice and fennel into a thick juice, add an appropriate amount of sugar and sodium benzoate, and make a 60% thick sugar liquid. Pour the sugar liquid over the plums, add an appropriate amount of citric acid according to different tastes, and once all the plums have absorbed enough sugar liquid, they can be put into the pot for boiling.
(8) Boiling: Pour the plums together with the sugar liquid into the pot, heat to boiling, and boil until the flesh is cooked through and soft.
(9) Returning to the vat for soaking: While hot, pour them back into the vat and soak for 5-7 days. After the flesh has absorbed enough sugar liquid, filter out the sugar liquid that soaked the flesh. Then take out the flesh and dry it in the sun.
(10) Sun-drying: Place the plums that have absorbed enough sugar liquid on bamboo trays and expose them to sunlight for 2-3 days, or send them to a drying room at 55-60°C and dry until 70% dry. After drying, mix in orange peel oil, sugar, and other seasonings.
(11) Packaging: Pack in 0.5 kg plastic film food bags, seal, and then place in cartons.
(3) Quality requirements
The finished product is full of sweet, fragrant thick juice, with a rich aroma, glossy color, fine texture, appropriate softness and hardness, suitable sweetness and sourness, and very tasty. Sugar content reaches 58-63%, and it is 70% dry.