Detailed Processing Technology of Sulfur-Free Low-Sugar Dried Apricots

Yanggao Jing apricot is one of the four famous apricot varieties in Shanxi Province, with a single fruit weight of 34.8g, containing vitamin C 10.4mg/100g, refractive sugar 13.1%, reducing sugar 4.7%, and acid 2.4%. This variety is the best variety for processing dried apricots; its apricot fragrance is strong, its pit yield is low, and its acid content is high, the highest among all varieties. Yanggao dried apricots are golden-yellow and translucent, with soft flesh and a sweet-sour taste, making them a premium product among preserved fruits. The products were once exported to Southeast Asia, Japan and other countries, and were praised in Japanese supermarkets as "Chinese famous precious snack" and "little golden persimmon." Yanggao dried apricots are a local specialty product beyond the Great Wall that locals delight in talking about, and have won gold awards at successive @#@117@#@ events in Hangzhou, Beidaihe and Taiyuan.

In recent years, with social development and rising living standards, people have paid increasing attention to the nutritional and health functions of food, and have become increasingly concerned about food safety and hygiene. Because traditional preserved fruits have a high sugar content, reaching as high as 70%, they are very unfavorable for people with diabetes and others who should not consume sugar. In addition, product quality among preserved fruit processing enterprises varies greatly, resulting in many preserved fruits and candied fruits on the market having severely excessive sulfur dioxide, causing harm to human health. After extensive experimentation, we adopted relatively advanced equipment and technology to research and develop sulfur-free low-sugar dried apricots. In production, sodium chloride and other substances are used instead of sulfur dioxide solution as a color-protecting agent, greatly reducing the residual sulfur dioxide content in the product; advanced vacuum sugar-infusion technology is used to not only improve the sensory quality of the product but also reduce its sugar content; in response to the problems existing in the storage of low-sulfur sugar-free preserved fruits, vacuum nitrogen-filled packaging is used, greatly extending the shelf life of sulfur-free low-sugar dried apricots and raising the product's outer packaging to a higher level. Throughout the entire production process of dried apricots, the HACCP system is introduced for control, and a corresponding HACCP management system is established, which can effectively improve the food quality and safety of dried apricot products. Dried apricots processed by this technology fully meet the requirements of national food hygiene standards and are a leisure snack that conforms to modern consumption trends.

1. Raw materials and equipment

(1) Raw materials: Yanggao Jia Jing apricots, refined white sugar, refined salt, etc.

(2) Equipment: jacketed kettle, vacuum sugar-infusion tank, hot and cold tank, drying room, steam boiler, handheld sugar refractometer, vacuum nitrogen-filled packaging machine, baking trays, Baume sugar refractometer, etc.

2. Process flow

Receiving apricots -> sorting -> removing impurities -> weighing -> cutting into halves -> pitting -> color protection -> draining -> blanching -> vacuum sugar infusion -> placing in trays to drain -> arranging on trays -> baking -> removing from room -> moisture equilibration -> shaping -> second baking -> removing from room -> moisture equilibration -> trimming and shaping -> ultraviolet irradiation sterilization -> vacuum nitrogen-filled packaging -> finished product -> inspection -> warehousing.

3. Key operation points

(1) Receiving materials: good dried apricots must come from good raw materials, with particular attention to the selection of raw material varieties. The apricot fruits are required to be fresh and plump, with moderate ripeness, free from insect damage, bruises, spots and hail damage. The most suitable apricot fruits for processing Yanggao dried apricots are Jia Jing apricots from young trees, with a fruit diameter of more than 3cm, a single fruit weight of 35g, containing vitamin C 10.37mg/100g, total acid 2.41%, dry matter 14.26%, and the best stage being 90% ripe.

(2) Sorting: the purchased raw materials are first sorted; green and overripe ones are picked out, hard green apricots are made separately into sugar apricots, soft ripe apricots are baked into dried apricots, and other mixed varieties of apricots are handled separately. After weighing, the pits are removed with a cutting knife; apricot fruits harvested on the same day should all be pitted and processed on the same day.

(3) Color protection: soak the apricot halves in a 1% sodium chloride solution by mass fraction. The purpose is to prevent enzymatic browning, protect the color of the apricot halves, and inhibit microbial activity. The soaking time is about 15min.

(4) Vacuum impregnation: prepare a sugar solution of 17 degrees Be' to 19 degrees Be' and place it in a stainless steel jacketed kettle with a capacity of 400L. The sugar solution should not be too full; it is appropriate for it to occupy 2/3 of the jacketed kettle's volume. Introduce high-pressure steam at 0.15MPa to 0.20MPa to heat the sugar solution. After the sugar solution boils, pour in the color-protected and drained apricot halves. The amount of apricot halves processed each time is 20kg to 30kg. Continue heating and boil until the tissue of the apricot halves softens (soft and mushy when pinched by hand); when the apricot halves float to the surface of the water, they can be scooped out and sent into the vacuum sugar-infusion tank. In a 500L vacuum sugar-infusion tank, about 200kg of apricot halves can be processed each time. Vacuum to 0.06MPa to 0.08MPa and maintain for 20min to 30min. Then pressurize to 0.15MPa to 0.20MPa. After returning to normal pressure, discharge from the tank into a vat, then soak in sugar solution for 24h to 72h; after scooping out, they can be arranged on trays for baking.

(5) Arranging on trays: scoop the apricot halves after the second sugar soak out of the vat, place them on dry steamer trays to drain, then arrange them on trays with the apricot halves facing down. Remove the overcooked and broken ones for separate handling. When scooping them out of the vat, be careful to scoop and place them gently and must not damage the apricot halves.

(6) Baking: place the baking trays with the arranged apricot halves on the baking rack and send them into the drying room for baking. The baking temperature upon entering the drying room must be above 50 degrees C, so as to prevent the apricot halves from becoming soft and browning. During the baking process, the temperature of the drying room should be maintained at 60 degrees C to 70 degrees C. The baking time lasts 24h. During baking, attention should be paid to releasing moisture at all times. Usually, 4 times/h to 5 times/h are needed. Baking dried apricots generally does not require turning the trays; continue baking until the moisture content of the dried apricots drops below 20%, with the degree being that they do not stick to the hand. After leaving the room, allow moisture equilibration for 2 days to 3 days, carry out shaping, remove impurities attached to the dried apricots, pinch the apricot halves into flat slices by hand, and send them into the drying room for a second baking. The drying room temperature should be maintained at 55 degrees C to 60 degrees C, and the baking time is about 18h, until the apricot slices feel elastic when pinched by hand and the moisture drops to 17% to 19%, at which point they can leave the room; after another 1 day to 3 days of moisture equilibration and shaping, they become the finished product. If the drying room temperature is too high, the fire is too fierce, or the baking time is too long, the color of the dried apricots will deepen and darken, and the grade will be lowered.

(7) Inspection and packaging: before packaging, first sterilize the trimmed and shaped dried apricots and packaging materials such as moisture-proof paper and cartons used for boxing by irradiation with ultraviolet lamp tubes, and then they can be subpackaged. In order to ensure the storage quality of sulfur-free low-sugar dried apricots, the product is best packaged with vacuum nitrogen filling. Before boxing, the dried apricots should be inspected strictly according to quality standards; spots, hard scars and lacy edges should be trimmed off, and substandard products such as off-color or thin slices should be removed; they are packed into polyethylene eco-friendly plastic boxes, 150g per box, with a fruit fork added, a label affixed, and the production date stamped before boxing.

4. Quality requirements

(1) Sensory indicators: 1) Color standard. Grade I is orange-red, with the maximum diameter of each slice not less than 2.5cm; Grade II is deep orange-red, allowed to have a small amount of greenish slices, with the maximum diameter of each slice not less than 2.3cm. 2) Taste and mouthfeel. Rich apricot aroma, pleasant sweet-sour taste, no off-flavor, good mouthfeel. 3) Tissue form. Thick flesh, no coarse fiber, soft exterior, with skin and without pit, slice-shaped, naturally smooth and clean surface, no injuries, no scars, no wrinkled skin, semi-translucent, no syrup leakage, no sugar return, no breakage, no cracked skin, uniform and neat in size, free from insect damage.

(2) Physicochemical indicators: total sugar content not less than 50%, maximum sulfur dioxide residue not more than 50mg/kg, moisture 17% to 19%, acid content 2.78%, vitamin C 3.6mg/100g, copper not more than 5mg/kg; arsenic not more than 0.1mg/kg, lead not more than 1mg/kg, and neither benzoic acid nor sodium saccharin may be detected.

(3) Microbiological indicators: total bacterial count not more than 400/g, mold count not more than 25/g, coliform bacteria not more than 15/100g, and hemolytic streptococcus, Staphylococcus aureus, Shigella and Salmonella must not be detected.

(4) Pesticide residues: BHC not more than 0.05mg/kg, DDT not more than 0.05mg/kg.