Processing Technology and Production Methods for Pear Preserves

1. Selection and Processing of Raw Materials

Raw materials with large fruit shape, small core, relatively high acidity, and no significant browning are better for boiling-resistant varieties. Generally, harvest when the fruit is ripe and relatively firm, grade by size and maturity, and remove insect-damaged, diseased, and rotten fruit. Peel, cut in half, remove the core, then soak in a mixed solution containing 0.1% calcium chloride (or 1.5% lime solution) and 0.2%-0.3% sodium sulfite for hardening and sulfur treatment for 10-15 hours. Firm-fleshed fruits are only soaked in sulfur, without hardening treatment. After treatment, the fruit must be thoroughly rinsed before sugar processing to remove residual sulfur and lime.

2. Sugar Processing

Pear tissue is relatively dense, so the method of multiple sugar additions and single-boiling is generally used. That is, first prepare about 25 kg of sugar solution at 35%-40% concentration in a pot, bring to a boil, then pour in 50-60 kg of the treated pears, and after boiling, add about 5 kg of cold sugar solution at 50% concentration. Repeat this three times, with about 10 minutes between each addition. When wrinkles appear on the surface of the fruit pieces and the flesh swells, sugar can be added for boiling. Sugar is added in six batches: 5 kg each for the first and second, 6 kg each for the third and fourth, along with a small amount of cold sugar solution to temporarily stop the boiling in the pot, slightly lower the temperature, reduce the internal water vapor pressure of the fruit pieces, which helps sugar penetration and dehydration, and accelerates the sugar processing. For the fifth addition, only 6 kg of sugar is added, with about 5 minutes between each sugar addition, all done while boiling. For the sixth addition, 7 kg of sugar is added, then boil for another 20 minutes. When the flesh turns light yellow, pour it together with the sugar solution into a vat and soak for about 48 hours. When the fruit pieces are transparent and shiny, remove from the vat and dry.

3. Drying, Shaping, and Packaging

After soaking, remove the fruit pieces, drain excess sugar solution, spread on drying trays, and place in a drying room. Dry at 60-65°C until the surface of the fruit pieces is no longer sticky to the touch, slightly elastic, and brownish-yellow, with a moisture content of 15%-18%. Remove, discard rotten pieces, scars, and defective pieces that have not absorbed sugar, then shape the qualified pieces into flat rounds and pack them in moisture-proof paper or plastic boxes for crating. In our country, it has a long history and is a famous specialty sold well at home and abroad. Its advantages are greatly reduced weight, significantly reduced volume, easy transportation, longer storage, convenient consumption, and rich nutrition, making it very popular among explorers, sailors, and tourists.

Process Flow

Raw material selection → washing fruit → drying → packaging

Key Operation Points

a. Raw material selection For dried fresh grapes, it is advisable to choose seedless varieties with high solid content, good flavor and color, no serious enzymatic browning, suitable maturity, thin skin, soft flesh, and sugar content above 20%.

b. Washing and decontamination Generally, wash with 1.5-4.0% sodium hydroxide solution to remove the waxy substance and harmful microorganisms attached to the grape skin. At the same time, it can also disinfect and cause small cracks to appear on the skin, which facilitates moisture evaporation and promotes drying.

c. Drying is divided into natural drying and artificial drying.

Natural drying: Place the treated and washed raw materials on drying trays and sun-dry for 3-5 days, then turn over and continue drying for 2-3 days. Then stack the drying trays in a ventilated room to dry in the shade for about 30 days. The product has a bright green color and excellent quality. Then store for softening for more than 3 weeks, remove from stems and thresh, and package. The advantages of natural drying are simple equipment and lower cost, but it is limited by climate, the drying time is too long, and product quality is easily reduced.

Artificial drying must have good heating and insulation, ventilation and moisture-dissipation equipment, as well as good sanitary conditions. This can greatly shorten the drying time and ensure yield and quality. However, the cost is relatively high and the operation technology is relatively complex. At present, many grape drying units at home and abroad are gradually developing toward artificial drying.