Processing method for preserved fruits by cold impregnation

A processing method for preserved fruits by cold impregnation, comprising following steps:

• 1) washing and cutting fruits to obtain processed fruits;
• 2) subjecting the processed fruits to partial dehydration, thereby obtaining partially dehydrated fruits, wherein a mass of the partially dehydrated fruits is 50% to 80% of a mass of the processed fruits before dehydration;
• 3) immersing the partially dehydrated fruits in a color-protecting and firming mixed sugar solution and conducting a vacuum treatment to obtain vacuum-treated fruits;
• wherein
• the color-protecting and firming mixed sugar solution comprises a mixed sugar solution, a color-protecting agent, and a firming agent, the mixed sugar solution is prepared by mixing mixed sugar and water in a ratio of 1:(1.5-2) and has a sugar content of 30% to 35%;
• the mixed sugar in the mixed sugar solution comprises malt syrup and granulated sugar, and the malt syrup and the granulated sugar are at a mass ratio of 1:9 to 3:7;
• a mass of the color-protecting agent is 0.3% to 0.5% of a mass of the mixed sugar solution, and a mass of the firming agent is 0.01% to 0.03% of the mass of the mixed sugar solution;
• 4) placing the vacuum-treated fruits together with the color-protecting and firming mixed sugar solution into a sugar permeation device to conduct first low-temperature sugar permeation at −2° C. to 0° C., thereby obtaining a mixture of first low-temperature sugar-permeated preserved fruits and the color-protecting and firming mixed sugar solution;
• 5) supplementing the mixed sugar into the mixture of the first low-temperature sugar-permeated preserved fruits and the color-protecting and firming mixed sugar solution until a mass concentration of the mixed sugar solution in the sugar permeation device reaches 40% to 45%, introducing carbon dioxide into the sugar permeation device, and sealing to conduct second low-temperature sugar permeation at −5° C. to −2° C., thereby obtaining a mixture of second low-temperature sugar-permeated preserved fruits and the color-protecting and firming mixed sugar solution;
• 6) supplementing the mixed sugar into the mixture of the second low-temperature sugar-permeated preserved fruits and the color-protecting and firming mixed sugar solution until the mass concentration of the mixed sugar solution in the sugar permeation device reaches 55% to 60%, introducing carbon dioxide into the sugar permeation device, and sealing to conduct third low-temperature sugar permeation at −8° C. to −5° C., thereby obtaining a mixture of third low-temperature sugar-permeated preserved fruits and the color-protecting and firming mixed sugar solution;
• and
• 7) taking out the preserved fruits from the mixture of the third low-temperature sugar-permeated preserved fruits and the color-protecting and firming mixed sugar solution, draining off the color-protecting and firming mixed sugar solution, and drying to obtain the preserved fruits after the cold impregnation.