CN103636769B - Quality guarantee method of dried lichees and dried longan - Google Patents

Abstract

The invention discloses a quality guarantee method of dried lichees and dried longan. The method comprises the following steps of sorting raw materials, cleaning, blanching for inactivating enzyme, and drying, thereby obtaining the semi-finished dried fruit; then putting the semi-finished products into a sealed space, and introducing ozone to carry out ozone sterilizing, thereby obtaining the dried fruit after ozone treatment; then preparing a banana skin extract; uniformly mixing the raw materials including 20%-30% of banana skin extract, 0.03%-0.06% of nisin, 0.1-0.2% of potassium sorbate, 0.01-0.03% of cinnamon essential oil and the balance of water according to the mass percentage of 100%; soaking the dried fruit after zone treatment in a membrane coating solution, fishing out, and airing by natural air, so that the membrane coating solution is cured on the surface of the dried fruit. By adopting the method, the shelf life of the dried fruit in areas with high air humidity is greatly prolonged; meanwhile, ozone treatment is adopted, so that the treatment time is short, and the amount of original bacteria on the surface of dried fruit hulls is reduced.

Description

A kind of preservation method of dried litchi and dried longan

technical field

The invention relates to a dried fruit preservation method, which belongs to the field of food processing. Specifically relates to a method for preserving quality of dried litchi and dried longan.

Background technique

Litchi and longan are tropical and subtropical special fruits, which are deeply loved by consumers. Since the problem of storage and preservation has not been completely overcome, sales in the form of fresh fruit are subject to certain restrictions. Therefore, lychee and longan are often processed into dried fruits, which are convenient for storage and sales. , and with a higher level of sweetness, it provides another taste. However, due to the dehydration during processing, dried lychees with shells and dried longan often have cracks in the shells and often appear cracks. During the subsequent storage process, it is easy to mold and deteriorate from the cracks and fruit stalks. Therefore, there is a need to develop a method for preventing the deterioration of the dried fruit in shell from the shell.

Contents of the invention

The purpose of the invention is to improve the preservation quality of dried litchi and dried longan.

The implementation method of the present invention is as follows:

(1) The raw materials are selected, and the deteriorated and cracked fruits are removed, then cleaned, blanched to inactivate the enzyme, and dried to obtain semi-finished dried fruits;

(2) Ozone sterilization: Put the semi-finished dried fruit in a sealed space, pass through ozone, and perform ozone sterilization to obtain dried fruit after ozone treatment;

(3) Preparation of banana peel extract: add water to fresh banana peel for extraction, centrifuge the feed liquid after extraction, take supernatant and concentrate to obtain banana peel extract;

(4) Preparation of fresh-keeping coating solution: based on the mass fraction of 100%, it contains 20%-30% of banana peel extract, 0.03%-0.06% of nisin, 0.1%-0.2% of potassium sorbate, and 0.01% of cinnamon essential oil -0.03%, the balance is water, dissolve the above substances in water in turn, and mix well;

(5) Coating: The dried fruit after ozone treatment is soaked in the coating solution, picked up, and dried with natural wind, so that the coating solution is solidified on the surface of the dried fruit shell.

In the above method, the raw material in step (1) is fresh litchi or fresh longan; the specific treatment of the blanching inactivating enzyme is hot water temperature 80-90°C, blanching time 8-12s.

In the above method, the ozone concentration in the sealed space in step (2) of the ozone sterilization is 4-6mg/m ³ , and the treatment time is 10-15min.

In the above method, the amount of water added in step (3) is 3-5 times the weight of fresh banana peel; the water bath extraction temperature in the extraction is 40-60°C, and the extraction time is 3-6h; the concentration In order to concentrate to a solid content of 40%-50%.

In the above method, the soaking time in step (5) is 2-4 minutes.

Compared with prior art, the present invention mainly has following advantage and effect:

1. The current dried litchi and dried longan are almost not sterilized during processing, and mildew is prone to occur in later storage. The present invention adopts scalding treatment before drying, ozone sterilization after drying combined with fresh-keeping coating liquid treatment , prolong the shelf life of dried lychee and dried longan by 30%-60%, especially greatly extend the shelf life of dried fruit in areas with high air humidity, and the shelf life of dried lychee and dried longan in bulk.

2. Litchi and longan are blanched first, which can remove the original microorganisms contaminated during the growth process, and passivate the enzyme activity, laying a solid foundation for extending the shelf life of dried fruits.

3. Short-term ozone treatment is used to reduce the number of original bacteria on the surface of the dried fruit shell.

4. The pectin, organic acid, tannin, flavonoids and other components contained in the banana peel extract use the pectin to form a film, and to a certain extent, make up the cracks produced by the fruit shell during the drying process, so as to prevent microorganisms from cracking. and the organic acids, tannins, flavonoids and other components in the banana peel extract have a synergistic antibacterial effect with nisin, potassium sorbate, and cinnamon essential oil to maintain the quality of dried litchi and dried longan.

Detailed ways

Provide two specific embodiments of the present invention below:

Embodiment one:

After fresh lychees are selected, deteriorating and cracked fruits are removed, then cleaned, blanched to inactivate the enzyme (hot water temperature 80°C, blanching time 12s), and dried, the dried fruit semi-finished product is obtained; the dried fruit semi-finished product is placed in a sealed space, Pass through ozone to make the ozone concentration in the sealed space reach 6mg/m ³ , and treat for 10 minutes to obtain litchi after ozone treatment; prepare banana peel extract, add water 5 times the weight of fresh banana peel to fresh banana peel, and extract , the water bath extraction temperature is 60°C, the extraction time is 3h, after the extraction, the feed liquid is centrifuged, the supernatant is taken, and concentrated to a solid content of 40%; the fresh-keeping coating liquid is prepared, based on the mass fraction of 100%, containing banana peel extract 30% nisin, 0.03% nisin, 0.2% potassium sorbate, 0.03% cinnamon essential oil, and the balance is water. Dissolve the above substances in water in turn and mix them evenly; soak the lychees after ozone treatment in the coating solution After 4 minutes, pick it up and dry it with natural wind, so that the coating liquid is solidified on the surface of the dried fruit shell.

Embodiment two:

After fresh longan is selected, deteriorating and cracked fruits are removed, and then cleaned, blanched to inactivate the enzyme (hot water temperature 90°C, blanching time 8s), and dried, the dried fruit semi-finished product is obtained; the dried fruit semi-finished product is placed in a sealed space, Pass into ozone, make the ozone concentration in the air reach 4mg/m ³ , process 15min, obtain the longan after ozone treatment; Prepare banana peel extract, add the water of 3 times weight with fresh banana peel to fresh banana peel, extract, The water bath extraction temperature is 40°C, the extraction time is 6h, after the extraction, the feed liquid is centrifuged, the supernatant is taken, and concentrated to a solid content of 50%; the fresh-keeping coating solution is prepared, based on the mass fraction of 100%, containing banana peel extract 20%, nisin 0.06%, potassium sorbate 0.1%, cinnamon essential oil 0.02%, and the balance is water. Dissolve the above substances in water in turn and mix them evenly; soak the longan after ozone treatment in the coating solution for 2 minutes , pick up, and dry with natural wind, so that the coating liquid is solidified on the surface of the dried fruit shell.

Put the dried lychees and dried longan products implemented according to the scheme of the present invention together with the commercially available dried dried lychees and dried longan products (without film coating) in a constant temperature and humidity chamber with a temperature of 37°C and a relative humidity of 95% to accelerate Preservation experiment, the results are as follows:

Table 1 Accelerated preservation experiment results

According to the requirements of the product standard in the agricultural industry standard NY/T709-2003 of dried lychees, the total number of bacterial colonies of the product is ≤750cfu/g, and the number of molds is ≤50cfu/g.

In the above-mentioned accelerated storage experiment with high temperature and high humidity, the dried lychees in Example 1 can be guaranteed for at least 9 days, while the dried lychees on the market can only be guaranteed for 3 days. Based on this calculation, the technical solution of the present invention can make the shelf life of dried lychees 66% longer.

In the above-mentioned accelerated storage experiment with high temperature and high humidity, the dried longan in Example 2 can be guaranteed for at least 9 days, while the commercially available dried longan can only be guaranteed for 6 days. Based on this calculation, the technical solution of the present invention can prolong the shelf life of dried longan up 33%.

In summary, compared with commercially available dried litchi and dried longan products in bulk, the technical solution of the present invention has a good inhibitory effect on the total number of bacterial colonies and the growth of mold, and can extend the product shelf life by 30%-60%.

Claims (6)

1. a keeping method for dried litchi, dried longan, is characterized in that, carries out according to the following steps:

(1) raw material are through selecting, and reject fruit that is rotten, cracking, after then cleaning, blanching inactive enzyme, dry process, obtain dry fruit semi-finished product;

(2) ozone sterilization: dry fruit semi-finished product are put into seal cavity, passes into ozone, carry out ozone sterilization, obtains the dry fruit after ozone treatment;

(3) banana tegument extract preparation: add water to fresh banana skin, extract, feed liquid centrifugation after extracting, gets supernatant, concentrated, obtains banana tegument extract; The addition of described water is in the 3-5 of fresh banana skin times weight; Water-bath extraction temperature 40-60 DEG C, extraction time 3-6h in described extraction; It is 40%-50% that described simmer down to is concentrated into solid content;

(4) preservation coating liquid preparation: according to mass fraction 100%, containing banana tegument extract 20%-30%, nisin 0.03%-0.06%, potassium sorbate 0.1%-0.2%, cinnamon essential oil 0.01%-0.03%, surplus is water, is dissolved in the water successively by above-mentioned substance, mixes;

(5) film: the dry fruit after ozone treatment is put into coating liquid and soaked, and pick up, natural wind dries up, makes coating liquid be solidificated in dry fruit shell surface.

2. the keeping method of a kind of dried litchi according to claim 1, dried longan, is characterized in that, the raw material described in step (1) are fresh lichee or fresh longan; Described blanching inactive enzyme be specifically treated to hot water temperature 80-90 DEG C, blanching treatment time 8-12s.

3. the keeping method of a kind of dried litchi according to claim 1, dried longan, is characterized in that, in step (2) described ozone sterilization, the concentration of ozone in seal cavity is 4-6mg/m ³, the processing time is 10-15min.

4. the keeping method of a kind of dried litchi according to claim 1, dried longan, is characterized in that, the time of step (5) described immersion is 2-4min.

5. the keeping method of a kind of dried litchi according to claim 1, dried longan, it is characterized in that, its concrete steps are: fresh lichee is through selecting, rejecting fruit that is rotten, cracking, then cleaning, blanching inactive enzyme, wherein hot water temperature 80 DEG C, blanching treatment time 12s, after dry process, obtains dry fruit semi-finished product; Dry fruit semi-finished product are put into seal cavity, passes into ozone, make ozone concentration in seal cavity reach 6mg/m ³, process 10min, obtains the lichee after ozone treatment; Prepare banana tegument extract, add in the water of fresh banana skin 5 times of weight, extract to fresh banana skin, water-bath extraction temperature 60 DEG C, extraction time 3h, feed liquid centrifugation after extracting, get supernatant, being concentrated into solid content is 40%; Preparation preservation coating liquid, according to mass fraction 100%, containing banana tegument extract 30%, nisin 0.03%, potassium sorbate 0.2%, cinnamon essential oil 0.03%, surplus is water, is dissolved in the water successively by above-mentioned substance, mixes; Lichee after ozone treatment is put into coating liquid and is soaked 4min, and pick up, natural wind dries up, and makes coating liquid be solidificated in dry fruit shell surface.

6. the keeping method of a kind of dried litchi according to claim 1, dried longan, it is characterized in that, its concrete steps are: fresh longan is through selecting, rejecting fruit that is rotten, cracking, then cleaning, blanching inactive enzyme, wherein hot water temperature 90 DEG C, blanching treatment time 8s, after dry process, obtains dry fruit semi-finished product; Dry fruit semi-finished product are put into seal cavity, passes into ozone, make ozone concentration in air reach 4mg/m ³, process 15min, obtains the longan after ozone treatment; Prepare banana tegument extract, add in the water of fresh banana skin 3 times of weight, extract to fresh banana skin, water-bath extraction temperature 40 DEG C, extraction time 6h, feed liquid centrifugation after extracting, get supernatant, being concentrated into solid content is 50%; Preparation preservation coating liquid, according to mass fraction 100%, containing banana tegument extract 20%, nisin 0.06%, potassium sorbate 0.1%, cinnamon essential oil 0.02%, surplus is water, is dissolved in the water successively by above-mentioned substance, mixes; Longan after ozone treatment is put into coating liquid and soaks 2min, and pick up, natural wind dries up, and makes coating liquid be solidificated in dry fruit shell surface.