CN103355399A - Method for prolonging storage period of litchis - Google Patents

Method for prolonging storage period of litchis Download PDF

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Publication number
CN103355399A
CN103355399A CN2013103030860A CN201310303086A CN103355399A CN 103355399 A CN103355399 A CN 103355399A CN 2013103030860 A CN2013103030860 A CN 2013103030860A CN 201310303086 A CN201310303086 A CN 201310303086A CN 103355399 A CN103355399 A CN 103355399A
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China
Prior art keywords
lichee
freezing
vacuum
high pressure
litchis
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Pending
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CN2013103030860A
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Chinese (zh)
Inventor
孙大文
曾新安
胡芬
王启军
高文宏
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South China University of Technology SCUT
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South China University of Technology SCUT
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Priority to CN2013103030860A priority Critical patent/CN103355399A/en
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Pending legal-status Critical Current

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Abstract

The invention discloses a method for prolonging the storage period of litchis. Vacuum packed fresh litchis are subjected to high pressure freezing, and are then put in storage and frozen. The high pressure freezing specifically includes: under a high pressure condition of 200-400MPa, lowering the temperature to a range from -18DEG C to -20DEG C, and then releasing the pressure to atmospheric pressure within 2-5s. According to the method for prolonging the storage period of litchis involved in the invention, after one-year freezing, the unfrozen litchis have almost the same quality to that of fresh fruits, small juice leakage, and no obvious change on the skin color.

Description

A kind of method that prolongs the Litchi storage phase
Technical field
The present invention relates to the frozen food technology field, particularly a kind of method that prolongs the Litchi storage phase.
Background technology
The fresh lichee fruits nutrition is worth high, summer High Temperature maturation in season, and metabolism is vigorous, adds structure and physiological property that it is special, adopts rear perishable going bad, and brown stain often occurs easily, has limited its way far away transportation and sale, has restricted the developing of regional market.At present the physiological change that brown stain is fruit self appears in pericarp, and the factor that causes Litchi fruit browning mainly contains and adopts front environmental condition, maturity, courses of infection, damages to plants caused by sudden drop in temperature, mechanical damage, fire damage, naturally-aged etc.
Chinese patent CN02134343.8 announced a kind of take the mechanization standard operation as the basis harvesting, fresh fruit low-temperature transport, Pesticidal and sterilizing, film, pack, put in storage a series of technology such as refrigeration, make the fresh litchi shelf-life reach preservation method more than 40~50 days.Chinese patent CN02115089.3 has announced and ripe fresh lichee fruit is carried out high-temperature-hot-water has soaked in short-term fruit and process, in pericarp keeping fresh and protecting color liquid, soak again, then at low temperatures storage so that the lichee low-temperature preservation phase reach 50~80 days method.Chinese patent CN97105377.4 has announced antistaling agent, the fresh fruit one that will be comprised of oxysalt and the auxiliary agent of sulphur and has put up sealing vanning to the polybag, and fresh keeping time reaches 10~15 days at normal temperatures, the pericarp nondiscolouring, and pulp is not spoiled.
In traditional freezing method, freezing rate is one of key factor that affects the frozen food quality.Cross slow freezing rate, thereby can cause that the ice crystal that produces is excessive to cause mechanical damage to food cells, cause ingredients from lossing in the born of the same parents.Enzyme, microorganism and oxidation also can make food occur to go bad simultaneously.If freezing rate too fast (for example ultralow temperature freezes-40 ℃), the outer of food freezes rapidly, subsequently when inner freezing, understand because of the increase of volume so that outside frozen crust breaks, and such freezing process that occurs from outside to inside, can make the inside of frozen food produce thick ice crystal, the quality of food is caused harmful effect.
In sum, existing conventional method about the preservation fresh lichee has such as the deficiency directly into existence such as Cold storage in the refrigerator, antistaling agent preservations:
(1) traditional method for preserving can not effectively slow down the browning reaction of lichee pericarp, so that the preservation time of fresh fruit lichee shortens dramatically;
(2) traditional method for preserving is after preservation lichee a period of time, and the quality of lichee can reduce rapidly along with the growth of preservation time, and after storing a period of time, the qualities such as the color, smell and taste of lichee often are much worse than fresh fruit;
(3) although can be in establishment browning reaction under the low temperature environment for the lichee of traditional freezing method preservation, but because lichee produces thick ice crystal in refrigerating process, volumetric expansion, cell tissue to lichee causes very large damage, lichee juice turnover rate after thawing is large, quality reduces, and can go bad rapidly at short notice.
Summary of the invention
In order to delay its browning reaction, increase the Litchi storage time, guarantee to separate the quality of frozen litchee, reduce since bad method for preserving so that the reduction of lichee quality in preserving process the object of the present invention is to provide a kind of method that prolongs the Litchi storage phase, frozen custard structure, the quality that obtains is constant, enzymatic activity reduces, after the cold storage 1 year, lichee quality and fresh fruit after thawing are almost unchanged, and the juice loss rate is little, and significant change does not occur lichee epidermis color and luster.
Purpose of the present invention is achieved through the following technical solutions by the following technical programs:
A kind of method that prolongs the Litchi storage phase, with vacuum-packed fresh fruit lichee carry out high pressure freezing after, put in storage freezing; Described high pressure is freezing to be specially: under the condition of high voltage of 200~400MPa, cool the temperature to-18~-20 ℃, then in 2-5s release pressure to normal pressure.
Described vacuum packaging is specially: the fresh lichee after will sorting carries out vacuum packaging, every packed lichee 500g, and vacuum is 0.08MPa.
Described warehouse-in is freezing to be specially: in the medium-term and long-term storage of-18 ℃ of freezers.
With vacuum-packed fresh fruit lichee carry out high pressure freezing before, also vacuum-packed fresh fruit lichee is carried out precooling.
Described precooling is specially: be pre-chilled to 4 ℃.
Principle of the present invention is as follows: the crystallization of water under normal pressure, i.e. and I type ice crystal, the density ratio aqueous water of its ice is little, causes freeze volume to increase, and this can cause tissue damage when freezing.And water forms the large II type of density ratio water-VI type ice crystal when under high pressure freezing, and crystal structure is also complicated.The high pressure food Refrigeration Technique utilizes the change of pressure to control the transformation behavior of water in the food, and (under 200~400MPa), in phase transition process, high pressure ice (ice II-IX) volume does not increase, so can reduce the damage to tissue at condition of high voltage.The freezing preservation of food can effectively utilize the phase transformation of water, by the external control temperature and pressure reach change food the physics state can purpose, being lower than 0 ℃ of water under the high pressure has a non-freezing zone.After pressure disappears, just can obtain a supercooling, the result ices exactly nucleation rate and sharply increases.Food is cooled to uniform temperature, and this moment, water did not still freeze, then rapid pressure relief, at the inner little and uniform ice crystal of granularity that forms of food, and the ice crystal volume can not expand, and can reduce the damage to food tissue inside, obtains to keep the frozen food of original food quality.
Compared with prior art, the present invention has the following advantages and beneficial effect:
(1) frozen custard that makes of the present invention, its ice crystal 90% is distributed in the lichee cell, is distributed in the lichee iuntercellular and flood its ice crystal of freezing lichee 70%, only has 30% in cell.
(2) frozen custard that makes of the present invention, lichee quality and fresh fruit after thawing are almost unchanged, and the juice loss rate has reduced (P<0.05) more than 40% than dipping is freezing.
(3) after 10 months, significant change does not occur to the lichee of the method quick-frozen in lichee epidermis color and luster in cold storage, and the lichee of dipping freezing then under the same conditions cold storage namely begins to occur brown stain after 3 months, and obvious visible variation occurs fruit colour.
The specific embodiment
Below in conjunction with embodiment, the present invention is described in further detail, but embodiments of the present invention are not limited to this.
Embodiment 1
Buy the ripe fresh glutinous rice wrapped in lotus leaves lichee that is no more than 24h after adopting, clean, pick the raw material lichee of the unsuitable cold storage of corruption, brown stain, breakage etc. of removal.Put into laminated film bag, vacuum seal, every packed lichee 500g, vacuum is 0.08MPa.Then be chilled in advance 4 ℃, it is freezing that the good glutinous rice wrapped in lotus leaves lichee of getting precooling carries out high pressure, after pressure is risen to 350MPa and cools to-20 ℃ in 2s release pressure to normal pressure.The ice crystal 95% that forms is distributed in the cell, and the glutinous rice wrapped in lotus leaves lichee that the rear juice loss rate of thawing is compared the dipping freezing has reduced 45%(P<0.05), in-18 ℃ of freezer cold storage obvious quality still occuring in 10 months changes.
Embodiment 2
Buy and pluck the ripe fresh osmanthus flavor lichee that is no more than 24h, clean, pick the raw material lichee of the unsuitable cold storage of corruption, brown stain, breakage etc. of removal.Put into laminated film bag, vacuum seal, every packed lichee 500g, vacuum is 0.08MPa.Then be chilled in advance 4 ℃, getting the good osmanthus of precooling flavor lichee, to carry out high pressure freezing, after pressure is risen to 400MPa and cools to-20 ℃ in 4s release pressure to normal pressure.The ice crystal 90% that forms is distributed in the cell, and the rear juice loss rate of thawing is compared the freezing osmanthus flavor lichee of dipping and reduced 50%(P<0.05), obvious change color did not still occur in 1 year in-18 ℃ of freezer cold storage.
Embodiment 3
Buy and pluck the ripe fresh black leaf lichee that is no more than 24h, clean, pick the raw material lichee of the unsuitable cold storage of corruption, brown stain, breakage etc. of removal.Put into laminated film bag, vacuum seal, every packed lichee 500g, vacuum is 0.08MPa.Then be chilled in advance 4 ℃, it is freezing that the good black leaf lichee of getting precooling carries out high pressure, after pressure is risen to 200MPa and cools to-18 ℃ in 5s rapidly release pressure to normal pressure.The ice crystal 95% that forms is distributed in the cell, and the rear juice loss rate of thawing is compared the freezing black leaf lichee of dipping and reduced 60%(P<0.05), obvious change color did not still occur in 8 months in-18 ℃ of freezer cold storage.
Above-described embodiment is the better embodiment of the present invention; but embodiments of the present invention are not limited by the examples; other any do not deviate from change, the modification done under Spirit Essence of the present invention and the principle, substitutes, combination, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.

Claims (5)

1. a method that prolongs the Litchi storage phase is characterized in that, with vacuum-packed fresh fruit lichee carry out high pressure freezing after, put in storage freezing; Described high pressure is freezing to be specially: under the condition of high voltage of 200~400MPa, cool the temperature to-18~-20 ℃, then in 2-5s release pressure to normal pressure.
2. the method for prolongation Litchi storage phase according to claim 1 is characterized in that, described vacuum packaging is specially: the fresh lichee after will sorting carries out vacuum packaging, every packed lichee 500g, and vacuum is 0.08MPa.
3. the method for prolongation Litchi storage phase according to claim 1 is characterized in that, described warehouse-in is freezing to be specially: in the medium-term and long-term storage of-18 ℃ of freezers.
4. the method for prolongation Litchi storage phase according to claim 1 is characterized in that, with vacuum-packed fresh fruit lichee carry out high pressure freezing before, also vacuum-packed fresh fruit lichee is carried out precooling.
5. the method for prolongation Litchi storage phase according to claim 4 is characterized in that, described precooling is specially: be pre-chilled to 4 ℃.
CN2013103030860A 2013-07-18 2013-07-18 Method for prolonging storage period of litchis Pending CN103355399A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105564816A (en) * 2015-12-31 2016-05-11 华南理工大学 Fresh-keeping and protective packing used for vulnerable fruits and preparation method of packing
CN107361126A (en) * 2017-08-02 2017-11-21 合肥浦邦农业科技有限公司 A kind of preparation technology of dried litchi
CN107683891A (en) * 2017-08-29 2018-02-13 华南理工大学 A kind of method and apparatus of liquid carbon dioxide high pressure freezing fresh food
CN107889876A (en) * 2017-11-29 2018-04-10 陆滔 A kind of anxious jelly method for keeping meat products nutrition

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EP1854364A1 (en) * 2006-05-09 2007-11-14 Nestec S.A. High pressure freezing of frozen desserts
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EP1854364A1 (en) * 2006-05-09 2007-11-14 Nestec S.A. High pressure freezing of frozen desserts

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105564816A (en) * 2015-12-31 2016-05-11 华南理工大学 Fresh-keeping and protective packing used for vulnerable fruits and preparation method of packing
CN105564816B (en) * 2015-12-31 2018-09-14 华南理工大学 A kind of fresh-keeping and protective packaging and preparation method thereof for rapid wear fruit
CN107361126A (en) * 2017-08-02 2017-11-21 合肥浦邦农业科技有限公司 A kind of preparation technology of dried litchi
CN107683891A (en) * 2017-08-29 2018-02-13 华南理工大学 A kind of method and apparatus of liquid carbon dioxide high pressure freezing fresh food
CN107889876A (en) * 2017-11-29 2018-04-10 陆滔 A kind of anxious jelly method for keeping meat products nutrition

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Application publication date: 20131023