阅读说明：本技术 秋葵涂膜气调复合保鲜方法 (Coating air-conditioning composite fresh-keeping method for okra ) 是由 何国菊 于 2021-01-03 设计创作，主要内容包括：本发明公开了一种秋葵涂膜气调复合保鲜方法,属于果蔬保鲜方法；旨在提供一种保鲜效果好、操作简单的秋葵保鲜方法。该方法是将秋葵在复合保鲜涂膜液中浸渍1分钟,自然晾干后装于保鲜袋中室温下MA贮藏,贮藏第3天在保鲜袋的两面分别穿刺两行长度为20㎝的孔组；保证行间距10㎝、孔间距4㎝、孔直径0.6㎜；所述复合保鲜涂膜液中的植酸含量为0.05%,二氧化氯含量为2g/L,改性魔芋葡甘聚糖含量为0.3%。经本发明方法处理的秋葵贮藏第19天的Vc含量仍保持了61%,叶绿素含量为0.095mg.g～(-1),纤维素含量为0.72%,MDA含量为对照组的59%,商品率可达到80%；说明本发明方法能有效延缓秋葵采后的成熟衰老。(The invention discloses a coating air-conditioning composite preservation method for okra, belonging to a fruit and vegetable preservation method; aims to provide a fresh-keeping method for okra, which has good fresh-keeping effect and simple operation. The method comprises the steps of immersing okra in a composite fresh-keeping coating liquid for 1 minute, naturally airing, then placing in a fresh-keeping bag for MA storage at room temperature, and respectively puncturing two rows of holes with the length of 20 cm on two sides of the fresh-keeping bag at the 3 rd day of storage; the line spacing is guaranteed to be 10 cm, the hole spacing is guaranteed to be 4 cm, and the hole diameter is guaranteed to be 0.6 mm; the phytic acid content in the composite fresh-keeping coating liquid is 0.05%, the chlorine dioxide content is 2g/L, and the modified konjac glucomannan content is 0.3%. The Vc content of okra treated by the method of the invention at 19 days of storage is still kept at 61%, and the chlorophyll content is 0.095mg.g ‑1 CelluloseThe content is 0.72 percent, the MDA content is 59 percent of that of a control group, and the commodity rate can reach 80 percent; the method can effectively delay the mature and aging of the okra after being picked.)

1. A coating air-conditioning composite preservation method for okra is characterized in that the method comprises the steps of soaking okra in a composite preservation coating liquid for 1 minute, naturally airing, then placing in a preservation bag for MA storage at room temperature, and respectively puncturing two sides of the preservation bag to form two rows of holes with the length of 20 cm on the 3 rd day of the storage period; the punch group line spacing is guaranteed to be 10 cm, the hole spacing is guaranteed to be 4 cm, and the hole diameter is guaranteed to be 0.6 mm; the phytic acid content in the composite fresh-keeping coating liquid is 0.05%, the chlorine dioxide content is 2g/L, and the modified konjac glucomannan content is 0.3%.

2. The okra film-coating controlled atmosphere composite preservation method according to claim 1, characterized in that the modified konjac glucomannan is prepared by the following method: preparing 0.3% solution of konjac glucomannan, performing constant-temperature water bath at 60 ℃, adding 1% lecithin after stirring and swelling for 80 minutes, and stirring in the water bath; adding calcium hydroxide to adjust pH to 10, adding 0.5% glycerol, and stirring for swelling for 20 min.

Technical Field

The invention relates to an okra preservation method, in particular to a coating air-conditioning composite preservation method for okra; belongs to a fresh-keeping method of fruits and vegetables.

Background

Okra is a vegetable with high nutritive value and medical health care efficacy, and is eaten mainly as tender fruit in high-temperature seasons. Okra has developed pores, loses water and breathes quickly in high-temperature seasons, is easy to yellow and fiberize, loses commodity value and severely restricts sales. At present, the ecological preservation method of okra mainly seeks some safe and effective preservative under the non-cold-damage low-temperature storage condition. However, the cold chain technology has high energy consumption, strong technical performance and high investment cost, and the temperature fluctuation in the processes of storage, transportation and sale easily causes cold damage to fruits and vegetables during the mature period, thereby causing rottenness and deterioration.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the coating air-conditioning composite preservation method for the okra, which has good preservation effect and simple operation.

In order to achieve the purpose, the invention adopts the following technical scheme: soaking okra in the composite fresh-keeping coating liquid for 1 minute, naturally airing, then placing in a fresh-keeping bag, storing at room temperature MA, and respectively puncturing two sides of the fresh-keeping bag to form two rows of hole groups with the length of 20 cm on the 3 rd day of storage; the line spacing is guaranteed to be 10 cm, the hole spacing is guaranteed to be 4 cm, and the hole diameter is guaranteed to be 0.6 mm; the phytic acid content in the composite fresh-keeping coating liquid is 0.05%, the chlorine dioxide content is 2g/L, and the modified konjac glucomannan content is 0.3%.

In the technical scheme, the modified konjac glucomannan is prepared by the following method: preparing 0.3% solution of konjac glucomannan, performing constant-temperature water bath at 60 ℃, adding 1% lecithin after stirring and swelling for 80 minutes, and stirring in the water bath; adding calcium hydroxide to adjust pH to 10, adding 0.5% glycerol, and stirring for swelling for 20 min.

Compared with the prior art, the invention adopts the technical scheme to carry out fresh-keeping treatment on the okra, so that the reduction of Vc and chlorophyll content of the stored okra can be remarkably delayed (P is less than 0.05), the increase of cellulose and MDA content is inhibited, and the reduction of the commodity rate of the stored okra is avoided. Experiments prove that the Vc content of the okra treated by the method disclosed by the invention on the 19 th day is still kept 61%, which is 4 times higher than that of a control group (okra not subjected to preservation treatment); chlorophyll content of 0.095mg.g^-115 times of the control group; the cellulose content is 0.72 percent and is less than 30 percent of that of a control group; the MDA content is 59% of that of the control group; the commodity rate can reach 80 percent, which is 8 times of that of the control group. The method can effectively delay the mature and aging of the okra after being picked.

In addition, the konjac glucomannan is modified, so that the fishy smell of the konjac fine powder can be removed, the solubility is increased, the sol stability is enhanced, the acetyl groups on konjac glucomannan molecules can be removed, the intermolecular hydroxyl hydrogen bond mutual crosslinking is facilitated, the film forming toughness is enhanced, and the film forming performance is better.

Drawings

FIG. 1 is a bar graph of the effect of different treatment regimes on okra chlorophyll content;

FIG. 2 is a graph showing the effect of the puncture time of the freshness protection package on the chlorophyll content of the stored okra;

FIG. 3 is a graph showing the effect of soaking time of preservative coating solution on chlorophyll content of stored okra;

FIG. 4 is a graph of the change in chlorophyll content of stored okra under optimized parameters;

FIG. 5 is a graph of the variation of cellulose content of stored okra under optimized parameters;

FIG. 6 is a graph showing the Vc content variation of okra stored under optimized parameters;

FIG. 7 is a graph of MDA content variation for storage of okra under optimized parameters;

FIG. 8 is a graph showing the effect of the commercial rate of okra storage under optimized parameters.

Detailed Description

The invention is further illustrated by the following specific examples, which are set forth below:

1) selecting and picking okra which is 5-6 days after flowering and 8-9 cm long in pod length, and pre-cooling for 1 hour in a room temperature environment;

2) soaking the precooled okra in the composite fresh-keeping coating liquid for 1 minute, and naturally drying the okra after being fished out; the phytic acid content in the composite fresh-keeping coating liquid is 0.05 percent, the chlorine dioxide content is 2g/L, and the modified konjac glucomannan content is 0.3 percent;

3) sealing the dried okra in a polyethylene freshness protection package with the thickness of 0.01 mm, and storing the okra in a MA mode at room temperature;

4) and on the storage 3 th day, two lines of hole groups with the length of 20 cm are respectively formed by puncturing on two sides of the freshness protection package, so that the line spacing of 10 cm, the hole spacing of 4 cm and the hole diameter of 0.6 mm are guaranteed.

In the embodiment, the modified konjac glucomannan is prepared by the following method: preparing 0.3% solution of konjac glucomannan, performing constant-temperature water bath at 60 ℃, adding 1% lecithin after stirring and swelling for 80 minutes, and stirring in the water bath; adding calcium hydroxide to adjust pH to 10, adding 0.5% glycerol, and stirring for swelling for 20 min.

The method comprises the following experiments that the okra is coated by the fresh-keeping coating liquid at room temperature (15-23 ℃), then is put into a fresh-keeping bag, and the fresh-keeping effect of the okra is realized by combining MA storage conditions:

experiment-influence of fresh-keeping coating liquid composition on chlorophyll content of autumn sunflower

The fresh-keeping coating liquid comprises nine processing steps: water for control treatment one; treating with 0.25% phytic acid solution; treating the third step to be 2.5mg/L chlorine dioxide solution; treating the fourth step to obtain a 2g/L modified konjac glucomannan solution; treating with composite solution containing phytic acid 0.05% and chlorine dioxide 2 mg/L; sixthly, the treatment is a composite solution, wherein the composite solution contains 0.25 percent of phytic acid and 2g/L of modified konjac glucomannan; treating with composite solution containing 2.5mg/L chlorine dioxide and 2g/L modified konjac glucomannan; and the eighth treatment is a composite solution which contains 0.05 percent of phytic acid, 2g/L of chlorine dioxide and 2g/L of modified konjac glucomannan. The nine treatment steps are composite solution containing phytic acid 0.05%, chlorine dioxide 2g/L and konjaku glucomannan 2 g/L.

The fresh okra without damage is divided into nine groups, and each group contains 20 okra. And correspondingly placing each group of okra into the first treatment to the ninth treatment for soaking for 2min, taking out, naturally drying, respectively placing into nine freshness protection packages for normal-temperature storage (13-20 ℃, relative humidity of 65-80%, the same below), and respectively detecting the chlorophyll content of 0 day (the day of just picking), 3 days and 9 days of storage, wherein the detection result is shown in figure 1.

Comparing the three corresponding series of the day 0, the day 3 and the day 9, taking the day 0 as a reference, the chlorophyll content of each treatment group in the day 9 is more rapidly reduced than that of the day 3, and the chlorophyll content of the okra in each treatment group is reflected to be in a trend of reduction along with the prolonging of the storage time.

However, the chlorophyll decreased at different rates among the treatment groups. The content of octa-chlorophyll is reduced least and slowest, the coating liquid contains three substances of phytic acid, chlorine dioxide and modified konjac glucomannan at the same time, and the coating preservation effect is the best; compared with the first treatment, the chlorophyll is reduced obviously and slowly, which shows that the okra is preserved to a certain extent by adding konjac glucomannan, chlorine dioxide or phytic acid into the coating liquid; the difference between the second and third treatments and the fourth, sixth, seventh, eighth and ninth treatments is that the modified konjac glucomannan is added in the latter. According to the experimental result, the chlorophyll content can be slowed down by adding the modified konjac glucomannan; compared with each treatment group on the 9 th day, the chlorophyll content is at least improved by 26 percent after the substance is added, which indicates that the addition of the film-forming agent konjac glucomannan is necessary, and is beneficial to the fresh keeping of the okra; the experimental results also show that the chlorine dioxide and the phytic acid play a role of a physiological activity regulator for the coating preservation of the okra. Compared with the treatment five, the chlorophyll is reduced more slowly, which shows that the addition of the chlorine dioxide and the phytic acid in the film forming liquid is better than the fresh fruit fresh-keeping by using a single film forming agent, and the addition of the chlorine dioxide and the phytic acid has greater necessity in the fresh-keeping of the okra. Comparing the second treatment, the third treatment and the fifth treatment, the better composite use effect of the chlorine dioxide and the phytic acid is shown; compared with the processing method of nine, the difference is that the film forming agent used for processing eight is modified konjac glucomannan, and the film forming agent used for processing nine is konjac glucomannan; FIG. 1 shows that the modified konjac glucomannan has better fresh-keeping effect. The reason for this is probably that the modified konjac glucomannan is beneficial to the mutual crosslinking of intermolecular hydroxyl hydrogen bonds after acetyl groups on konjac glucomannan molecules are removed, the film forming toughness is enhanced, and the film forming performance is better.

In conclusion, in the nine treatment modes, when the coating liquid consists of 0.05 percent of phytic acid, 2g/L of chlorine dioxide and 0.3 percent of modified konjac glucomannan, the fresh-keeping of the okra is facilitated. On day 9 of storage, the chlorophyll of the uncoated group remained only 36% and the complex preservative chlorophyll 90%.

Experiment II influence of punching time of freshness protection package on chlorophyll content of okra

The experimental fresh-keeping coating liquid contains 0.05 percent of phytic acid, 2g/L of chlorine dioxide and 2g/L of modified konjac glucomannan. The okra coated with the preservative film coating solution is randomly divided into 7 bags, and each bag is filled with 20 okra strips. The first bag was used as a control, and the remaining six bags were subjected to pricking treatment after days 1, 2, 3, 4, 5, and 6, respectively. Storing at normal temperature, and detecting chlorophyll once every 2 days. If the task of puncturing the hole is available in the same day, the sample is firstly measured and then the hole is punctured on the freshness protection package. The results of the experiment are shown in FIG. 2.

As can be seen from FIG. 2, the chlorophyll dropping speed is slowest in the 3 rd day of the time of punching the holes in the freshness protection package, so that the color of the okra can be well maintained. According to the chlorophyll content and the speed reduction trend of each storage time shown in fig. 2, the fresh-keeping effect of pricking holes on the 1 st day and the 2 nd day is slightly lower than that of a group without pricking holes, which indicates that the pricking time is too early. The puncturing groups on the 4 th day, the 5 th day and the 6 th day have better chlorophyll preservation results than the non-puncturing groups in the following days, but the puncturing time is worse than the puncturing group on the 3 rd day, and the effect is obviously worse. The reason for this may be that the physiological activities such as respiration are still going on after the okra is picked up, and the proper concentration of O is kept in the fresh-keeping bag₂、CO₂Gases such as water vapor can slow down the maturation-aging-spoilage process. In the early stage of sealing, okra breathes vigorously in the bag and O in the bag₂Rapid decrease of content, CO₂The concentration is increased, and the spontaneous regulation inhibits the respiratory metabolism. And after the fresh-keeping bag is punctured in a later period, the air permeability and the moisture permeability of the fresh-keeping bag can be effectively changed, the accumulation of volatile substances such as ethanol and acetaldehyde caused by too low oxygen concentration is slowed down, and the quality is reduced. In a word, the fresh-keeping effect of the MA natural atmosphere and the fresh-keeping bag by timely puncturing the holes after the okra is coated with the film is better than that of the simple MA natural atmosphere, the chlorophyll is best kept when the fresh-keeping bag is punctured on the 3 rd day, and the chlorophyll is about 6% higher than that of the un-punctured hole group in the composite fresh-keeping on the 8 th day of the storage period.

Experiment on influence of immersion time of okra in fresh-keeping coating liquid on chlorophyll content

Taking the uncoated okra as a reference, soaking the okra in a fresh coating solution (containing phytic acid 0.05%, chlorine dioxide 2g/L and modified konjac glucomannan 0.3%) for 10s, 30s, 1min, 1.5min, 2min and 2.5min, airing, then placing in a fresh-keeping bag for storage, pricking holes in the bag on the 3 rd day (the same below), and measuring the chlorophyll content in the 0 th, 3 rd, 6 th, 9 th, 12 th and 15 th days respectively, wherein the experimental result is shown in figure 3.

As can be seen from fig. 3, the chlorophyll content of each group decreased from the beginning of storage. But compared with the control group, the chlorophyll is degraded slowly when the immersion time is 1-2min, and particularly the chlorophyll is reduced at the slowest when the immersion time is 1 min; the chlorophyll content can still reach about 80% of the initial amount by day 15, so the membrane liquid immersion time is selected to be 1 min.

Experiment four effects of component concentration of fresh-keeping coating solution on okra cellulose content

Carrying out an L9(33) orthogonal experiment according to the table 1 by using three factors of phytic acid concentration, chlorine dioxide concentration and modified konjac glucomannan concentration in the fresh-keeping coating liquid to obtain the coating liquid which is formed by the experiment numbers 1-9 in the table 2.

Table 1: orthogonal test factor level of film coating liquid concentration

The okra was randomly packed into freshness protection bags, 20 per bag, for a total of 9 bags. And (3) coating each bag of okra with a coating liquid corresponding to test numbers of 1-9 respectively, and naturally airing. And (3) storing at normal temperature, pricking the freshness protection packages on the 3 rd day, and detecting the content of the okra cellulose in each freshness protection package on the 8 th day, wherein the experimental results are shown in table 2.

Table 2: orthogonal test factor level of film coating liquid concentration

Test No	A	B	C	Cellulose content (%)
					1	1	1	1	1.42
2	2	2	2	0.50
					3	3	3	3	0.64
4	1	2	3	0.82
					5	2	3	1	1.05
6	3	1	2	1.14
					7	1	3	2	0.95
8	2	1	3	1.21
					9	3	2	1	1.10
k1	1.06	1.26	1.19
					k2	0.91	0.79	0.85
k3	0.96	0.88	0.89
					R	0.15	0.47	0.34

The higher the content of the okra cellulose is, the poorer the edibility is, and the higher the okra cellulose content is, the important index reflecting the fresh-keeping effect and edibility of the okra. The cellulose content of the just picked okra is determined to be 0.32%. As can be seen from table 2, the combination most effective in inhibiting cellulose increase was A2B2C2, i.e. phytic acid concentration was 0.05%, chlorine dioxide concentration was 2g/L, modified konjac glucomannan concentration was 0.3%, and the cellulose content at day 8 was only 0.52%, only 60% increase at this combination. According to the range data, the influence sequence of all factors is as follows: b (chlorine dioxide concentration) > C (modified konjac glucomannan concentration) > A (phytic acid concentration).

Experiment six optimizes the influence of coating on the quality of okra under the preservation parameter

Taking the uncoated okra as a control, soaking the okra in a fresh-keeping coating solution (containing 0.05% of phytic acid, 2g/L of chlorine dioxide and 0.3% of modified konjac glucomannan) for 1min, naturally drying the okra, filling the okra into a fresh-keeping bag, pricking the bag on the 3 rd day, checking the okra at intervals of 3-4 days, and calculating the commodity rate. Meanwhile, the content of chlorophyll, cellulose, Vc and MDA is respectively measured by selecting the okra with commercial property at the time. The experimental results are shown in FIGS. 4-8.

As can be seen from fig. 4: the chlorophyll content of film coated group of flos Abelmoschi Manihot is reduced remarkably slowly, and the chlorophyll content of 19 days of storage is 0.095mg.g^-115 times that of the uncoated film group; the coating treatment can inhibit the degradation of okra chlorophyll.

As can be seen from fig. 5: the speed of the cellulose content of the okra in the film coating group is obviously and slowly increased, the cellulose content in the film coating group stored on the 19 th day is 0.72 percent and is less than 30 percent of that in the film coating group; the coating treatment was shown to be effective in inhibiting the fibrosis of okra.

As can be seen from fig. 6: the decrease of the Vc content of the okra in the coated group is obviously slow, and the Vc is still kept 61% on the 19 th day of storage and is more than 4 times of that in the uncoated group (the Vc of the uncoated control group is only kept about 13%). The coating treatment can prevent oxygen from entering cells to a certain degree, inhibit the activity of the ascorbate enzyme and slow down the degradation of the okra Vc.

As can be seen from fig. 7, MDA increased with the increase of storage time of okra. The MDA acceleration for the coated group was significantly slower compared to the uncoated group. The MDA content of the coating group at day 19 was only 59% of that of the control group; the components of the film coating liquid delay the oxidation of the cell membrane lipid of the okra and maintain the physiological function of the picked okra membrane to a certain extent.

As can be seen from fig. 8: the okra commercial rate for the coated group decreased significantly more slowly with shelf life than for the uncoated group. The commercial yield of the coated film group at day 19 can still reach 80 percent, which is 8 times that of the uncoated film group.