CN108450966B

CN108450966B - Efficient bitter almond peeling method

Info

Publication number: CN108450966B
Application number: CN201810189766.7A
Authority: CN
Inventors: 张清安; 吴东栋; 黄小丽
Original assignee: Shaanxi Normal University
Current assignee: XINJIANG DADEHENG BIOLOGY CO.,LTD.
Priority date: 2018-03-08
Filing date: 2018-03-08
Publication date: 2020-02-14
Anticipated expiration: 2038-03-08
Also published as: CN108450966A

Abstract

The invention relates to a method for peeling bitter almonds with high efficiency by using superheated steam technology, which peels the bitter almonds by using superheated steam technology, carries out pre-freezing treatment on the bitter almonds, then carries out quick rinsing on the bitter almonds by using water to remove dust and impurities on the surfaces of the bitter almonds, then carries out superheated steam treatment, takes out the bitter almonds and rolls the bitter almonds into two halves by using a peeling machine, thereby realizing the purpose of quick and low-emission peeling, the invention adopts the superheated steam, the skins of the bitter almonds are burst in temperature rise in the environment with high humidity and high temperature, which is beneficial to realizing skin and kernel separation in the later rolling, the temperature and the pressure of the superheated steam present a one-to-one correspondence relationship, the temperature of the superheated steam can be changed by reducing the pressure, the saturation temperature of the steam can be reduced by reducing the pressure, thereby obtaining better peeling effect, reducing the loss of effective components, is beneficial to the development and utilization of the skin in the later period.

Description

Efficient bitter almond peeling method

Technical Field

The invention belongs to the technical field of bitter almond processing and particularly relates to a bitter almond efficient peeling method.

Background

The almond is dried seed of apricot, and has flat heart shape, and reddish brown or dark yellow seed coat. The almonds are rich in nutrition, each hundred grams of almonds contain 23-27 g of protein, 50-60 g of crude fat and 10g of sugar, and also contain inorganic salts such as calcium, phosphorus, iron, potassium, selenium and the like and a plurality of vitamins such as riboflavin, nicotinic acid, ascorbic acid and the like, so that the almond is a good tonic.

Meanwhile, as about 3 percent of amygdalin is contained in the bitter almond, the amygdalin can be decomposed (hydrolyzed) under the action of β -glucosaccharase coexisting with the amygdalin to generate benzaldehyde and hydrocyanic acid, the benzaldehyde has special fragrance and is a flavor substance in the almond product, the hydrocyanic acid belongs to a highly toxic substance and cannot be directly eaten, the amygdalin must be removed firstly, and in order to ensure that the amygdalin can be smoothly migrated from the bitter almond so as to shorten the debittering time, red seed coats (almond skins, the content of which accounts for about 2 to 5 percent of the almond) of the bitter almond are removed before the debittering.

In industrial production, hot water blanching (95-100 ℃ for 5-40 minutes) or alkali liquor is mostly used for peeling bitter almonds, and then the treated bitter almonds are sent to a peeling machine to be kneaded and peeled. The peeling method has the following disadvantages: on one hand, the water consumption is large (the ratio of material to liquid is 1: 8-1: 20), the waste water discharge is large, and the environmental pollution is serious; on the other hand, the blanching treatment also causes the change and loss of the almond hull structure and the nutrient components. Namely, under the condition of industrial hot blanching treatment, particularly adding chemical reagents such as sodium hydroxide and the like, functional components such as polyphenol, flavone, dietary fiber, amygdalin and the like in almond peel can be largely lost and transferred into peeled water, so that the original valuable functional components of food are changed into waste, organic matters in the peeled water exceed the standard, the environment is seriously polluted after the discharge, and resources are wasted; meanwhile, the discharge of such polluted water is also strictly prohibited by environmental protection departments. The situation seriously restricts the development of the bitter almond processing industry and needs to be solved urgently.

Researches show that the bitter almond skin not only contains components such as protein, pectin, flavone, polyphenol and the like, but also contains a large amount of dietary fibers such as starch, hemicellulose, cellulose, lignin and the like, and has good application and development prospects. In foreign countries, almond hulls are not only used as animal feed, but also as a biological energy source. But the cases of domestic development and utilization are few. The traditional peeling with boiling water and alkali liquor results in low preservation rate of nutrient components in the peel, serious pollution of peeling water and serious color browning of peeled almonds. Therefore, how to adopt the modern food green processing technology to replace the traditional boiling water blanching, and simultaneously reducing the loss of nutrient components in the skin and the discharge of waste water becomes the bottleneck to be overcome in the bitter almond processing industry.

Disclosure of Invention

In order to overcome the defects of the existing bitter almond processing technology, the invention provides the bitter almond efficient peeling method which has the advantages of high peeling rate, short peeling time, less loss of effective nutrition, less water consumption, capability of keeping the integrity of the peel and contribution to the development and utilization of the peel in the later period.

The technical scheme adopted by the invention is as follows:

an efficient bitter almond peeling method comprises the following steps:

(1) screening bitter almonds, removing moldy bitter almonds with incomplete surfaces, and pre-freezing the screened bitter almonds in a low-temperature environment of-40-0 ℃ for a period of time;

(2) placing the pre-frozen bitter almonds into a screen container, putting the bitter almonds and the container into water, and leaching the screen container filled with the bitter almonds in the water up and down at the temperature of 20-50 ℃ for 3-60 min;

(3) draining the leached bitter apricot kernels, placing the bitter apricot kernels in a treatment chamber for superheated steam treatment, and controlling the temperature of the superheated steam by adjusting the pressure intensity to enable the bitter apricot kernels to be rapidly cracked and removed in a high-temperature high-humidity superheated steam environment after the bitter apricot kernels are swelled;

(4) transferring the bitter apricot kernels treated by superheated steam into a peeling machine for kneading and peeling.

Further limiting, the pre-freezing treatment in the step (1) is 0.5-3 h.

And (3) further limiting, wherein the water consumption for leaching in the step (2) is 0.5-4 times of the weight of the bitter apricot seeds.

Further defined, the superheated steam treatment conditions of the step (3) are as follows: the steam temperature is controlled to be 60-170 ℃, the pressure is 0.02-0.25 MPa, the treatment time is 2-20 min, the relative humidity is 60-100%, and the wind speed is 1-5 m/s.

More specifically, the superheated steam treatment conditions in the step (3) are as follows: the steam temperature is controlled to be 80-100 ℃, the pressure is 0.04-0.1 MPa, the treatment time is 2-5 min, the relative humidity is 85%, and the wind speed is 1.5-2 m/s.

The invention relates to a method for efficiently peeling bitter almonds, which is characterized in that the bitter almonds are peeled by using a superheated steam technology, the bitter almonds are quickly leached by using water after being pre-frozen to remove dust and impurities on the surfaces of the bitter almonds, then the bitter almonds are treated by superheated steam, and are taken out and rolled into two halves by using a peeling machine, so that the aim of quick and low-emission peeling is fulfilled. Compared with the prior art, the invention has the beneficial effects that:

(1) compared with the traditional hot water scalding method (95-100 ℃) for peeling, the water for washing the almonds is room-temperature water and is short in time, so that on one hand, dust, impurities and the like on the surfaces of the almonds are removed, and a foundation can be laid for the subsequent utilization of the removed almond peels; on the other hand, the bitter almond peel washing with water can also have the effect of swelling the bitter almond peel so as to be easy to burst and remove, and the pigment substances in the bitter almond peel are hardly transferred into the peeling water after washing, so that the dissolution of effective components in the traditional peeling process is reduced; in addition, the peeling water can be repeatedly used, the water consumption is about 0.5-4 times of the weight of the bitter apricot kernels, a large amount of water can be saved, and meanwhile, the sewage discharge is reduced. In addition, since water is not required to be heated to raise the temperature, the heat energy consumption is reduced.

(2) In the invention, superheated steam is adopted to form a high-humidity high-temperature environment in the peeling process of the bitter almonds, so that the skins of the bitter almonds in the bitter almonds are cracked in the heating process, thereby being beneficial to realizing skin and kernel separation in the later rolling process. In addition, the temperature and the pressure of the superheated steam are in one-to-one correspondence, the temperature of the superheated steam can be changed by reducing the pressure, namely, the saturation temperature of the superheated steam can be reduced (namely, the pressure of the superheated steam can be high or low) by reducing the pressure, and a better peeling effect is achieved; meanwhile, the loss of active ingredients in the peel by high-temperature water in the traditional peeling process is reduced, the nutritional value of the almond peel is greatly reserved, and the almond peel obtained after peeling is complete and convenient to recover and store, so that the peel is beneficial to later development and utilization.

(3) Compared with saturated steam, superheated steam has the advantages that water molecules move more violently, the superheated steam has two properties of heating and drying substances like hot air and condensing into water when contacting substances with the temperature far lower than the temperature of the saturated steam, the superheated steam has low net energy consumption and excellent heat conductivity, and has the characteristics of rapid drying, short time and energy recycling.

(4) By using superheated steam for peeling, β -glucosaccharase and polyphenol oxidase in the bitter almond can be more effectively passivated compared with the traditional peeling, so that the color change of enzymatic browning and the like caused by the polyphenol oxidase in the processing processes of peeling, later drying and the like of the bitter almond is reduced, the enzymolysis of the amygdalin in the debittering process can be reduced, the content of the amygdalin in the debittered water is increased, and a foundation is provided for effectively developing and utilizing the amygdalin in the debittered water.

Drawings

FIG. 1 is a comparison of different peeling patterns versus weight loss of almonds.

FIG. 2 is a comparison of water usage for different peeling modes.

FIG. 3 is a graph showing the effect of different peeling patterns on peeling time.

FIG. 4 is a graph showing the effect of different peeling patterns on the rate of polyphenol loss.

FIG. 5 is a graph of the effect of different peeling patterns on peeled water color values.

FIG. 6 shows the effect of different desquamation methods on enzyme activity loss.

FIG. 7 is a graph showing the effect of different peeling patterns on peeling rate.

Detailed Description

The technical scheme of the invention is further explained by combining the drawings and experiments.

The invention relates to a bitter almond efficient peeling method, which comprises the following process flows:

selecting bitter almond, removing impurities → pre-freezing treatment → leaching → superheated steam treatment → kneading and peeling

According to the process flow, the peeling of the bitter almonds is realized by the following method:

(1) screening bitter almonds, selecting the bitter almonds with better appearance and complete granules, removing the bitter almonds with mildewed and incomplete surfaces, and pre-freezing the screened bitter almonds for a period of time at the low temperature of between 40 ℃ below zero and 0 ℃;

(2) placing the pre-frozen bitter almonds into a screen container with grid gaps, putting the bitter almonds and the container into water, and enabling the screen container containing the bitter almonds to be leached up and down in the water, wherein the amount of the water is ensured to be enough to immerse the bitter almonds, and the water temperature is between 20 and 50 ℃ and the time is 3 to 60 minutes;

(3) draining the leached bitter apricot kernels, placing the bitter apricot kernels in a treatment chamber for superheated steam treatment, and controlling the temperature of the superheated steam by adjusting the pressure intensity to enable the bitter apricot kernels to swell and then burst and fall off in a high-temperature high-humidity superheated steam environment; the steam temperature is controlled to be 60-170 ℃, the pressure is 0.02-0.25 MPa, the treatment time is 2-20 min, the relative humidity is 60-100%, and the wind speed is 1-5 m/s.

The process conditions used for each example are shown in table 1 below:

TABLE 1 Process conditions used in the examples

In order to verify the technical effect of the invention, the peeling method of the invention is compared with the traditional hot water blanching method, and the specific experiment is as follows:

the traditional hot water blanching method comprises the following steps: soaking the bitter apricot seeds in boiling water at the temperature of 95-100 ℃ for 5-40 minutes.

(1) Loss of weight

The weight loss after peeling was calculated by comparing the weight of the almonds before and after peeling, and the results are shown in fig. 1.

As can be seen from figure 1, the quality of the bitter almond is lost by 7% after the bitter almond is peeled by the traditional hot water blanching method (boiling water is 95-100 ℃, and the peeling time is 5min), while the bitter almond is only lost by about 0.5% after being peeled by the superheated steam treatment method of the invention.

(2) Water demand

The water consumption in the peeling process of the traditional hot water blanching method is compared with the water consumption of the invention, and the result is shown in figure 2.

As can be seen from FIG. 2, the water amount required for peeling by the traditional hot water blanching method is about 7 times of the weight of the bitter apricot kernels, and the water amount required for peeling by the superheated steam is only 0.8 times of the weight of the bitter apricot kernels; the difference between the water discharge amount and the water discharge amount is very large, and because the pigment substances in the bitter almond peels are hardly transferred into the peeling water after being washed, and the water for washing the bitter almonds can be repeatedly used, the superheated steam peeling method has almost no waste water discharge.

(3) Peeling time

The bitter apricot kernels are directly treated by superheated steam after being pre-frozen, the peeling time of the bitter apricot kernels is recorded and compared with the peeling time of the bitter apricot kernels after being pre-frozen, leached and treated by superheated steam, and the result is shown in figure 3.

As can be seen from fig. 3, the peeling time can be shortened from 8min to 3min through the leaching pretreatment, and the advantage of the leaching pretreatment before the peeling of the superheated steam is fully embodied.

(4) Loss rate of polyphenols

The results of comparing the polyphenol loss rate after peeling by the conventional hot water blanching method with the polyphenol loss rate after directly performing superheated steam treatment on bitter apricot kernels after pre-freezing treatment and the polyphenol loss rate after pre-freezing, leaching and superheated steam treatment according to the invention are shown in fig. 4.

As can be seen from FIG. 4, the pre-freezing, the leaching and the superheated steam treatment of the invention can generate a synergistic effect, and compared with the traditional hot water blanching method, the invention can greatly reduce the loss of polyphenols in the skins.

(5) Color value of water for peeling

The color values of the de-skinned water from the conventional hot water blanching process were compared to the color values of the rinse water used after the pre-freezing, rinsing and superheated steam treatment of the present invention, and the results are shown in fig. 5.

As can be seen from FIG. 5, the water used for the superheated steam peeling had a lighter color with less red and yellow values, consistent with the loss of polyphenols in FIG. 4.

(6) Loss of enzyme activity

Comparing the activity loss of β -glucosidase and polyphenol oxidase in the bitter apricot seeds treated by the traditional hot water blanching method with the activity loss of β -glucosidase and polyphenol oxidase in the bitter apricot seeds treated by pre-freezing, rinsing and superheated steam, the result is shown in fig. 6.

As can be seen from figure 6, the pre-freezing, leaching and superheated steam treatment of the invention have large activity loss on β -glucosidase and polyphenol oxidase, which lays a foundation for ensuring stable quality of bitter almond in the later processing processes of debitterizing, drying and the like.

(7) Peeling rate

Comparing the peeling rate of the bitter apricot kernels treated by the traditional hot water blanching method with the peeling rate of the pre-freezing, rinsing and superheated steam treatment of the present invention, the result is shown in fig. 7.

As can be seen from the figure 7, the peeling rate of the pre-freezing, rinsing and superheated steam treatment is slightly higher than that of the conventional hot water blanching, and meanwhile, the method can reduce the waste water discharge and the influence on the quality of the almond color and the like.

Through the experimental comparison, the invention can greatly reduce the waste water discharge on the basis of ensuring the same peeling rate as the traditional hot water blanching method, has less loss on the quality, color, nutrition and the like of peeled bitter almonds, greatly ensures the small loss of the nutrition of the bitter almond peels, and does not influence the later development and utilization of the peels.

Claims

1. An efficient bitter almond peeling method is characterized by comprising the following steps:

(3) draining the leached bitter apricot kernels, placing the bitter apricot kernels in a treatment chamber for superheated steam treatment, and controlling the temperature of the superheated steam by adjusting the pressure intensity to enable the bitter apricot kernels to be rapidly cracked and removed in a high-temperature high-humidity superheated steam environment after the bitter apricot kernels are swelled; the superheated steam treatment conditions were: controlling the steam temperature to be 60-170 ℃, the pressure to be 0.02-0.25 MPa, the treatment time to be 2-20 min, the relative humidity to be 60-100% and the wind speed to be 1-5 m/s;

2. The method for efficiently peeling bitter almonds according to claim 1, wherein the method comprises the following steps: the pre-freezing treatment in the step (1) is carried out for 0.5-3 h.

3. The method for efficiently peeling bitter almonds according to claim 1, wherein the method comprises the following steps: the water consumption for leaching in the step (2) is 0.5-4 times of the weight of the bitter apricot seeds.

4. The method for efficiently peeling bitter almonds according to claim 1, wherein the method comprises the following steps: the superheated steam treatment conditions of the step (3) are as follows: the steam temperature is controlled to be 80-100 ℃, the pressure is 0.04-0.1 MPa, the treatment time is 2-5 min, the relative humidity is 85%, and the wind speed is 1.5-2 m/s.