CN113558202A - Preparation method of sulfur-free and brown stain-free konjac dry slices - Google Patents

Preparation method of sulfur-free and brown stain-free konjac dry slices Download PDF

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CN113558202A
CN113558202A CN202110641013.7A CN202110641013A CN113558202A CN 113558202 A CN113558202 A CN 113558202A CN 202110641013 A CN202110641013 A CN 202110641013A CN 113558202 A CN113558202 A CN 113558202A
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konjac
free
microwave
slices
pieces
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CN113558202B (en
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李秉正
黄纪民
黄志民
吴钊龙
陈先锐
胡文进
师德强
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Guangxi Zhongke Microwave Advanced Manufacturing Industry Technology Research Institute
Nanning Zhongke Microwave Advanced Manufacturing Industry Technology Research Institute
Guangxi Academy of Sciences
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Guangxi Zhongke Microwave Advanced Manufacturing Industry Technology Research Institute
Nanning Zhongke Microwave Advanced Manufacturing Industry Technology Research Institute
Guangxi Academy of Sciences
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    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L19/00—Products from fruits or vegetables; Preparation or treatment thereof
    • A23L19/10—Products from fruits or vegetables; Preparation or treatment thereof of tuberous or like starch containing root crops
    • A23L19/115—Konjak; Konntaku
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
    • A23L5/20—Removal of unwanted matter, e.g. deodorisation or detoxification
    • A23L5/21—Removal of unwanted matter, e.g. deodorisation or detoxification by heating without chemical treatment, e.g. steam treatment, cooking
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
    • A23L5/20—Removal of unwanted matter, e.g. deodorisation or detoxification
    • A23L5/27—Removal of unwanted matter, e.g. deodorisation or detoxification by chemical treatment, by adsorption or by absorption
    • A23L5/276—Treatment with inorganic compounds
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
    • A23L5/30—Physical treatment, e.g. electrical or magnetic means, wave energy or irradiation
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
    • A23L5/30—Physical treatment, e.g. electrical or magnetic means, wave energy or irradiation
    • A23L5/34—Physical treatment, e.g. electrical or magnetic means, wave energy or irradiation using microwaves
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
    • A23L5/40—Colouring or decolouring of foods
    • A23L5/41—Retaining or modifying natural colour by use of additives, e.g. optical brighteners
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
    • A23V2002/00—Food compositions, function of food ingredients or processes for food or foodstuffs
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
    • Y02P60/80—Food processing, e.g. use of renewable energies or variable speed drives in handling, conveying or stacking
    • Y02P60/85—Food storage or conservation, e.g. cooling or drying

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Abstract

The invention discloses a preparation method of sulfur-free and brown stain-free dry konjac slices, which comprises the steps of removing soil from fresh konjac, washing the fresh konjac, heating the konjac in a microwave drying box, peeling the konjac, cutting off surface pulp, slicing, putting the konjac into an ozone sterilizer for ozone fumigation, irradiating the konjac for 20-30 min under ultraviolet light, drying the konjac for 60-80 min by microwave, and reducing the final wet base water content of the dry konjac slices to below 8% to obtain the sulfur-free and brown stain-free dry konjac slices. The method has no sulfur fumigation color, maintains the color of the konjak, effectively reduces the nutrition loss of the konjak, improves the production efficiency, solves the problems of brown stain, poor quality and the like in the process of drying the konjak slices, and realizes the deep processing comprehensive utilization of the konjak raw material.

Description

Preparation method of sulfur-free and brown stain-free konjac dry slices
Technical Field
The invention belongs to the field of agricultural product processing technology, and particularly relates to a preparation method of a sulfur-free and browning-free konjac dry tablet.
Background
The konjac is also named as konjac and coprinus konjac, belongs to the genus konjac of the family Araceae, is an important plant resource in China, has important medicinal, edible and industrial values, and is the only economic plant containing glucomannan. The glucan is a high molecular weight non-ionic polysaccharide, an excellent dietary fiber, called a seventh nutrient, and is a health food in the new century. Has effects in reducing blood lipid, blood glucose and cholesterol, regulating endocrine, and preventing obesity. However, because konjak contains a large amount of polyphenol substances and polyphenol oxidase, the polyphenol oxidase can oxidize the polyphenol substances under the action of oxygen in the air to generate brown pigment, so that konjak slices are blackened, the content of glucomannan is seriously reduced, the whiteness grade of the konjak slices and deep-processed products (such as konjak coarse powder, konjak gum and the like) is influenced, and the color and the appearance of the konjak powder are influenced. The browning of the konjac can occur to a certain degree after the konjac is sliced, so that the enzyme deactivation treatment needs to be carried out quickly, and the main problem of the fresh konjac drying processing is how to control the browning of the konjac. Generally, in order to prevent browning, the konjac is generally subjected to sulfur fumigation for color protection when being dried, and sulfur-fumigated konjac slices can keep the konjac white, but in the sulfur fumigation process, the sulfur content is difficult to control, and the konjac slices are difficult to remove at a later stage, so that potential safety hazards such as excessive sulfur content exist, the existing method is difficult to meet the requirements of development of the konjac industry, and a new processing technology is urgently required to be developed to further process the konjac, so that the added value of products is further improved.
Disclosure of Invention
Aiming at the defects, the invention discloses a preparation method of a sulfur-free and browning-free konjac dry slice, which solves the problems of browning, poor quality and the like in the konjac slice drying process and realizes the deep processing comprehensive utilization of konjac raw materials.
The invention is realized by adopting the following technical scheme:
a preparation method of sulfur-free and browning-free konjak dry slices comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 7-10 KW, and the heating time is 27-52 s;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 4.5-5.5 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 2-5 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, and fumigating with ozone for 20-30 min under the condition that the concentration value of ozone is 450-550 PPM;
(6) ultraviolet irradiation: placing the konjac slices treated in the step (5) under ultraviolet light for irradiating for 20-30 min, wherein the ultraviolet light intensity is 0.5-1.5 mW/cm2；
(7) Microwave drying: and (4) microwave drying the konjac pieces processed in the step (6), wherein the microwave frequency is 2450MHz, the microwave power is 0.2-1.5 kW, and the microwave drying time is 60-80 min, so that the final wet basis water content of the konjac pieces is reduced to below 8%, and sulfur-free low-browning konjac dry pieces are obtained and stored after nitrogen-filled packaging.
Further, the heating temperature in the step (1) is 63.7-74.8 ℃.
Further, in the ozone fumigation step, the spreading density of the konjac pieces0.4 to 0.6g/cm2。
Further, in the ultraviolet irradiation step, the paving density of the konjac pieces is 0.4-0.6 g/cm2. The spreading density is controlled, so that the uniform irradiation of ultraviolet rays on the konjac pieces is guaranteed, and the ultraviolet irradiation effect is improved.
Further, in the microwave drying step, the paving density of the konjac pieces is 0.4-0.6 g/cm2. The paving density is strictly controlled, because the larger the paving density is, the smaller the evaporation amount of the moisture of the material is, and the drying efficiency is slow.
Further, in the step (7), the konjac pieces are subjected to microwave drying treatment in two sections, firstly, the konjac pieces are continuously heated for 1-3 min under the conditions that the microwave power is 1.0kW and the microwave frequency is 2450MHz, so that the konjac pieces are quickly heated to the drying temperature, and then the konjac pieces are continuously heated for 60-80 min under the conditions that the microwave power is 0.3kW and the microwave frequency is 2450MHz, so that the final moisture content of the wet base of the konjac dry pieces is reduced to below 8%. The konjac pieces are subjected to microwave drying treatment in two sections, the temperature of the konjac pieces is quickly increased by using higher microwave power in the early stage, evaporation of a large amount of water is accelerated, and the water is uniformly distributed in the konjac pieces again by using lower microwave power in the later stage, so that local coking caused by overheating is avoided.
Further, the temperature of the microwave drying in the step (7) is 65-75 ℃.
Compared with the prior art, the technical scheme has the following beneficial effects:
1. the traditional konjak drying generates heat by burning wood and coal, the drying time is long, the energy consumption is large, the quality after drying is not high, the environment is seriously polluted, the domestic industrial product of the dried konjak product is dried by a hot air drying oven at present, although the efficiency is improved compared with the traditional processing method, the color and luster of the konjak piece are poor in appearance and quality, and the loss of nutritional ingredients is more.
The technology of the invention integrates microwave, ozone and ultraviolet technology, compared with the crisp chips prepared by the traditional technology, the dried product has certain improvement on nutrition and crispness, uniform color and luster, excellent quality, no special requirement on drying equipment, low investment cost, simple technology, no waste water and convenient popularization and application.
2. According to the invention, a treatment method combining microwave irradiation and ozone fumigation is adopted, browning of konjak can be effectively inhibited, firstly, polyphenol oxidase passivation is carried out on konjak bulbs on the premise of not peeling by utilizing the high penetrability of 915MHz microwave, then secondary enzyme inactivation is carried out on sliced konjak slices by utilizing ozone fumigation, the obtained enzyme inactivation effect is good, and then the konjak slice product without sulfur, other chemical color fixative residues and high whiteness can be obtained by drying. Because of the unique heating characteristic and drying mechanism of microwave drying, microwave heating is an ideal method for sterilizing and inactivating enzyme, and 915MHz microwave has larger working frequency penetrating depth of materials compared with 2450MHz microwave, and can process thicker and larger materials. The microwave heating has the characteristics of high heating speed, small heat loss, convenient operation and the like, can shorten the process time, improve the productivity, reduce the cost, improve the product quality, heat the inside and the outside of the material simultaneously, can obtain better enzyme killing effect compared with the traditional method, can better keep the original color, aroma and taste of the material, has less loss of nutrient components, has natural color and luster and attractive appearance of the dried product, has better drying quality, and can obviously improve the drying speed and reduce the energy consumption.
3. The surface layer of the peeled konnyaku is cut to a certain thickness because the pulp near the surface layer is easily blackened in the drying process. Moreover, because the konjac contains a large amount of polyphenol substances and polyphenol oxidase, the thickness of the konjac slices needs to be strictly controlled in the drying process, and if the slice thickness is too small, the drying speed is too high, so that the konjac slices are locally overheated to form scorch; the slice thickness is too large, the drying rate is slow, the drying degree of each part is uneven, and the interior is easy to overheat to cause blackening.
Detailed Description
The invention is further illustrated by the following examples, which are not to be construed as limiting the invention thereto. The following examples are given without reference to specific experimental conditions and methods, which are generally conventional and well known to those skilled in the art, wherein the color of the dried konjac pieces is measured using a CR-400 type color difference meter, using a standard ceramic white board as a standard, using the CIE L a b uniform color space color system, and L is the brightness of the color; a is red-green chroma, a is "+" represents red, and a is "-" represents green; b is the shade of yellow and blue, b is "+" representing yellow, and b is "-" representing blue. In the measurement process of the specific example, the L value of the chroma is adopted, and if the L value is larger, the whiteness of the dry konjac pieces is high.
Example 1:
a preparation method of sulfur-free and browning-free konjak dry slices comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 8KW, the heating time is 52s, and the heating temperature is 68.5 ℃;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 5.0 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 4 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, fumigating the konjac slices with ozone for 30min under the condition that the ozone concentration value is 450-550 PPM, wherein the spreading density of the konjac slices is 0.45g/cm2；
(6) Ultraviolet irradiation: irradiating the konjac slices treated in the step (5) for 30min under ultraviolet light, wherein the paving density of the konjac slices is 0.55g/cm2Ultraviolet light intensity of 1.5mW/cm2；
(7) Microwave drying: the konjac slices treated in the step (6) are subjected to microwave drying treatment in two sections, the temperature of the microwave drying is 70 ℃, and the paving density of the konjac slices is 0.45g/cm2Firstly, continuously heating for 3min under the conditions that the microwave power is 1.0kW and the microwave frequency is 2450MHz to quickly heat the konjac pieces to the drying temperature, and then continuously heating for 75min under the conditions that the microwave power is 0.3kW and the microwave frequency is 2450MHz to finally make the konjac dry pieces wet-based hydrousReducing the content to below 8 percent to obtain the sulfur-free low-browning konjac dry slices, and then filling nitrogen to package and store the konjac dry slices.
The final wet basis water content of the obtained dry konjac slice is 6.55%, L is 84.44, and the dry konjac slice has uniform color and no color difference.
Example 2:
a preparation method of sulfur-free and browning-free konjak dry slices comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 9KW, the heating time is 52s, and the heating temperature is 65.4 ℃;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 4.8 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 3 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, fumigating the konjac slices with ozone for 25min under the condition that the ozone concentration value is 450-550 PPM, wherein the paving density of the konjac slices is 0.5g/cm2；
(6) Ultraviolet irradiation: irradiating the konjac slices treated in the step (5) for 25min under ultraviolet light, wherein the paving density of the konjac slices is 0.55g/cm2The ultraviolet light intensity is 0.5-1.5 mW/cm2；
(7) Microwave drying: the konjac slices treated in the step (6) are subjected to microwave drying treatment in two sections, the temperature of the microwave drying is 68 ℃, and the paving density of the konjac slices is 0.5g/cm2Firstly, continuously heating for 2min under the conditions that the microwave power is 1.0kW and the microwave frequency is 2450MHz to quickly heat the konjac pieces to the drying temperature, then continuously heating for 60-80 min under the conditions that the microwave power is 0.3kW and the microwave frequency is 2450MHz to reduce the final wet-based water content of the konjac dry pieces to below 8 percent to obtain sulfur-free low-browning konjac dry pieces, and then filling nitrogen for packaging and storing.
The final wet basis water content of the obtained dry konjac pieces is 6.82%, L is 84.32, and the dry konjac pieces are uniform in color and free of color difference.
Example 3:
a preparation method of sulfur-free and browning-free konjak dry slices comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 10KW, the heating time is 27s, and the heating temperature is 74.8 ℃;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 5.2 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 2 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, fumigating with ozone for 20min under the condition that the ozone concentration value is 450-550 PPM, wherein the spreading density of the konjac slices is 0.4g/cm2；
(6) Ultraviolet irradiation: irradiating the konjac slices treated in the step (5) for 20min under ultraviolet light, wherein the paving density of the konjac slices is 0.6g/cm2Ultraviolet light intensity of 0.7mW/cm2；
(7) Microwave drying: the konjac slices treated in the step (6) are subjected to microwave drying treatment in two sections, the temperature of the microwave drying is 72 ℃, and the paving density of the konjac slices is 0.5g/cm2Firstly, continuously heating for 2min under the conditions that the microwave power is 1.0kW and the microwave frequency is 2450MHz to quickly heat the konjac pieces to the drying temperature, then continuously heating for 80min under the conditions that the microwave power is 0.3kW and the microwave frequency is 2450MHz to reduce the final wet-based water content of the konjac dry pieces to below 8 percent to obtain the sulfur-free low-browning konjac dry pieces, and then filling nitrogen to package and store the sulfur-free low-browning konjac dry pieces.
The final wet basis water content of the obtained dry konjac pieces is 6.32%, L is 83.98, and the dry konjac pieces are uniform in color and free of color difference.
Example 4:
a preparation method of sulfur-free and browning-free konjak dry slices comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 7KW, the heating time is 45s, and the heating temperature is 70.9 ℃;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 4.8 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 5 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, fumigating the konjac slices with ozone for 25min under the condition that the ozone concentration value is 450-550 PPM, wherein the spreading density of the konjac slices is 0.4g/cm2；
(6) Ultraviolet irradiation: irradiating the konjac slices treated in the step (5) for 25min under ultraviolet light, wherein the paving density of the konjac slices is 0.4g/cm2Ultraviolet light intensity of 0.5mW/cm2；
(7) Microwave drying: the konjac slices treated in the step (6) are subjected to microwave drying treatment in two sections, the temperature of the microwave drying is 65 ℃, and the paving density of the konjac slices is 0.4g/cm2Firstly, continuously heating for 1min under the conditions that the microwave power is 1.0kW and the microwave frequency is 2450MHz to quickly heat the konjac pieces to the drying temperature, then continuously heating for 60min under the conditions that the microwave power is 0.3kW and the microwave frequency is 2450MHz to reduce the final wet-based water content of the konjac dry pieces to below 8 percent to obtain the sulfur-free low-browning konjac dry pieces, and then filling nitrogen to package and store the sulfur-free low-browning konjac dry pieces.
The final wet water content of the obtained dry konjac slice is 7.57%, L is 83.38, and the color of the dry konjac slice is uniform and has no color difference.
Example 5:
a preparation method of sulfur-free and browning-free konjak dry slices comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 8KW, the heating time is 40s, and the heating temperature is 72.4 ℃;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 4.5 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 3 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, fumigating with ozone for 20min under the condition that the ozone concentration value is 450-550 PPM, wherein the spreading density of the konjac slices is 0.6g/cm2；
(6) Ultraviolet irradiation: irradiating the konjac slices treated in the step (5) for 20min under ultraviolet light, wherein the paving density of the konjac slices is 0.55g/cm2Ultraviolet light intensity of 1.2mW/cm2；
(7) Microwave drying: microwave drying the konjac slices treated in the step (6) at the temperature of 75 ℃, wherein the paving density of the konjac slices is 0.6g/cm2Microwave frequency is 2450MHz, microwave power is 0.2kW, and microwave drying time is 80min, so that the final wet-based water content of the konjac pieces is reduced to below 8%, and sulfur-free low-browning konjac dry pieces are obtained and stored after nitrogen-filled packaging.
The final wet basis water content of the obtained dry konjac pieces is 7.92%, L is 82.63, and the dry konjac pieces are uniform in color and free of color difference.
Example 6:
a preparation method of sulfur-free and browning-free konjak dry slices comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 9KW, the heating time is 35s, and the heating temperature is 66.9 ℃;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 5.5 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 4 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, fumigating the konjac slices with ozone for 30min under the condition that the ozone concentration value is 450-550 PPM, wherein the spreading density of the konjac slices is 0.6g/cm2；
(6) Ultraviolet irradiation: irradiating the konjac slices treated in the step (5) for 30min under ultraviolet light, wherein the paving density of the konjac slices is 0.6g/cm2Ultraviolet light intensity of 0.8mW/cm2；
(7) Microwave drying: microwave drying the konjac slices treated in the step (6) at the temperature of 66 ℃, wherein the paving density of the konjac slices is 0.6g/cm2Microwave frequency is 2450MHz, microwave power is 1.5kW, and microwave drying time is 60min, so that the final wet-based water content of the konjac pieces is reduced to below 8%, and sulfur-free low-browning konjac dry pieces are obtained and stored after nitrogen-filled packaging.
The final wet basis water content of the obtained dry konjac slice is 6.62%, L is 82.12, and the dry konjac slice has uniform color and no color difference.
Comparative example 1:
the only difference from the method described in example 1 is that ozone fumigation and ultraviolet irradiation steps are omitted, and the obtained dry konjac slice has a brownish black surface, dark color and poor quality, and has a final wet basis moisture content of 6.34% and L of 74.22.
Comparative example 2:
the method is different from the method of the embodiment 1 only in that the ozone fumigation in the step (5) is to place the treated konjac slices into an ozone sterilizer, and carry out ozone fumigation for 30min under the condition that the ozone concentration value is 250-350 PPM, so that the obtained konjac dry slices are darker in color and poor in quality, the final wet base water content is 6.13%, and L is 74.31. Because the ozone concentration is too low, the enzyme can not be effectively killed, so that the color of the dry konjac slices becomes dark due to browning, the ozone concentration is reasonably increased, the ozone fumigation is carried out under the conditions of limited fumigation time and paving density, the enzyme can be rapidly and effectively killed, and the nutritional ingredients of the konjac can not be reacted and deteriorated due to long-time ozone fumigation, so that the loss of the nutritional ingredients is increased.
Comparative example 3:
the method is different from the method in the embodiment 1 only in that the microwave drying in the step (7) is to apply microwave drying to the treated konjac slices, the microwave frequency is 2450MHz, the microwave power is 0.3kW, the continuous heating time is 90min, the obtained konjac dry slices are darker in color, the konjac slices are not uniformly dried, individual carbonization points are generated, the konjac dry slices have scorched flavor, the loss of nutritional ingredients is large, the moisture content of the final wet base is 7.26%, and L is 70.91.
Experimental example 1:
dried konjac pieces were prepared as described in example 1, and in the slicing in step (4), konjac pieces were cut into pieces having a thickness of 1mm, 1.5mm, 2mm, 4mm, 5mm, 6mm, 7mm, 8mm, respectively, and then subjected to ozone fumigation, ultraviolet irradiation, microwave drying, etc. in the same manner, and the color of the resulting dried konjac pieces was observed and the water content of the dried konjac pieces was measured at the same time, as shown in table 1.
TABLE 1 color and water content of dried konjac slice
Figure DEST_PATH_IMAGE001
As can be seen from the data in the above table, when the thickness of the konjac pieces is less than 1.5mm, the obtained dry konjac pieces have less water content, but uneven color and carbonized black spots, because the thickness of the konjac pieces is too small and the drying rate is too high, the konjac pieces are locally overheated to form scorch, and the nutrition loss is increased; when the thickness of the konjac pieces is larger than 6mm, the water content of the konjac dry pieces is obviously increased, and because the drying rate is low, the drying degree of each part is not uniform, so that the local overheating inside becomes black, and the local color on the surface becomes dark.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (6)

1. A preparation method of sulfur-free and browning-free konjak dry slices is characterized by comprising the following steps: the method comprises the following steps:
(1) cleaning: removing soil from fresh rhizoma Amorphophalli, and washing;
(2) microwave pretreatment: heating the konjak processed in the step (1) in a microwave drying box, wherein the microwave frequency is 915MHz, the microwave power is 7-10 KW, and the heating time is 27-52 s;
(3) pretreatment: peeling the konjac processed in the step (2) and cutting off surface layer pulp, wherein the thickness of the surface layer pulp is 4.5-5.5 mm;
(4) slicing: slicing the konjac processed in the step (3) to obtain konjac slices, wherein the thickness of the konjac slices is 2-5 mm;
(5) ozone fumigation: putting the konjac slices obtained in the step (4) into an ozone sterilizer, and fumigating with ozone for 20-30 min under the condition that the concentration value of ozone is 450-550 PPM;
(6) ultraviolet irradiation: placing the konjac slices treated in the step (5) under ultraviolet light for irradiating for 20-30 min, wherein the ultraviolet light intensity is 0.5-1.5 mW/cm2；
(7) Microwave drying: and (4) microwave drying the konjac pieces processed in the step (6), wherein the microwave frequency is 2450MHz, the microwave power is 0.2-1.5 kW, and the microwave drying time is 60-80 min, so that the final wet basis water content of the konjac pieces is reduced to below 8%, and sulfur-free low-browning konjac dry pieces are obtained and stored after nitrogen-filled packaging.
2. The method for preparing a sulfur-free browning-free konjac dried chip as claimed in claim 1, wherein: the heating temperature in the step (1) is 63.7-74.8 ℃.
3. The konjac without sulfur and browning as claimed in claim 1The preparation method of the dry tablet is characterized by comprising the following steps: in the ozone fumigation step, the spreading density of the konjac pieces is 0.4-0.6 g/cm2。
4. The method for preparing a sulfur-free browning-free konjac dried chip as claimed in claim 1, wherein: in the step of ultraviolet irradiation, the paving density of the konjac pieces is 0.4-0.6 g/cm2。
5. The method for preparing a sulfur-free browning-free konjac dried chip as claimed in claim 1, wherein: in the microwave drying step, the spreading density of the konjac pieces is 0.4-0.6 g/cm2
The method for preparing a sulfur-free browning-free konjac dried chip as claimed in claim 1, wherein: in the step (7), the konjac pieces are subjected to microwave drying treatment in two sections, firstly, the konjac pieces are continuously heated for 1-3 min under the conditions that the microwave power is 1.0kW and the microwave frequency is 2450MHz, so that the konjac pieces are quickly heated to the drying temperature, and then the konjac pieces are continuously heated for 60-80 min under the conditions that the microwave power is 0.3kW and the microwave frequency is 2450MHz, so that the final moisture content of the wet base of the konjac dry pieces is reduced to below 8%.
6. The method for preparing a sulfur-free browning-free konjac dried chip as claimed in claim 1, wherein: the temperature of microwave drying in the step (7) is 65-75 ℃.
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