TWI617245B - Method for extending the shelf life of chilled fresh milk - Google Patents

Abstract

The invention discloses a method for extending the shelf life of a chilled dairy product, which comprises the steps of: separating raw milk of raw milk and obtaining a defatted raw milk; filtering the defatted raw milk through a filter to obtain a membrane-filtered defatted raw milk; The fresh emulsifiable oil is sterilized by an ultra-high temperature instant sterilization method to obtain a sterilized fresh emulsifiable concentrate; the defatted raw milk filtered by the membrane is mixed with the sterilized fresh emulsifiable oil to obtain a raw milk semi-finished product; and the fresh milk semi-finished product is passed through the aforementioned super The high-temperature instant sterilization method is sterilized to obtain a fresh milk product; the fresh milk product is lowered in temperature and aseptically filled to obtain a fresh milk. The aforementioned refrigerated fresh milk produced by the present invention can reduce the change in flavor caused by ultra-high temperature sterilization and can be stored in cold storage for at least six months.

Description

Method for extending the shelf life of chilled fresh milk

The present invention relates to a method for extending the shelf life of a sterilized ultra-high temperature instant sterilized dairy product, and more particularly to a method for retaining the fresh flavor of the aforementioned fresh milk.

Generally, the sterilization method of fresh milk is based on low-temperature long-time pasteurization (LTLT pasteurization) and high-temperature short-time pasteurization (HTST pasteurization). And ultrahigh temperature pasteurization (UHT-pasteurization); while the long-term milk is UHT-sterilization. Different sterilization methods will affect the shelf life and original flavor of the aforementioned fresh dairy products.

The low-temperature long-time pasteurization sterilization method is performed at a temperature of 62 ° C to 65 ° C for 30 minutes; the high temperature short-time pasteurization sterilization method is performed at a temperature of 72 ° C for 15 seconds, and the aforementioned low-temperature long-time sterilization method and high temperature The short-time sterilization method allows the aforementioned fresh milk to retain the original flavor, and the aforementioned fresh milk has a shelf life of 10 days to 14 days at low temperature storage. The ultra-high temperature instant sterilization method utilizes a temperature of 120 ° C to 134 ° C for sterilization for 1 second to 4 seconds. The above-mentioned ultra-high temperature instant sterilization method may cause the original flavor of the fresh milk to be moderately damaged. If the package is filled in a nearly aseptic package, the storage period of the fresh milk in the low temperature storage may be extended to 30 days to 60 days, generally domestically produced in China. The fresh milk is sterilized by the above-described ultra-high temperature instant sterilization method. The ultra-high temperature sterilization method utilizes a temperature of 135 ° C to 145 ° C for sterilization for 2 seconds to 10 seconds. The above-mentioned ultra-high temperature sterilization method may seriously damage the original flavor of the fresh milk, but with aseptic filling, the fresh milk may be stored at room temperature. Under the condition, there is a shelf life of at least six months, and the commercially available long-lasting milk is sterilized by the above-mentioned ultra-high temperature sterilization method, and packaged at normal temperature.

The change in the original flavor of the aforementioned fresh milk is mainly derived from the Maillard reaction produced by the aforementioned fresh milk in the heat sterilization process. The initial stage of the Mena reaction is a chemical reaction between the nucleophilic amino group of the amino acid of the fresh milk and the carbonyl group of the lactose, and the nucleophilic amine group and the nucleophilic group The aforementioned carbonyl group is subjected to an amine carbonyl condensation reaction to form a Schiff base, followed by an Amadori rearrangement. The intermediate phase of the aforementioned Mena reaction causes a Strecker degradation of the protein, at which time the amino acid cleaves and produces carbon dioxide and aldehydes. In the final stage of the aforementioned Mena reaction, a condensation reaction of an aldehyde with an alcohol is carried out, and a melanin substance is produced, and many intermediate products produced in the reaction will affect the color and flavor of the milk.

Therefore, in order to balance the original flavor of the fresh milk and to extend the shelf life thereof, the prior art still has many places for improvement in the sterilization method of the aforementioned fresh milk.

In view of the absence of the prior art, the object of the present invention is to overcome the aforementioned fresh milk by using a defatted raw milk through a membrane filtration technique in combination with mild sterilizing conditions and then performing aseptic filling and packaging at a low temperature. The retention of the original flavor and the extension of its shelf life cannot be balanced.

In order to achieve the above object, the present invention provides a method for extending the shelf life of chilled fresh milk, the steps comprising: (a) separating fresh emulsifiable milk from raw milk to obtain the aforementioned defatted raw milk; (b) the aforementioned steps ( a) the defatted raw milk is filtered through a membrane filter to remove microorganisms, and a membrane-filtered defatted raw milk is obtained; (c) the fresh emulsifiable concentrate of the above step (a) is subjected to ultra-high temperature instant sterilization Sterilizing, obtaining a sterilized fresh emulsifiable oil, and then lowering the sterilizing fresh emulsifiable concentrate; (d) mixing the defatted raw milk after filtering the membrane of the above step (b) with the sterilized fresh emulsifiable concentrate to obtain a raw milk semi-finished product; (e) The raw milk semi-finished product is sterilized by the above-mentioned ultra-high temperature instant sterilization method to obtain a fresh milk product; (f) the fresh milk product is lowered in temperature and aseptically filled to obtain a chilled fresh milk.

According to the present invention, the filter of the above step (b) is a filter having a pore size of 0.8 μm.

According to the present invention, the ultra-high temperature instant sterilization method of the foregoing step (c) selects a method for rapidly heating and rapidly reducing the temperature, including, but not limited to, a plate heating method and a tube heating method, and using a temperature of 120 ° C to 134 ° C. Sterilize for 2 seconds to 10 seconds. In a preferred embodiment, the ultra-high temperature instant sterilization method of the aforementioned step (c) is a plate heating method.

According to the present invention, the lowering temperature of the aforementioned step (c) is lowered to between 50 ° C and 60 ° C.

According to the present invention, the ultra-high temperature instantaneous sterilization method of the above step (e) is sterilized by using a temperature of 120 ° C to 134 ° C for 3 seconds to 10 seconds.

Preferably, the fresh milk product of the aforementioned step (f) is lowered to a temperature below 10 °C.

More preferably, the fresh milk product of the aforementioned step (f) is lowered to a temperature below 8 °C.

Preferably, the fresh milk product of the aforementioned step (f) is aseptically filled into a sterile packaging material.

More preferably, the aforementioned sterile packaging material is a Tetra Pak which is composed of a double-layer polyethylene (polyethylene), an aluminum foil and polyethylene from the outside to the inside.

The most innovative key point of the above-mentioned refrigerated fresh milk prepared by the invention is that the microorganisms are removed through the above-mentioned filter membrane filtration technology, and combined with the mild sterilization conditions of the ultra-high temperature sterilization method, thereby reducing the plum produced by the high temperature. The reaction is carried out to retain the original flavor of the aforementioned raw milk. Finally, the fresh milk is aseptically packaged at a low temperature to extend the shelf life of the fresh milk, and the chilled fresh milk can be stored for at least 6 months at a temperature of 4 ° C to 8 ° C. The present invention provides an effective improvement in maintaining both the retention of the original flavor of the chilled fresh milk and the extension of its shelf life.

Figure 1 is a flow chart of the present invention.

The following examples are intended to illustrate the invention. The examples are not intended to limit the scope of the invention in any way, but are used to illustrate the materials and methods of the invention.

The fresh cream is separated from the raw milk to obtain a skim milk. The fresh milk is sterilized by ultra-high temperature by a plate heating method, and heated at 120 ° C - 134 ° C for 2 seconds to 10 seconds to obtain a sterilized fresh emulsifiable concentrate, and then the temperature of the sterilized fresh emulsifiable concentrate is lowered to 50 ° C. Up to 60 ° C. The aforementioned defatted raw milk was filtered through a filter having a pore size of 0.8 μm, and a membrane-filtered defatted raw milk was obtained.

The sterilized fresh emulsifiable concentrate is mixed with the defatted raw milk filtered by the membrane to form a raw milk semi-finished product, and is rapidly sterilized by ultra-high temperature, and heated at 120 ° C - 134 ° C for 3 seconds to 10 seconds to obtain a fresh milk product. The temperature of the fresh milk product is lowered to below 10 ° C, and aseptically filled into a sterile package to obtain a fresh milk. The aforementioned aseptic packaging material is a Tetra Pak material which is composed of a double-layer polyethylene, an aluminum foil and polyethylene from the outside to the inside.

The chilled fresh milk was stored at 8 ° C and 12 ° C, and the total amount of microorganisms of the aforementioned chilled fresh milk was separately detected for 0 months to 6 months. The detection of the aforementioned microorganisms includes the total number of bacteria formed per ml (Colony forming units/ml, CFU/ml), mold/yeast count (CFU/ml), Escherichia coli (CFU/ml), and Escherichia coli ( CFU/ml), heat-resistant spores at 80 °C (CFU/ml) and heat-resistant spores at 100 °C (CFU/ml).

The above method for detecting the total number of bacteria is the aforementioned fresh milk After serial dilution, 0.1 ml was dispensed into a plate count agar (PCA) by aseptic operation, and the above-mentioned serially diluted fresh milk was quickly spread and spread at 35 ° C using a sterile curved glass rod. The culture was carried out for 48 ± 2 hours under the environment. In the above dilution method, 10 ml of the above-mentioned chilled fresh milk diluted 10 times is added to 90 ml of the dilution liquid, and a series of dilution detection liquids such as 100 times, 1000 times, and 10000 times are sequentially prepared. The aforementioned dilution is a 0.1% peptone diluents; the aforementioned plate count medium contains 0.5% tryptone, 0.25% yeast extract, 0.1% glucose, and 1.5% amaranth. After the chilled fresh milk is cultured, two of the aforementioned plate counting mediums of 25 to 250 colonies are selected for counting, and the average number of colonies of the two plate counting mediums is multiplied by the dilution factor, and the total number of microorganisms is obtained.

The method for detecting the number of molds/yeasts is to serially dilute the chilled fresh milk, and 0.1 ml of the solution into the Dichloran rose bengal chloramphenicol agar (DRBC) is aseptically operated. The above-mentioned serially diluted chilled fresh milk was quickly spread and spread using a sterile curved glass rod, and cultured in a dark environment at 25 ° C for 5 days. In the above dilution method, 10 ml of the above-mentioned chilled fresh milk diluted 10 times is added to 90 ml of the dilution liquid, and a series of dilution detection liquids such as 100 times, 1000 times, and 10000 times are sequentially prepared. The aforementioned dilution is a 0.1% peptone dilution; the dichloropyranine chloramphenicol medium comprises 0.5% peptone, 1% glucose, 0.1% potassium dihydrogen phosphate (KH ₂ PO ₄ ), 0.05% magnesium sulfate ( MgSO ₄ ‧7H ₂ O), 0.25% rose bengal, 0.02% dichloran, 1.5% amaranth, and 0.01% chloramphenicol. After the chilled fresh milk is cultured, two of the aforementioned plate counting mediums of 25 to 250 colonies are selected for counting, and the average number of colonies of the two plate counting mediums is multiplied by the dilution factor, and the total number of microorganisms is obtained.

The above-mentioned Escherichia coli group and the above-mentioned Escherichia coli detection method are obtained by serially diluting the above-mentioned chilled fresh milk, and 0.1 ml of the sterilized fresh milk is injected into a Kromagar medium (CHROMagar ECC), and the sterile curved glass rod is quickly used. The above-mentioned serially diluted fresh milk was evenly spread and incubated at 37±1 ° C for 24 hours. In the above dilution method, 10 ml of the above-mentioned chilled fresh milk diluted 10 times is added to 90 ml of the dilution liquid, and a series of dilution detection liquids such as 100 times, 1000 times, and 10000 times are sequentially prepared. The aforementioned dilution is a 0.1% peptone dilution; the aforementioned coma medium contains 3.28% DHROMagar. After the chilled fresh milk is cultured, two of the aforementioned plate counting mediums of 25 to 250 colonies are selected for counting, and the average number of colonies of the two plate counting mediums is multiplied by the dilution factor, and the total number of microorganisms is obtained. The species of the microorganism is determined by observing the color of the colony after the culture, and if the colony is blue, it is Escherichia; if the colony is red, it is other (fecal) bacteria of the E. coli; if the colony is present Colorless, it is another Gram-negative bacteria.

The method for detecting the heat-resistant spores of 80 ° C is to dilute the chilled fresh milk by 10 times with a 0.1% peptone dilution, and to dispense 10 ml, 1 ml, and 0.1 ml into 100 ml of the plate counting medium by aseptic operation. The aforementioned plate counting medium contains 0.5% tryptone, 0.25% yeast extract, 0.1% glucose and 1.5% amaranth, at 80 The °C water bath was heated for 30 minutes and then quickly placed in a cooling water. The above-mentioned plate counting medium containing chilled fresh milk was divided into five portions, and each was poured into five plate-shaped plate samples, and cultured at 35 ° C for 48 hours, and the number of colonies was counted.

The method for detecting the heat-resistant spores of 100 ° C is to dilute the chilled fresh milk by 10 times with 0.1% peptone dilution, and to dispense 10 ml, 1 ml and 0.1 ml into 100 ml of DTA medium (Destrose) by aseptic operation. Tryptone agar), heated in a 100 ° C water bath for 5 minutes, then quickly placed in a cooling water. The above-mentioned DTA medium containing chilled fresh milk was divided into five portions, and each was poured into five plate culture samples, and cultured at 55 ° C for 48 hours, and the number of colonies was counted.

The results of microbial analysis of the aforementioned chilled fresh milk are shown in Table 1.

Generally, the sterilization method and shelf life of the aforementioned fresh milk are as shown in Table 2 (Tamime, A.Y. (Ed.). 2009. Milk processing and quality management. p. 196. John Wiley & Sons).

As a result of comparing Table 1 and Table 2, it was found that the aforementioned chilled fresh milk was stored at 8 ° C and 12 ° C for 0 months to 6 months, and no microorganisms were detected. This result shows that the shelf life of the aforementioned chilled fresh milk can be effectively extended by the method of the present invention.

In summary, the fresh milk produced by the invention is firstly removed by the filter membrane filtration method, and then sterilized by mild sterilization conditions, thereby reducing the Mena reaction of the fresh milk due to high temperature. And retain the original flavor of the aforementioned fresh milk. Finally, the aforementioned fresh milk is at a low temperature. Sterile filling and packaging in the environment to extend the shelf life of the aforementioned fresh milk. According to the chilled fresh milk manufactured by the present invention, the change of the original flavor of the chilled fresh milk caused by the ultra-high temperature instant sterilization can be avoided, and the chilled fresh milk can have at least 6 in an environment of 4 ° C to 8 ° C. The shelf life of the month.

Claims (7)

A method for extending the shelf life of chilled fresh milk, the method comprising the steps of: (a) separating the fresh emulsifiable milk from the raw milk to obtain a defatted raw milk; and (b) passing the defatted raw milk of the aforementioned step (a) through a filter Filtration is performed to obtain a membrane-filtered degreased raw milk, wherein the filter membrane is a filter membrane having a pore size of 0.8 μm; (c) the fresh cream of the above step (a) is sterilized by an ultra-high temperature instant sterilization method to obtain a The sterilized fresh emulsifiable oil is further reduced in temperature by the sterilizing fresh emulsifiable oil, and the ultra-high temperature instant sterilizing method is sterilized by using a temperature greater than 120 ° C to 134 ° C; (d) the defatted raw milk after filtering the membrane of the above step (b) and the sterilizing After the fresh emulsifiable concentrate is mixed, a raw milk semi-finished product is obtained; (e) the raw milk semi-finished product is sterilized by the ultra-high temperature instant sterilization method to obtain a fresh milk product, and the ultra-high temperature instant sterilization method is performed at a temperature of 120 ° C to 134 ° C. Sterilize for 3 seconds to 10 seconds; (f) lower the temperature of the aforementioned fresh milk product and perform aseptic filling to obtain a fresh milk. The method for extending the shelf life of the chilled fresh milk as described in claim 1, wherein in the step (c), the ultra-high temperature instant sterilization method performs sterilization for 2 seconds to 10 seconds. The method for extending the shelf life of the chilled fresh milk according to claim 1, wherein in step (c), the temperature of the sterilized fresh emulsifiable concentrate is lowered to between 50 ° C and 60 ° C. The method for extending the shelf life of the chilled fresh milk as described in claim 1, wherein in step (f), the reduced temperature of the fresh milk product is reduced to below 10 °C. The method for extending the shelf life of the chilled fresh milk as described in claim 1, wherein in step (f), the reduced temperature of the fresh milk product is lowered to below 8 °C. The method of claim 1, wherein the fresh milk product is aseptically filled into a sterile packaging material in the step (f). The method for extending the shelf life of the refrigerated fresh milk according to claim 6, wherein the aseptic package material is a Tetra Pak material, which is made of polyethylene (polyethylene), polyethylene, aluminum foil (aluminum). Foil) and polyethylene.