Steam pasteurization method for freeze-dried food

Abstract

The invention discloses a steam pasteurization method for freeze-dried food. The steam pasteurization method comprises the following steps: 1) determining sterilization temperature corresponding to the type of freeze-dried food to be sterilized, and determining target water activity at the sterilization temperature; 2) cooling the food in the step 1) to cooling temperature corresponding to the type of the food; 3) exhausting air in a sterilization chamber where the food is located; 4) introducing water vapor into the sterilization chamber, regulating vapor flow after the temperature of the food is up to the sterilization temperature, maintaining the temperature of the food to be the sterilization temperature for a specific sterilization time period, and then stopping introduction of watervapor; 5) lowering pressure in the sterilization chamber by vapor trapping; and 6) after the pressure in the sterilization chamber reaches or is close to water saturation pressure, corresponding to the cooling temperature before sterilization, introducing clean air into the sterilization chamber until a vacuum state is relieved, and taking out the food.

Description

technical field

[0001] The invention relates to a method for steam sterilization of food, in particular to a method for steam pasteurization of freeze-dried food. Background technique

[0002] Microbial contamination of low-moisture foods has become a new food safety issue in recent years, and related food-borne illnesses and food recalls have occurred many times, involving foods such as dried fruits, spices, and pet dry food. The most frequently occurring pathogens were Salmonella, followed by Listeria monocytogenes and Escherichia coli O157:H7, all of which exhibited increased thermotolerance at low water activity.

[0003] Water activity refers to the ratio of the saturated vapor pressure of food to the saturated vapor pressure of pure water at the same temperature, and is an expression of the free water content in food. Foods with low water activity generally refer to foods with water activity less than 0.7. Foodborne pathogenic bacteria such as Salmonella cannot grow a...

Examples

Embodiment 1

[0063] The sterilization method of the present invention will be further explained below by taking a sterilization process of freeze-dried chicken with a water content of 2.8% as an example.

[0064] (1) Parameter setting and calculation

[0065] The pasteurization temperature to be employed was set at 75°C with a target water activity of 0.75. Check the isotherm hygroscopic line of this material, when the temperature is 25 ℃ and the water content is 2.8%, the water activity is 0.06, when the temperature is 75 ℃ and the water activity is 0.75, the corresponding moisture content is 8.4%. The constant pressure specific heat capacity of the freeze-dried chicken is 1.7kJ / (kg°C), and the temperature of the material before steam sterilization is 3°C calculated by the aforementioned formula (2).

[0066] (2) vacuuming

[0067] In the freeze-dried chicken, several pieces were inoculated with Enterococcus faecalis (ATCC 8459), and the inoculation quantity was 6.3×10 8 CFU / g; Cool th...

technical field

[0001] The invention relates to a method for steam sterilization of food, in particular to a method for steam pasteurization of freeze-dried food. Background technique

[0002] Microbial contamination of low-moisture foods has become a new food safety issue in recent years, and related food-borne illnesses and food recalls have occurred many times, involving foods such as dried fruits, spices, and pet dry food. The most frequently occurring pathogens were Salmonella, followed by Listeria monocytogenes and Escherichia coli O157:H7, all of which exhibited increased thermotolerance at low water activity.

[0003] Water activity refers to the ratio of the saturated vapor pressure of food to the saturated vapor pressure of pure water at the same temperature, and is an expression of the free water content in food. Foods with low water activity generally refer to foods with water activity less than 0.7. Foodborne pathogenic bacteria such as Salmonella cannot grow a...

Examples

Embodiment 1

[0063] The sterilization method of the present invention will be further explained below by taking a sterilization process of freeze-dried chicken with a water content of 2.8% as an example.

[0064] (1) Parameter setting and calculation

[0065] The pasteurization temperature to be employed was set at 75°C with a target water activity of 0.75. Check the isotherm hygroscopic line of this material, when the temperature is 25 ℃ and the water content is 2.8%, the water activity is 0.06, when the temperature is 75 ℃ and the water activity is 0.75, the corresponding moisture content is 8.4%. The constant pressure specific heat capacity of the freeze-dried chicken is 1.7kJ / (kg°C), and the temperature of the material before steam sterilization is 3°C calculated by the aforementioned formula (2).

[0066] (2) vacuuming

[0067] In the freeze-dried chicken, several pieces were inoculated with Enterococcus faecalis (ATCC 8459), and the inoculation quantity was 6.3×10 8 CFU / g; Cool th...