Insufficient sterilization of pet cans can lead to swelling and excessive toxins caused by Clostridium botulinum and heat-resistant spore forming bacteria, endangering the health of pets; Excessive sterilization leads to denaturation of meat protein, loss of B vitamins, drying of canned food, pets not liking it, and a sharp decline in product repurchase rate. In fact, the sterilization logic of pet canned food has already formed a mature system in the canning technology of the food industry, and the insulation process after sterilization is the "last line of defense" to safeguard the safety bottom line and lock in the nutritional palatability. If the insulation is not proper, it is easy to cause secondary pollution, uneven cooling of the can, and damage to the can body, which may also affect the stability of the bacterial community inside the can, rendering the previous efforts of precise sterilization useless. This article combines food grade standards and practical techniques for precise sterilization and post sterilization insulation of pet canned food.

Different acid levels of pet canned food have different sterilization requirements

In the food industry, the primary criterion for sterilization of canned food is acidity (pH value), which is fully applicable to pet canned food. According to classification, the sterilization requirements for cans of different acid grades are completely different, which directly determines the subsequent sterilization intensity and process selection.

1. Low acidity pet canned food (pH>5.0)

The mainstream canned foods in the market include pure chicken cans, beef cans, fish and shrimp cans, as well as mixed cans with a meat content of over 70% (such as chicken pumpkin cans, beef vegetable cans). The risk bacteria of this type of canned food are consistent with low acid canned food in humans, such as Clostridium botulinum (widely distributed in nature, with a high probability of raw material contamination, can grow and produce toxins in environments with pH>4.6, and pets have much lower tolerance to its toxins than humans)

P.A.3679 Bacillus subtilis, which is more heat-resistant than Clostridium botulinum and does not produce toxins but can cause canned food to spoil, must be sterilized under pressure at 105-121 ℃ to completely eliminate the risk bacteria.

2 Acidic pet cans (pH 3.7~4.6)

Most of them are high fruit and vegetable additive formulas (such as blueberry chicken cans, apple duck meat cans, with a fruit and vegetable ratio of over 50%), corresponding to non spore acid resistant bacteria and acid resistant spore resistant bacteria. The reference standard only requires boiling water or atmospheric pressure sterilization below 100 ℃, which can ensure safety and reduce the damage of vitamin C and dietary fiber in fruits and vegetables.

If you want to reduce the sterilization intensity of low acid pet canned food (reduce nutrient loss), you can refer to the idea of low acid adding acid to acid conversion: without affecting the palatability of pets, add a small amount of natural organic acids (such as citric acid, malic acid) to make the final equilibrium pH of the canned food<4.6. At this time, the sterilization temperature can be reduced from 121 ℃ to 100 ℃, which can also make the meat muscle fibers more tender and improve palatability.

The core indicator for measuring sterilization accuracy - F value

Many practitioners are puzzled: "Why are some canned foods safe and fresh, while others are rotten or dry?" The answer is hidden in the F-value, which is the core indicator for measuring sterilization accuracy. The calculation formula and judgment criteria are clear, directly determining the sterilization effect and nutrient retention.

2.1 Safety F-value (F safety) The calculation of safety F-value (F safety) needs to be determined based on the bacterial load and allowable spoilage rate of the raw materials.

The formula is F A=D121 ℃ (Iga Igb). Among them, D121 ℃ refers to the time required to kill 90% of the target bacteria at 121 ℃ (such as Bacillus subtilis D121 ℃ -4.0 min, which is a common heat-resistant bacterium in low acid tanks); A is the total bacterial load of a single can (such as 400g chicken can, if the bacterial load of raw materials is less than 2/g, then a-400x2-800/can); B is the allowable corruption rate (pet food has stricter requirements, it is recommended to be less than 3x10-4, which is within 0.03%).

Taking a 400g chicken can as an example, F A=4.0x (Ig800-Ig3x10-4) -24.5min is the safety bottom line for sterilization.

2.2 Actual F value (F actual) The calculation of actual F value (F actual) requires monitoring the center temperature of the tank during the sterilization process, calculated according to F-At2Lm n (Δ t is Lm=0.2512 during temperature monitoring)

Interval, Lm is the mortality rate at the corresponding temperature, for example, Lm=1.012 at 121 ℃, Lm=0.7943 at 20 ℃, and if the actual sterilization protocol is "10 '-25' -10 '/121.1 ℃" (heating for 10 minutes, constant temperature for 25 minutes, cooling for 10 minutes) at 115 ℃, after calculation, F is approximately 25.2 minutes. When F is greater than F, the sterilization is both up to standard and not excessive; If F is less than F, it indicates insufficient sterilization and a risk of spoilage; If F is much higher than F (such as more than 30 minutes), meat muscle fibers will contract excessively, and palatability will decrease by more than 30%.

Sterilization method for pet canned food

Normal pressure sterilization, pressure sterilization, and new gas conditioning sterilization in the food industry need to be tailored to the packaging and formula characteristics of pet cans, combined with F-value control, to achieve a balance between safety and nutrition:

3.1 Atmospheric sterilization (<100 ℃)

Suitable for acidic pet cans in glass bottles and soft packaging.

When operating, three points should be noted: ① Preheat the canned food to 70 ℃ before entering the pot, to avoid sudden drops in water temperature and prolong the heating time; ② When the glass jar is filled with water, the temperature difference should not exceed 60 ℃ to prevent breakage; ③ During the sterilization process, the canned food should be submerged 10-15cm below the water surface to ensure uniform temperature and avoid insufficient local sterilization.

3.2 Static pressure sterilization (105~121 ℃)

It is a standard configuration for low acid pet cans packaged in tinplate and aluminum foil.

The key step is to exhaust, and sufficient exhaust time and steam supply are necessary conditions for eliminating the air inside the pot. The sign of completely exhausting the air is that the exhaust valve outlet gas is gray white, and the sterilization pot gauge pressure is consistent with the thermometer reading. Otherwise, residual air in the pot will cause false heating (displayed as 121 ℃, actual local temperature is only 110 ℃), leaving a safety hazard; During the cooling stage, compressed air should be used to control the back pressure and prevent deformation of the can (especially for soft packaging cans, insufficient back pressure can easily break the bag).

3.3 New gas containing conditioning and sterilization

Suitable for high-end fresh food grade pet cans.

Adopting a gentle method of wave shaped hot water spray, multi-stage heating, and two-stage rapid cooling, with the first stage preheating, the second stage conditioning for flavor, and the third stage sterilization (using a bimodal system method), the characteristic is that the internal temperature of the food rises quickly, and the heating temperature and time are limited to a low limit. The sterilization temperature is 120-123 ℃ and the time is only 4-6 minutes, which is 60% shorter than traditional pressure sterilization. It can preserve the freshness of meat to the maximum extent (reducing the loss of flavor substances by 50%), and the retention rate of B vitamins is increased to over 85%. It is particularly suitable for high-end products that mainly use human grade raw materials and fresh taste.

Thermal insulation plan for pet canned food after sterilization

After sterilization of pet canned food, it does not directly enter the cooling and packaging process, but needs to undergo scientific insulation treatment. The core purpose is to identify and fill gaps, and to investigate cans that are not thoroughly sterilized; Stabilize the environment inside the tank, avoid damage to the tank body and secondary pollution caused by excessive temperature differences, lock in nutritional flavors, and reduce the damage to meat taste and vitamins caused by sudden temperature changes. Based on the food grade canned food insulation standards, the practical plan needs to be developed by category and packaging, with a focus on controlling the insulation temperature, time, and environment.

Core Principles of Thermal Insulation

Following the three principles of slow cooling, constant temperature settling, and sterile environment: the temperature of sterilized cans is relatively high (80-121 ℃), and it is strictly prohibited to directly place them in low-temperature environments (such as cold water or cold storage) to avoid excessive temperature differences between the inside and outside of the cans, which can cause stress and lead to tin cans collapsing, glass cans exploding, and soft packaging bags breaking; During the insulation process, it is necessary to maintain a sterile environment to prevent secondary contamination after the can body is damaged; At the same time, by keeping it at a constant temperature, the small amount of heat-resistant spores remaining in the tank are fully exposed, which facilitates the subsequent inspection of non-conforming products.