How to packaging frozen food?

On June 25, 2021, the FDA and Avanti Frozen Foods Pvt. Ltd simultaneously issued a product recall statement for frozen cooked shrimp with a specific code, because they may be contaminated by Salmonella. So far, there have been 6 reports of Salmonella-related diseases related to the distribution of these cooked shrimps. Based on previous tests conducted on frozen cooked shrimp imported by Avanti Frozen Foods, the FDA found that it contained Salmonella, thus determining the possibility of contamination.

AVANTI FRZON FOODS’s frozen shrimp sanitation incident once again aroused people’s discussion on the safety and sanitation of frozen food. Is frozen food safe? What are the advantages and disadvantages? Below, we will discuss this issue from aspects of frozen food production, storage, and packaging.

Many consumers often confuse quick freezing and freezing, but in fact, the two concepts are completely different. In the process of food freezing, the most critical link in the process of crystallization of water molecules inside and outside the cell. The size and distribution of ice crystals in the food tissue have a great influence on the quality of the food. Food freezing technology is generally divided into three types – slow Freezing, medium-speed freezing, and ultra-low temperature quick freezing.

Slow freezing means it takes a few hours, even more than ten hours, the core temperature of the food can reach the temperature required for the quality of the food, such as minus 18 degrees. The freezing function of household refrigerators belongs to slow freezing. Slow freezing will form larger ice crystals in the tissue space outside the cells, which will destroy the tissue structure of the food and make the food lose its reconstitution capacity. In the end, it is impossible to achieve long-term fresh-keeping, and can only ensure that the food does not deteriorate within a certain period of time.

Medium-speed freezing refers to that within 30 minutes to 3-5 hours, the core temperature of the food reaches the temperature required for the quality of the food, such as minus 18 degrees. Most frozen product manufacturers will use fans to drive the flow of cold air (-15℃to -18℃ to complete the freezing of food within a few hours, that is freezing at a medium speed.

The medium-speed freezing technology cannot pass the “ice crystal formation zone” quickly because the cooling speed is not fast enough. Once thawed, the cell fluid will be lost, the original taste of the food will become weaker, the taste and other physical indicators will decrease, and the nutrition will also be lost. Once thawed, the cell fluid will be lost, the original taste of the food will become weaker, the taste and other physical indicators will decrease, and the nutrition will also be lost.

However, the change of physical properties is smaller when freezing at a medium speed than when freezing at a slow speed. So in fact, medium-speed freezing cannot lock fresh, and it can only ensure that the food does not deteriorate within a certain period of time.

The liquid ammonia refrigeration technology used in some quick-frozen food freezers belongs to ultra-low temperature rapid freezing. In a few minutes to ten minutes, the temperature of the food center can reach -18℃, which is required for locking the freshness of food. In the shortest time, let the temperature quickly pass through the largest crystallization zone(ice crystal formation zone -1℃ to -5℃), the temperature drops rapidly so that the water molecules inside and outside the cell simultaneously generate a large number of crystals (the shorter the time, the smaller the ice crystals are) with a small volume (less than 5 microns in diameter).

In this way, water molecules form evenly distributed fine crystals in the tissue, will not pierce the cell membrane (the diameter of animal cells is generally above 10 microns), ensure the integrity of the food microstructure, there is very little loss of cell fluid after thawing, guarantee its reversibility to the greatest extent, maintain the fresh taste, taste, and nutrition, to achieve the goal of long-term keeping fresh.

Generally speaking, quick-frozen food refers to products that are quickly frozen at a temperature of -30°C or lower. When the core temperature of the food reaches -18°C, the freezing process is declared to be over. Ordinary frozen foods are slow frozen foods, which refer to foods that are frozen at a temperature higher than -30°C (generally -18°C to -23°C), and are generally suitable for the processing of whole white meat and whole poultry foods.

The main difference between quick-frozen food and ordinary freezing is the freezing rate. The freezing time of quick-frozen food is generally less than 30 minutes, while the freezing of ordinary frozen food requires more than 30 minutes or even more than ten hours. The quick-freezing technology greatly increases the production efficiency of freezing equipment, brings great convenience to food processing enterprises.

Both quick-frozen food and ordinary frozen food must be stored in an environment below -18°C to reduce the energy loss of food.

Quick-frozen food refers to all kinds of fresh foods that have undergone appropriate pre-treatment and processing, and are immediately frozen by quick-freezing technology, and can be transported, stored, and sold under freezing conditions, such as quick-frozen steamed buns, quick-frozen dumplings, frozen rice ball, quick-frozen steamed buns, flower rolls, spring rolls, etc.

Frozen food now mainly includes five categories – fruits and vegetables, aquatic products, meat, poultry and eggs, rice and noodle products, and convenience foods. The biggest advantage of quick freezing is to preserve the original quality of food completely at low temperature ( At the same time, part of the free water of the cells is frozen and the water activity is reduced), without the help of any preservatives and additives, the nutrition of the food is preserved to the maximum extent. The food stored in this way has the advantages of delicious, convenient, healthy, hygienic, nutritious, and affordable.

Will the nutrition of quick-frozen food be “frozen”? Related experiments have proved that frozen fruits and vegetables do not lose more nutrients than fresh fruits and vegetables. Frozen fruits and vegetables will soon be frozen at -18°C as soon as they are picked. At this temperature, the respiration of fruits and vegetables is almost stagnant, and microorganisms cannot grow and reproduce. In theory, it is more helpful for the retention of nutrients. Studies have found that the sugar, soluble protein, amino acids, and vitamin C of quick-frozen fruits and vegetables are not much worse than fresh fruits and vegetables.

Meat mainly provides protein and minerals. Under extremely low-temperature conditions, the protein and mineral machinery will not change, so the nutritional value of frozen meat will hardly be lost. However, the problem with frozen meat may be that the taste is slightly worse because if it is frozen for a long time, the meat will gradually lose water and the taste will not be so tender.

The quick-freezing process of food can reduce the activity of water in the food matrix, inhibit the activity of microorganisms and many enzymes, reduce the speed of various chemical and biochemical reactions, and slow down the rate of food decay and deterioration, thereby maximizing the original freshness of natural foods. Degree, color, flavor, and nutritional content are also the characteristics of quick-frozen food.

Therefore, quick-frozen products still have a certain degree of nutrition, and there will be a small amount of nutrient loss during the freezing process. The quality of frozen food largely depends on the quality of raw food and the manufacturing process. If the temperature of the product is not properly maintained throughout the cold chain, the quality will also be affected.

The processing of frozen food includes three stages – pre-treatment, freezing, and frozen storage. Depending on the frozen food, pre-treatment may involve processes such as blanching, heat treatment, immersion treatment, and freeze protection. An effective freezing process can only maintain the existing quality of the food, but cannot improve it. Therefore, these pre-treatment processes are to maintain the quality and safety of frozen food.

For example, vegetables are usually blanched with steam or hot water to slow down the chemical and physical changes that may occur during storage. However, fruits are usually immersed in ascorbic acid or various sugar solutions to minimize browning. Meat products, fish, and some vegetables will undergo heat treatment to kill surface microorganisms and help them maintain their original nutrition and taste as much as possible after thawing.

The original product of quick-frozen food is pre-processed, and the next processing technology is quick-freezing. Freezing methods can also be divided into two categories according to different types of frozen foods-freezing separately before packaging and freezing after packaging. 

IQF (Individual Quick Freezing) refers to each piece of food that is individually frozen before packaging. Common examples include fruits (i.e. blueberries or strawberries), vegetables (i.e. peas, corn, green beans), seafood (i.e. scallops or shrimps), poultry (i.e. a single chicken breast), or even whole poultry products, such as frozen turkey, are also processed under the IQF method. Products that are frozen after packaging refers to bulk frozen foods that have been packaged before freezing.

Although all these freezing methods are used in the frozen food processing industry, the most important thing for improving productivity is that companies need to design a set of comprehensive freezing equipment to adapt to all stages of the freezing process and to optimize the entire freezing system as a whole.

When goods are transferred between the freezer, cold storage, and refrigerated trucks, they must be temporarily stored at the low-temperature unloading terminal. The low-temperature unloading dock is a fully enclosed structure, which effectively controls the temperature in the unloading area. In this way, refrigerated trucks, low-temperature unloading docks, cold storage, and freezer storage form a constant temperature cargo storage space, which allows the cargo to be stored, handled, selected, and transported at a constant temperature, ensuring the integrity of the cold chain, thereby ensuring food safety and quality, and minimize product loss.

Many people think that frozen food tastes good and it is very convenient to eat. However, do you know that eating frozen food is actually harmful?

First, the nutrients in frozen food will gradually be lost.

As we all know, fresh food is high in nutrients, while quick-frozen food will cause the loss of nutrients. In real life, dumplings are a very common quick-frozen food. Because the temperature is too low, the vegetables and meat fillings in them will lose part of their nutrients during processing.

During transportation and storage, the vitamins in the food will gradually be lost. Moreover, as the storage time becomes longer and longer, the loss of these nutrients will become more and more serious. Therefore, compared with homemade fresh food, the nutritional value of frozen food has actually been greatly discounted.

Second, the total number of colonies in quick-frozen food exceeds the standard.

Quick-frozen food can be said to be relatively unhygienic. Many quick-frozen foods contain a lot of bacteria, especially bulk quick-frozen foods. It is possible that because the raw material itself carries bacteria, the bacteria continue to multiply during the processing, the production personnel carries the bacteria, the mechanical equipment is not clean and other reasons, and various pathogenic microorganisms are brought into it before freezing.

Although low temperature can inhibit the reproduction of microorganisms, it cannot effectively kill them. Once the temperature is restored to a suitable temperature, the microorganisms will become active again, thereby increasing hidden dangers to health.

Third, oxidative deterioration of food occurs.

In the storage process of quick-frozen food, with the oxidation of fat, the taste and appearance will change or even deteriorate, which poses a great threat to health.

Once frozen food is contaminated, it may become a vector for virus transmission. Therefore, for production enterprises, it is necessary to ensure the sanitation and safety of food from the source, adopt reasonable processing and packaging techniques to ensure the safety of frozen food.

(1). The raw materials to be processed must be fresh and non-polluted products to build a high-standard purification workshop to ensure the sanitation and safety of the production environment.

(2). The air shower room can be used to solve the hygiene problems of the operators. The air shower room can well prevent the pollution problems caused by the operators entering and leaving the production workshop.

(3). Human beings have a relatively large potential pollution hazard in food processing. Therefore, it is not only necessary to clean the operators entering and leaving the workshop, but also to minimize the participation of labor in the production process, which requires the production enterprise to use highly automatic production equipment.

(4). To ensure that food is not contaminated by microorganisms, sterilization is also very important. Although some frozen foods can reach commercial aseptic standards after being processed, they are still vulnerable to contamination in the subsequent freezing and packaging links. Therefore, it is necessary to sterilize the packaged food again.

(5). Establish a complete refrigeration chain with high standards to maintain suitable low-temperature conditions throughout the entire process of raw materials (picking, catching, purchasing, etc.), production, processing, transportation, storage, and sales and circulation, to ensure food quality and reduce loss.

(6). Use an intelligent, efficient, food packaging machine that meets the relevant requirements and regulations of food processing machinery to complete the packaging. Consumers’ requirements for food and its packaging are constantly improving. Among them, safety occupies the first place. This is not just a question of whether the food is hygienic, but also a part of the “responsibility” of food packaging machinery.

Our automatic frozen food packaging machine is fully in line with the hygiene and safety of food processing machines.

(1). The shell and food contact parts of the filling machine are made of 304 or 316 stainless steel, which is non-toxic, non-absorbent, and corrosion-resistant. Does not affect the odor of the product, wear-resistant. During cleaning and disinfection, the machine can maintain its inherent shape, shape, color, transparency, toughness, and other characteristics.

(2). The appearance of the machine is smooth, without edges and corners, and without spikes.

(3). The connection part of the machine adopts the continuous welding method of argon arc welding, the welding seam is smooth, and there is no pit.

(4). The entire filling station is equipped with a protective cover.

(5). All parameters are adjusted and set on the touch screen. From automatic feeding, metering, filling, sealing to finished product output, it is highly automated, without manual involvement in the entire packaging process.

According to different types of packaging bags, our frozen food packaging machines include the Vertical Form Fill Sealing Machine and Automatic Premade Pouch Fill and Seal Machine, they are different in filling process and packaging performance.

The Similarities:

Both machines can be used to package quick-frozen fruits, quick-frozen vegetables, quick-frozen chicken, quick-frozen dumplings, quick-frozen rice balls, quick-frozen meatballs, quick-frozen corn kernels, quick-frozen edamame, quick-frozen carrots, and other products. The measuring device can be used for measuring cups or multi-head combination electronic scales. The filling accuracy of the measuring cups is lower than the electronic scale.

The operation process is relatively simple, and the degree of intelligence is relatively high. The adjustment or setting of related packaging parameters can be completed on the touch screen, without any manual adjustment.

The model of the machine is distinguished according to the width of the bag. For example, 420 in SK-420 means that the maximum width of the finished bag is 420mm. The material of the bag can be various heat-sealing composite plastic materials. The coding type can be ribbon coding or stainless steel stamping coding. During the filling process, nitrogen can be filled to extend the shelf life.

The Difference:

(1). Applicable bag types.

A vertical form fill sealing machine is suitable for packing raw material is plastic stretch film. When the weight of quick-frozen products is more than 500g, it can only be used for back-sealing. The automatic premade pouch fill and seal machine can pack all kinds of heat-sealing premade pouches, such as three-side sealing pouches, four-side sealing pouches, back sealing pouches, zippered bags, gusseted bags, and standing bags.

(2). Packaging process.

The vertical form fill sealing machine is a machine that makes the laminated packaging roll films into a bag tube, filling and sealing the bags, the three functions are automatically and continuously completed. The plastic stretch film motor is controlled to pull the packaging plastic film down, and then the transmission part of the stretch film supplies the length of the stretch film according to the signal of the sensor that detects the plastic film. The stretch film is partially formed by the bag former, and seals the bottom of the packing bag horizontally. The next step is automatic weighing and unloading. The material falls into the bag, then seals, and finally cuts off, and a complete packaging bag comes out.

The packaging process of an automatic pre-made pouch fill and seal Machine is:

(1). The operator puts a certain number of pre-made pouches in the place where the machine automatically takes the bags. The bag will be automatically sent to the machine clamp, and the turntable will transport the bag to the coding station. After the ribbon inspection, the packaging machine performs normal coding on the bag.

(2). After the above two processes, the machine clamp will automatically open the packing bag and fill the material in. In this process, the packaging machine will first detect whether the packing bag is opened. If the bag is not opened, the material will not automatically fall.

(3). After the material is filled, the machine can be equipped with exhaust gas, nitrogen gas, and other processes, and then enter the heat sealing process, that is the bag packaging machine will seal the packing bag filled with the material at a set temperature. The last step is The conveyor belt outputs the packed bags.

How to choose this suitable quick-frozen product filling machine? If your quick-frozen product category is relatively single, it is recommended to use the vertical form fill sealing machine. If there are many types of products, it is recommended to use the automatic premade pouch fill and seal machine, because it is suitable for a wide range of bag types, the bag width is different, you can use the same machine to complete filling within a certain range. The adjustment method is also very simple, only need to complete the setting on the touch screen, without any manual adjustment.

We offer a wide range of frozen packaging machines which is depending on your specific needs and requirements. Contact us today for all your frozen food packaging needs！