THE COLD IN THE KITCHEN

FOOD DEGRADATION RULES AND LAWS

Parisi's First Law [1]of Food Degradation establishes and warns that there is no food that could remain unchanged over time; their chemical, physical, microbiological and structural characteristics are always subject to change, without exception and irreversibly. Therefore, every food undergoes an alteration . In other words, all food products are inevitably subject over time to a continuous and unstoppable transformation of their chemical, physical, microbiological and structural characteristics.

Parisi's Second Law of Food Degradation establishes and warns that mechanical processes having the purpose of dividing a food into a series of smaller parts, or mechanical processes (e.g. blending, etc. ) which aim to demolish the structure in some way, cause a decrease in durability compared to the same unworked element without the aid of other conservative treatments. In other words, food durability is destined to decrease in portioned food compared to the same whole food, in identical storage conditions. Therefore, each sectioned food undergoes an increasingly remarkable alteration over time.

The key to microbiological control of hygienic safety as well as microbial growth in foods lies in the knowledge and application of the principles of microbial ecology. And a definition given by Mossel , in 1983.

DEFINITION

Cooling a liquid or gas until it becomes solid: An example is when cold freezes water; In the case of food, bring food to low temperatures.

REFRIGERATION

In the field of food preservation we speak of refrigeration when food is brought to a temperature between 0°C and 10°C. This process slows down, but does not block, the deterioration of food. This means that refrigerated products can be stored for limited periods of time: a few days, a maximum of two weeks.

FREEZING

It is a conservation system that resorts to the use of "subzero cold". Foods are brought to temperatures generally at -18°C and are stored at temperatures of -18°C.

In freezing the freezing times last several hours. These long times allow the formation of larger ice crystals, which can easily damage the cellular structure of foods.

thawing due to the loss of water and the breakage of the cellular structures , especially in foods with a less resistant cellular structure.

Although it is an effective method to lengthen the shelf life of food, freezing does not allow the activity of the enzymes to be blocked 100%, with consequent deterioration of the original quality of the product over time.

These are the main variations and modifications that are found in terms of nutrients:

• Degradation of pigments – degradation of chlorophyll to phaeophthine (rupture of chloroplasts and chromoplasts) and change in the color of anthocyanins (change in pH due to salt precipitation)

• Residual enzymatic activity - For polyphenoloxidase and lipoxygenase due to poor blanching (lipid oxidation, loss of carotenoids , off-flavor and odours ) in meat, there can be proteolytic and lipolytic activity.

• The proteins undergo denaturation which does not, however, involve variations in the nutritional value as this is in relation to the amino acids present. The product becomes more digestible (digestibility increases by 10-40% in the first year of storage and then tends to decrease).

• Fats can easily undergo hydrolysis and oxidation, phenomena which, in addition to negatively affecting the organoleptic characteristics of the product, decrease its nutritional value, especially at the expense of essential fatty acids and polyunsaturated ones (salmon, mackerel, sardines, foods rich in polyunsaturated fatty acids) whose compounds, consisting of peroxides, hydroperoxides and free radicals, can react with proteins giving rise to harmful substances. Lipid oxidation, slower at -18°C

• Carbohydrates undergo a slow hydrolysis process (no loss of quality)

• Mineral salts and water-soluble vitamins are partly lost during the preliminary blaching

• Virtually all foods can be frozen, including ready-to-eat meals. Freezing does not kill most bacteria, it only stops them from growing. The advice is to consume frozen foods within 3-6 months of freezing at home. Food must therefore be consumed within 24 hours of complete defrosting.

The rules for correctly defrosting food

It should be borne in mind that at room temperature bacteria reproduce quickly. For this reason it is advisable to always defrost in the refrigerator for a maximum of 24 hours, in this way the temperature of the product being defrosted will remain controlled and constant and will not increase the microbial load in the food.

The rules for properly freezing food

· Pay attention to the packaging , which is essential to protect the food and prevent it from deteriorating. The best materials on the market for packaging are aluminum, plastic and glass.

· The faster it cools, the better the flavors will be preserved. To facilitate the cooling of cooked foods, the containers to be frozen can be placed in a much larger container, with cold running water or water and ice; in this way the temperature of the food will drop faster than by cooling it at room temperature. After that you can place it in the refrigerator and then move it to the freezer when it is completely cooled down.

· Always label the packages, to remind you of what's inside and the date of preparation. For each type of food there is a different storage time limit, which must be respected, otherwise you will lose nutrients and risk your health.

The rules for food packaging

1. be non-toxic and compatible with the food they come into contact with,

2. give the product adequate sanitary protection, i.e. act as a barrier to the entry of microbes and dirt in general, as well as resisting the attack of insects and rodents,

3. protect against the migration of moisture and possibly grease,

4. prevent the entry (and exit) of gases and odors,

5. protect from light or offer good transparency,

6. resist mechanical trauma, tampering and possibly reveal the latter

7. be easy to open (possibly to close), to use and to dispose of, suitable in size, shape and weight, economical in relation to the value of the contents

FREEZE

Freezing means subjecting foods to a typically industrial process, through which, with special machinery, "fresh" foods are quickly brought to low temperatures, below -18°. This ensures that the ice crystals that form in the food are small and do not affect the cellular structure. In this way the organoleptic and nutritional values (proteins, vitamins, carbohydrates, etc.) and the flavor of the food therefore remain unaltered with respect to the original product. With reference to the frozen product, it is must prevent the product from exceeding the temperature of -18° in all phases, from freezing, to transport, to storage.This is why it is important that the home freezer is able to maintain temperatures lower than or equal to -18°.

Microbial growth takes place in a wide temperature range – 18 °C - + 73 °C.

PSYCHROPHILES grow in a range from – 10 °C to + 20 °C. Cold doesn't necessarily kill them.

Here are some examples and where they can be found:

• Psychrotrophs in pasteurized milk: Bacillus , Enterococcus

• Psychrotrophs in butter and fresh cheeses: Pseudomonadaceae

• Psychrotrophs in fresh meat: Pseudomonadaceae

• Psychrotrophs in fresh meat packaged in a modified atmosphere: Enterobacteriaceae , Enterococcus

• Psychrotrophs in fresh fish: Pseudomonadaceae , Vibrionaceae

• Psychrotrophs in fresh vegetables: Pseudomonadaceae

Many enzymatic processes are only slowed down by the cold. It is customary to interrupt the enzymatic activity before freezing, through blanching (for vegetables, scalding in water or steam 70 °C-105 °C) or with the use of additives, with the exception of preservatives (E200-E299) , prohibited by law in Europe.

It can be stated with absolute certainty that frozen products are hygienically safe since the spoilage microorganisms, responsible for the deterioration of food, and the pathogenic ones, capable of causing infections, intoxications and toxinfections in humans, are not able to reproduce at lower temperatures at -18°C.

This does not mean that the microbes do not return when the product is thawed.

The action of the cold will always and only be bacteriostatic . Does not sterilize.

The factors that regulate the speed of freezing are of various types:

EXTERIORS:

• · Nature of the cooling medium;

• · Coolant temperature,

• · Possible agitation system;

• · Δ T °C (temperature difference) food – cooling medium;

• · Headspace;

• · Packaging (primary packaging);

INTERNAL:

• Food conductivity and density;

• Initial temperature;

• Food area available for heat transfer;

• Size of pieces of food;

INSTALLATION CLASSIFICATION

(based on freezing speed):

• Slow freezers (0.2 cm/h) (cold rooms)

• Fast Freezers (0.5 – 3 cm/h) (forced air and plate)

• Rapid freezers (5 – 10 cm/h) (fluidized bed)

• Ultra-fast freezers (10 – 100 cm/h) (cryogenic) (CO2, N2, air)

Checks

• Presence of frost – The presence of frost around the package may indicate that the product has gone through storage phases at not low enough temperatures, which have allowed the water vapor in the air to create large enough crystals on the outside of the package.

• Blocks of pieces – The presence, inside the product in pieces, of compact blocks, can indicate that there has been a melting and then a re-freezing of the product, which has allowed the creation of agglomerates of pieces.

• Thawing liquids – Especially in meat , the presence of liquids in the package, even frozen, inside the package, may indicate defrosting in one of the manufacturing phases.

The rules for correctly defrosting food

It should be borne in mind that at room temperature bacteria reproduce quickly. For this reason it is advisable to always defrost in the refrigerator for a maximum of 24 hours, in this way the temperature of the product being defrosted will remain controlled and constant and will not increase the microbial load in the food.

TO BREAK DOWN

A blast chiller is equipment used to rapidly reduce the temperature of food from a cooking or storage level to a safe temperature for long-term storage. A blast chiller is nothing more than a freezer which, using forced air at -40 °C. Industrial freezing is very often a different thing, for example in cryogenic freezing.

The blast chiller is a tool mostly used in restaurants and in ice cream parlors and pastry shops. The food maintains its properties unaltered because the bacterial proliferation is blocked by the sudden drop in temperature. The advantage is that foods treated with the blast chiller are safer and keep longer than untreated food.

• Reduce the temperature of cooked foods before freezing them;

• Reduce the temperature of raw foods to avoid health risks;

• Minimize the chances of bacterial contamination of the product;

• Preserve the properties that the food possesses, preventing them from being dispersed over the hours or days;

• Avoid the quick and easy deterioration of food and the consequent waste of money and food

The blast chiller has two most used functions: negative and positive blast chilling. In addition to the two basic functions, the latest generation blast chillers also have functions for leavening, low temperature cooking, pasteurization and defrosting.

The blast chiller and in the professional production of desserts offers various benefits that can be obtained.

Moisture conservation When a freshly baked cake is allowed to cool at room temperature, it tends to dry out. While if it is blast chilled, it retains the humidity inside , making it softer and preserving all its qualities.

Stock of pre-leavened foods Thanks to the blast chiller you can always have pre-leavened or pre -cooked products available for banquets or for special needs and emergencies. Just stop cooking a few minutes earlier and immediately pass the food through the blast chiller. This procedure offers a great opportunity: to work with fresh food as if it had just been made.

The over-run in the preparation of ice cream Air is incorporated during the passage from the liquid to the solid state of the homemade ice cream . This process, called over-run , must be balanced because it is an element that can guarantee the success of the product. In fact, it gives creaminess and lightness: the ice cream thus seems less "cold". Passing the batch freezer tray through the blast chiller, the ice cream preserves the air that was formed previously in a correct and optimal manner.

Using silicon molds Molds can easily be inserted into the blast chiller, which have become increasingly used tools for making cakes, themed biscuits and chocolates. Their resistance to low temperatures makes them not only suitable for blast chilling, but also make extracting sweets simple.

Positive abatement

It allows rapid cooling of cooked foods in about 90 minutes with the internal temperature of the food dropping to 3° at the core . . In fact, with positive blast chilling it is possible to lower the internal temperature of freshly cooked food, bringing it to 3 degrees in about 90 minutes.

The result of this treatment is that the quality of the preserved food is better, as well as the color is more lively. As for the fragrance, the blast chiller allows the food to lose little liquid, which after treatment is cooked fresh.

To blast chill cooked foods, proceed as follows:

Place the food on a tray or other suitable container while still hot in the blast chiller.

Place the probe thermometer at the innermost point of the food.

Wait for the temperature to reach 3°C.

Negative abatement

While with negative blast chilling , which therefore allows freezing, the temperature inside the heart of the food is brought down to -18 degrees in about 240 minutes. The rapidly induced cold acts with a bacteriostatic capacity, preventing bacteria from proliferating. It can also be frozen at -40.

All the advantages of using the blast chiller

1. Food foods keep intact the organoleptic properties and the characteristics of freshness and fragrance

2. Reduces weight loss per serving because less water evaporates

3. Bacterial proliferation is blocked, both of cooked foods and cooked foods with the result that they are safer (see the paragraph on freezing).

4. When foods are frozen, micro crystals form which do not affect the structure and taste. Contrary to what happens in the freezer when frozen

5. The preservation time of the dishes is lengthened, avoiding their easy deterioration

6. Work is speeded up: in fact, a dish can go directly from the oven to the blast chiller

Possession of a blast chiller is not a legal obligation , however it is the blast chilling procedure that is mandatory . In Europe, the EC Regulations 852 and 853 of 2004 on food safety and hygiene indicate how to use the blast chiller.

Establishments that treat and administer raw fish must keep it at a temperature below -20° for a minimum continuous period of 24 hours to eradicate anisakis , a parasite present in fish and dangerous for humans

[1] Salvatore Parisi is an Italian food chemist, with various international awards.