8 Métodos de conservación de alimentos

Introduction to Methods of Food Preservation

In this section, the speaker introduces the topic of food preservation and categorizes foods based on their perishability.

Categorization of Foods

• Non-perishable foods (e.g., sugar, flour, dry beans) do not easily spoil under normal storage conditions.

• Semi-perishable foods (e.g., potatoes, dried fruits) can remain edible for a longer time if handled and stored properly.

• Perishable foods (e.g., meat, fish, dairy products) easily spoil unless special preservation methods are used.

Importance of Food Preservation

The speaker discusses the significance of food preservation and highlights the economic implications of microbial spoilage.

Implications of Microbial Spoilage

• Over 20% of all produced food is lost due to microbial action at various stages.

• Microorganisms can affect taste, produce toxins, deplete nutrients, and transmit diseases.

• Lactobacilli, molds like Aspergillus spp., yeasts, and bacteria are some agents responsible for these actions.

Factors Affecting Food Quality

The speaker explains how both manufacturers and consumers contribute to food quality issues.

Factors Affecting Food Quality

• Manufacturers' actions before commercialization can impact product image and quality.

• Distributors' handling practices and consumers' storage habits also influence food quality.

Definition and Classification of Preservation Methods

The speaker defines preservation methods as treatments that extend shelf life while maintaining quality attributes.

Classification of Preservation Methods

1. Low-Temperature Methods:

• Refrigeration (2-5°C) and freezing slow down microbial growth.

• Maintain color, taste, and nutritional value.

2. High-Temperature Methods:

• Boiling, pasteurization, sterilization, dehydration, and drying use heat to preserve food.

• Eliminate or inhibit microorganisms.

3. Other Methods:

• Fermentation, curing, salting, smoking, and irradiation are preservation methods not solely dependent on temperature.

• Temperature may play a role but is not the primary factor.

Refrigeration as a Preservation Method

The speaker explains the process of refrigeration and its effects on food preservation.

Refrigeration Process

• Refrigeration involves applying cold temperatures without liquid crystallization.

• Domestic refrigerators typically maintain temperatures between 8-15°C.

• Factors like storage temperature, relative humidity, air velocity, and gas composition affect refrigeration effectiveness.

Effects of Refrigeration

• Retards chemical reactions and enzyme activity in food.

• Slows down the growth of mesophilic bacteria that can cause spoilage.

• Rapid cooling can lead to cold shock killing certain bacteria.

Factors Affecting Refrigeration

The speaker discusses factors that influence the effectiveness of refrigeration as a preservation method.

Factors Affecting Refrigeration

• Storage temperature: Lower temperatures enhance preservation.

• Storage space: Proper arrangement allows for better airflow around food items.

• Relative humidity: Higher humidity facilitates cooling efficiency.

• Air velocity: Faster air movement aids in lowering temperature effectively.

• Gas composition: Modified atmospheres with altered gas concentrations can extend shelf life.

Freezing as a Preservation Method

The speaker explains the concept of freezing as a preservation method for food.

Freezing Process

• Freezing involves cooling food until all components reach a temperature below the freezing point.

• The freezing point is not always 0°C due to the presence of substances in food.

The transcript continues, but this summary covers the main points related to methods of food preservation.

Thermodynamic Destruction of Organisms

This section discusses the thermodynamic destruction of organisms, focusing on more complex organisms such as fungi and yeast. It explains that certain parts of these organisms are more sensitive to destruction, while other parts remain unaffected.

Thermodynamic Destruction

• Organisms like fungi, yeast, and sensitive segments are susceptible to destruction.

• Certain parts of the organisms are more sensitive than others.

• The destruction does not affect non-living matter.

Temperature Effects on Reproduction

This section explores the effects of temperature on reproduction. It highlights the significance of temperatures below -10 degrees Celsius in limiting the reproduction of molds and yeasts. It also mentions that some bacteria can still multiply at lower temperatures but at a slower rate.

Effects of Low Temperatures

• Temperatures below -10 degrees Celsius limit mold and yeast reproduction.

• Some bacteria can still multiply at low temperatures but at a slower rate.

• Freezing temperatures can cause transformations in enzymes, altering taste and destroying vitamins.

Freezing Temperatures for Food Preservation

This section discusses freezing temperatures for food preservation. It emphasizes that food can undergo transformations and enzyme oxidation when exposed to freezing temperatures. It also mentions the ideal freezing temperature for preserving food quality.

Freezing Temperatures

• Food can undergo transformations and enzyme oxidation at freezing temperatures.

• Center thermal temperature for frozen products should be -18 degrees Celsius.

Methods of Freezing

This section explores various methods of freezing food. It distinguishes between slow freezing (using chambers with circulating air) and rapid freezing (using tunnels). It also highlights the formation of large ice crystals in slow freezing and the damage caused to cellular walls.

Freezing Methods

• Slow freezing: Chambers with circulating air, freezing at a rate slower than 1 cm/hour.

• Rapid freezing: Tunnels with freezing speeds close to 5 cm/hour, using temperatures between -20 and -35 degrees Celsius.

• Rapid freezing forms microcrystals that damage cellular walls but allow for better moisture retention during thawing.

Ultra-Rapid Freezing

This section discusses ultra-rapid freezing as a method of food preservation. It mentions that ultra-rapid freezing requires higher energy and more sophisticated equipment. Liquid cryogenics, such as nitrogen, are used for ultra-rapid freezing at temperatures below -40 degrees Celsius.

Ultra-Rapid Freezing

• Ultra-rapid freezing is performed in chambers or tunnels with freezing speeds greater than 5 cm/hour.

• Temperatures below -40 degrees Celsius are required.

• Liquid cryogenics like nitrogen are commonly used.

Direct and Indirect Contact Freezing

This section explains direct and indirect contact methods of food freezing. It describes direct contact as submerging the food in a solution or spraying the solution onto the food. Indirect contact involves placing the packaged product between refrigerated plates while spraying it with brine.

Direct and Indirect Contact Freezing

• Direct contact: Food is submerged or sprayed with a solution that does not freeze at the same temperature as water (e.g., brine).

• Indirect contact: Packaged product placed between refrigerated plates while being sprayed with brine.

Considerations for Freezing Process

This section highlights important considerations for the freezing process. It emphasizes the need for fresh food, immediate preparation before freezing, and maintaining a cold chain to prevent contamination and ensure optimal preservation.

Considerations for Freezing

• Only freeze fresh food; avoid freezing food in the early stages of deterioration.

• Prepare food immediately before freezing.

• Maintain a cold chain and store frozen food at temperatures between -18 and -20 degrees Celsius.

Nutrient Loss and Preservation Duration

This section discusses nutrient loss during freezing and the recommended duration for preserving different types of food. It mentions that proteins may lose their quaternary structure when frozen or thawed, while fats can undergo slow oxidation. It also recommends blanching or scalding vegetables and fruits before freezing.

Nutrient Loss and Preservation Duration

• Proteins may lose their quaternary structure during freezing or thawing.

• Fats can undergo slow oxidation during the freezing process.

• Blanching or scalding is recommended for vegetables and fruits before freezing.

• Meat can be preserved for up to 12 months under optimal conditions.

Conclusion

This section concludes the discussion on freezing methods and considerations. It reiterates the importance of maintaining a cold chain, using fresh ingredients, and following proper preparation techniques to ensure successful frozen food preservation.

Final Thoughts

• Maintaining a cold chain is crucial for successful frozen food preservation.

• Use fresh ingredients for better results.

• Follow proper preparation techniques before freezing.

Freezing and Thawing Process

This section discusses the process of freezing and thawing food items.

Freezing Process

• Food items can be frozen for up to six months, with cooked dishes lasting up to four months and bread lasting up to three months.

• When it comes time to thaw frozen food, it is important to ensure that the temperature is consistently above freezing at all points within the food.

• Meats should be thawed slowly in a cool and dry environment, avoiding exposure to air or fluctuating temperatures.

• It is recommended to place a cloth over the meat during thawing to prevent contamination from external sources.

• For larger cuts of meat, a stream of air can be used for thawing, but it should be cleaned frequently with a dry cloth.

High-Temperature Preservation Methods

• Boiling: Food is subjected to temperatures between 95°C and 105°C for varying durations based on the type, structure, and volume of the food item.

• The boiling point varies with altitude; as elevation increases, the boiling point decreases.

• Boiling helps eliminate most of the flora or microbiota found in food but does not provide long-term preservation. Cooked foods can still last 4 to 10 days depending on storage conditions.

Pasteurization

• Pasteurization involves heating food items at high temperatures for a short period of time.

• It effectively kills enzymes and vegetative forms of microorganisms but may not eliminate spores.

• Pasteurized products can be further preserved through refrigeration or freezing methods.

Commercial Sterilization

• Commercial sterilization refers to heating food items at temperatures above 100°C for variable durations depending on the quality, texture, consistency, and fragility of the product.

• The goal is not complete sterilization but rather reducing pathogens and ensuring the product is safe for consumption.

• The packaging must be vacuum-sealed to maintain quality and prevent recontamination.

Sterilization Methods and Considerations

This section explores sterilization methods and considerations for different types of food items.

Commercial Sterilization

• Commercial sterilization involves heating food items at temperatures above 121°C under pressure for 15 minutes or more.

• It aims to eliminate pathogens and reduce spoilage organisms, but complete sterilization may not be achieved.

• Products suitable for commercial sterilization include acidic ones like pickles and guava, while low-acid vegetables may require other preservation methods.

Dehydration

• Dehydration refers to reducing the water content of food items by at least 13% through exposure to hot air.

• This artificial technique helps preserve food by inhibiting microbial growth.

Conclusion on Preservation Methods

This section concludes the discussion on various preservation methods.

Summary of Preservation Methods

• Freezing and thawing are effective for preserving cooked dishes, bread, and other food items.

• Boiling helps eliminate most microorganisms but does not provide long-term preservation.

• Pasteurization kills enzymes and vegetative forms of microorganisms but may not eliminate spores. Refrigeration or freezing can further extend shelf life.

• Commercial sterilization aims to reduce pathogens but does not guarantee complete sterility. Vacuum-sealed packaging is crucial for maintaining quality.

• Dehydration reduces water content in food items, inhibiting microbial growth.

The transcript provided was in a language other than English. The summary has been translated into English based on the given transcript.

Effects of Drying on Food

This section discusses the effects of drying on food, including the damage to certain nutrients and the increase in protein digestibility.

Effects of Drying on Nutrients

• Drying can lead to the damage of nutrients such as humic acids, carotenoids, and fat-soluble vitamins.

• Thiamine (vitamin B1) can be destroyed during the drying process.

• Proteins may decrease in their biological value but become more digestible depending on the drying method used.

Traditional Drying Methods

• Sun drying involves placing vegetables or meat on trays exposed to sunlight. It is important to cover the food to prevent contamination from dust.

• Freeze-drying is a specific method that removes almost all liquids from food at temperatures below -10 to -40 degrees Celsius and low pressure. Frozen products are dried at temperatures below -18 degrees Celsius without thawing.

Sublimation Method

• The sublimation method, developed in the early 20th century, allows some solvents to pass directly from solid to gas state similar to dry ice.

• This method was initially used for preserving bacteria, viruses, and other microorganisms in healthcare settings but later found applications in food production.

Advantages of Drying Methods

• By removing moisture, dried products can be easily stored and transported with reduced weight.

• Constant temperatures inhibit microbial growth as microorganisms require water for their metabolism.

• Rehydrating dried foods restores their original properties by adding back water.

Fermentation as a Preservation Method

This section explores fermentation as a preservation method and its cultural significance in different regions.

Fermentation Process

• Fermentation involves transforming sugars into acids through the action of microorganisms.

• Sodium chloride (salt) is commonly used to control the growth of harmful bacteria and prevent putrefaction during fermentation.

• Fermentation can be carried out by bacteria, yeast, or a combination of both.

Traditional Fermented Products

• Fermentation has been used for centuries to produce various foods and beverages such as bread, wine, vinegar, beer, cheese, and pickles.

• These traditional methods have cultural significance and contribute to the unique flavors and qualities of the products.

Curing as a Preservation Method

This section discusses curing as a preservation method using curing salts and its impact on food properties.

Curing Process

• Curing involves the use of curing salts like sodium nitrite/nitrate to modify pH levels and inhibit bacterial growth.

• Curing agents such as salt, sugar, sodium nitrite/nitrate, and vinegar alter the color, aroma, texture, and microbial stability of cured meats.

Examples of Cured Meats

• Ham is one of the most well-known cured meats. There are various types of ham produced using different curing methods.

The transcript does not provide enough information for further sections.

Different Methods of Meat Preservation

This section discusses different methods of preserving meat, including curing with a mixture of ingredients or directly adding curing agents to the ground meat. Salting dehydrates the food and inhibits the growth of microorganisms. The concentration of salt affects the growth of microorganisms, which depends on factors such as pH, temperature, protein content, and water presence.

Curing with Salt

• Salting dehydrates the food through osmosis by equalizing the concentrations of solutions on both sides of cell membranes.

• Microorganisms in meat can contain up to 80% water and are affected by salting.

• Bacteria and microorganisms cannot survive in a highly concentrated saline solution (30-40% weight).

• Salting can be done either by dry salting or brining in a saltwater solution.

Smoking as a Preservation Method

• Smoking is an ancient preservation method practiced since ancient Egypt.

• It modifies the appearance, color, odor, and flavor of the food.

• The temperature during smoking varies between 43°C and 71°C.

• Different types of wood can be used for smoking to impart specific flavors.

• Smoke contains chemicals like formaldehyde, phenols, acetic acid, and pyrones that inhibit microbial growth and fat oxidation.

• However, some compounds produced during smoking are carcinogenic.

Irradiation as a Preservation Method

• Irradiation involves applying ionizing radiation to food for a certain period.

• Doses are measured in grays (Gy), where 1 Gy is equivalent to absorbing one joule of energy per kilogram of mass.

• Irradiation can stabilize parasites like trichinae spiralis in pork or cysticerci in solid cane sugar.

• It retards fruit ripening and extends shelf life by inhibiting the ripening process.

• Different doses of irradiation can be used, depending on the desired effect and the type of food.

Combination of Preservation Methods

• Combining irradiation with other preservation methods can enhance their effectiveness.

• Each method has its limitations, so combining them can provide better preservation results.

Irradiation for Food Preservation

This section focuses on the method of irradiation for food preservation. It explains how irradiation works, its applications, and the different doses used for specific purposes.

Irradiation Process and Parameters

• Irradiation involves applying ionizing radiation to food.

• The parameters to consider include temperature, packaging, presence of oxygen, and selecting appropriate doses.

• Combining irradiation with other methods can overcome certain obstacles in food preservation.

Types of Irradiation Treatments

1. Radicidation:

• Equivalent to commercial sterilization.

• High doses (30-40 kilograys) reduce the number of viable pathogens to undetectable levels by conventional methods.

2. Radurization:

• Equivalent to pasteurization.

• Low to medium doses (2.5-10 kilograys) reduce the number of spoilage microorganisms while maintaining product quality.

3. Radappertization:

• Used for canned foods.

• Moderate doses (2.5-3 kilograys) achieve a considerable reduction in specific spoilage microorganisms.

Factors Affecting Irradiation Preservation

• Temperature during treatment

• Type of packaging

• Presence or absence of oxygen

• Combinations with other preservation methods

Air Conservation through Radiation Method

This section discusses air conservation through radiation as a method for preserving fruits and vegetables. It explains the importance of selecting parameters such as temperature, packaging, and oxygen levels for effective preservation.

Air Conservation through Radiation

• Irradiation can be used to preserve fruits and vegetables.

• Parameters to consider include temperature, packaging, and the presence of oxygen.

• Combining irradiation with other methods can enhance preservation results.

Conclusion

In this transcript, we learned about different methods of meat preservation, including curing with salt and smoking. We also explored the use of irradiation as a preservation method for various types of food. Each method has its advantages and limitations, but combining them can provide better results in terms of food safety and shelf life extension. The selection of parameters such as temperature, packaging, and oxygen levels is crucial for effective preservation using irradiation or other methods.

Packaging and Vacuum Sealing

This section discusses the process of vacuum sealing and its benefits in food packaging.

Vacuum Sealing and Air Extraction

• Vacuum sealing involves extracting air from food packaging.

• Different types of packaging are used, including rapid cooling after cooking.

• Modified atmospheres can be created using combinations of gases like nitrogen, carbon dioxide, or oxygen.

• Vacuum sealing extends the shelf life of products by minimizing exposure to air.

Heating and Sterilization

• Foods can be heated inside their packaging using autoclaves or tunnels.

• Autoclaves with mobile agitators reduce heating time for liquid or semi-liquid foods.

• Pasteurization is done using hot water sprays in tunnels for cans, bottles, and jars.

• The temperature can be adjusted based on the desired outcome.

Cooling and Pressure

• The cooling process relies on atmospheric pressure.

• Water sprays or atomized water are used to cool down the packaging system.

• Atmospheric pressure plays a role in postulating methods.

Heating Methods

This section focuses on different heating methods used in food processing.

Autoclaves and Agitators

• Autoclaves with mobile agitators reduce heating time for cans containing liquid or semi-liquid foods.

Tunnel Pasteurization

• Tunnels are used to pasteurize foods and beverages packaged in cans, bottles, and jars.

• Hot water sprays or atomized water are employed to achieve the desired temperature.

Cooling Methods

This section explains the cooling methods utilized in food processing.

Cooling with Atmospheric Pressure

• The cooling process depends on atmospheric pressure.

• Water sprays or atomized water are used to cool down the packaging system.

Postulating Methods

• Atmospheric pressure is one of the methods employed for postulating food products.

The transcript provided does not specify the language, so the notes are written in English.