Food Preservation Techniques

Food Preservation

• Food preservation is crucial for human sustenance
• Understanding food preservation methods, their origins, and influencing factors is important

Definition of Altered Food

• According to the Spanish Food Code, altered food undergoes unintentional changes during sourcing, preparation, handling, transport, storage, or possession
• These changes affect organoleptic properties, chemical composition, or nutritional value, diminishing or nullifying its suitability for consumption while remaining harmless

Factors Influencing Food Preservation

• Conserving food depends on physical, chemical, environmental, and cultural factors
• Preserved food has undergone suitable treatments to maintain hygienic-sanitary conditions for a variable period

Shelf Life

• Shelf life refers to the duration between manufacture and significant changes in a product

Variation in Food Preservation

• Food preservation can be limited and dependent on: food nature, production, storage duration, microbiological, sensory, or physicochemical changes, and packaging
• These factors may affect a food shelf life

Food Classification by Alteration

• Perishable foods:
  • Have very short shelf lives (hours to days), decomposing quickly due to microbial or enzymatic deterioration
  • Require specific packaging and storage, maintained at refrigeration or freezing temperatures with a shelf life of up to 30 days
• Semi-perishable foods:
  • Contain natural inhibitors or undergo minimal preservation treatments for tolerance to environmental conditions and distribution abuse
  • Shelf life ranges from 30 to 90 days and examples include roots, tubers, grains, nuts, rice, raisins, and dried fruits
• Non-perishable foods:
  • Stable at room temperature, with long durations due to low water activity
  • Maintain structure, quality, and durability under correct ambient conditions, with a shelf life from several months to years
  • Examples include canned goods, pastas, dried legumes, sugar, honey, salt, oil, coffee, nuts, seeds, sterilized products, chemically preserved items, dehydrated goods, or properly packaged items

Factors Affecting Food Alteration

• Identifying and listing factors affecting the alteration rate and degree of food products is fundamental, influencing shelf life
• These factors are classified as intrinsic, extrinsic, and implicit

Intrinsic Factors

• Intrinsic factors constitute a product characteristics and can depend on the: type, quality of raw materials, formulation, and composition
  • Includes pH, nutrients, food structure, antimicrobial agents, culinary treatment as it can modify the initial flora

Extrinsic Factors

• Extrinsic factors derive from physical conditions of the storage environment
  • Includes processing, hygiene protocol, handling, packaging materials, storage, distribution, and sales locations

Implicit Factors

• Implicit factors comprise the relationships between microorganisms, resulting from factors a and b

Receiving Area

• The receiving area is where the culinary space begins and leads to product preparation
• Implementing good hygiene and food handling practices is essential once the product is controlled
• This area receives raw materials administered by suppliers, usually with a quality control dock for loading, unloading, and transport vehicle access
• Integrity of food organoleptic characteristics, proper hygiene, and correct labeling (traceability) should be ensured before acceptance
• Equipment includes tables, benches, merchandise weighing scales, transport carts, sinks, trash cans, computerized entry logging, labelers, and thermometers for food monitoring

Storage Zone

• The storage zone is intended for raw materials from the receiving area and semi-processed/finished foods from the climate-controlled preparation area
• This section is divided by conservation thermal characteristics with three store types

Storage Types

• Dry goods & preserves storage:
  • For foods not requiring refrigeration
  • Temperature between 15-18°C with dryness and good ventilation, divided into general storage, daily storage, and beverage storage
  • Usually equipped with shelves, benches, hoppers for food, and ingredient containers
• Refrigeration units:
  • For foods needing cold conditions (0-4°C, prevents freezing)
  • Different food types are stored separately to avoid cross contamination and odor transfer
• Freezing units:
  • Maintains food temperatures between -18 to -20°C

Food Preservation Methods

• These methods prevent food deterioration and prolong the shelf life of food products
• Classified into physical and chemical treatments

Physical Treatments

• Physical treatments include cold, heat, irradiation, and water content modification

Chemical Treatments

• Chemical treatments destroy or inactivate agents causing deterioration

Cold preservation

• It lowers temperatures to reduce the rate of chemical, metabolic, and microbial processes
• This process retards the organoleptic changes during food storage
• Microorganisms may still survive and therefore, maintaining the cold chain is important

Methods of Cold Preservation

• Refrigeration:
  • Short-term (recommended no more than 15 days for most)
  • Uniform temperature without fluctuations is required alongside appropriate temperature for each food
  • Variations in humidity can increase microbial growth. Packaging influence is important
• Freezing:*
  • Long-term preservation by converting water into ice crystals at below -18°C, reducing both food temperature and water activity, categorized into three types

Freezing Types

• Slow freezing:
  • Used for large products, maintains flavor, odor, and quality, requires longer freezing in high-capacity chambers (example: bovine, pork, lamb)
• Medium freezing:
  • Air tunnels at 20 km/h and -40°C, freezing rate of 1-5cm/h
• Rapid freezing:
  • Used in food industry and professional kitchens, quickly cools to prevent bacteria proliferation, 4 hours at -18°C

Heat Preservation

• Heat application reduces or eliminates the action of microorganisms and enzymes
• Accomplished through processes like sterilization and blanching

Heat Preservation Methods

• Sterilization:
  • Destroys all forms of microorganisms (pathogenic or non-pathogenic) at adequate temperatures, applied once or by tyndallization
  • Required when long-term preservation is needed
  • Can decrease some product sensory properties
  • For liquids it is known as UHT, where temperatures of 135-150°C are applied for 4-15 s
• Blanching:
  • Involves exposing food to 95-100°C temperatures for a few minutes
  • Commonly used for fruits, vegetables, crustaceans, and poultry, as a preliminary cleaning, elimination of inedible parts before conservation
  • Three Types include hot water, steam and chemical

Types of blanching

• Hot water blanching:
  • The food is submerged in hot water at 85-98°C
• Steam blanching:
  • The food is exposed to live steam
• Chemical blanching:
  • Employed when prior methods severely damage food, like figs or strawberries

Pasteurization

• Pasteurization conserves by eliminating spoilage microorganisms
• It increases the food temperature, then cools to destroy microorganisms
• There are two processes: low (60-65°C for 3-4 hours) & high (75-90°C for 2-5 min) temperatures

Reducing Water Activity

• Most microorganisms need a liquid environment to proliferate
• Decreasing water activity prevents proliferation accomplished using various methods

Methods of reducing water activity

• Desiccation:
  • Reduces food moisture until it equals the humidity of the environment
• Dehydration:
  • Completely eliminates water, establishing microbiological stability by removing all free water in the food

Concentrations

• Concentrations eliminate water from liquid foods to minimize water activity, thus avoiding microbial growth
• Concentration happens via: evaporation, and congelation

Methods of concentrations

• Evaporation:
  • The oldest method
  • Water removal by heat application until reaching desired solute concentration
  • Applied in dairy product and fruit juice elaboration
• Congelation:
  • Accomplishes a temperature drop to initiate part water crystal generation that results in concentrates with pure ice crystals
  • These extract afterwards, yielding a liquified, concentrated solution
  • Applied in vinegars, orange juice, and sugar based extracts
• Reverse Osmosis and Ultrafiltration:
  • Method uses water permeable membrane with set caliber for selective molecule passage
  • Applies to juice, drinks, milk, and many other products
• Azeotropic Dehydration:
  • Current process for fruit concentrate by combining suitable solvent for water bonding
  • The azeotrope is separated to remove the solvent excess

Lyophilization

• It is where moisture is removed by ultra-freezing and drying
• It can be rehydrated to have the same characteristics, and contains 2% water

Food Irradiation

• Some radiation is applied to foods to destroy/inactivate microorganisms with three methods

Types of irridiation

• Gamma rays:
  • Great penetration in food and reaches 1 meter deep
• Electron beam:
  • Wide spread use but currently desused
• X-rays:
  • Broad application in foods and is the most recent

Chemical Preservation Methods

• Uses chemical preservatives to protect food

Methods without organoleptic modification:

• Chemical preservatives are defined as substances added to food products to protect them from biological alterations
• To lengthen the product shelf lift of the product

Methods with organoleptic modification

• The food subjected to chloride effects acting on testure
• Also helps with the baceteria to avoid a contaminated product
• Helps to keep safe the final product

Explore the importance of food preservation for human sustenance. Learn about the definition of altered food according to the Spanish Food Code. Discover the physical, chemical, environmental, and cultural factors that influence food preservation and shelf life.