تكنولوجيا الغذاء والأساليب العلمية

Food Technology

• Food technology is the application of food science to the selection, preservation, processing, packaging, distribution, and use of safe, nutritious, and wholesome food.
• Food science is the discipline that studies the nature of foods, the causes of their deterioration, and the principles underlying food processing, utilizing biology, physical sciences, and engineering.
• Quality is a composite of cost and quality. More expensive foods can be a good value if their quality is high.
• Nutritional quality, sensory quality, and keeping quality are factors that are often not apparent by sensory observation.
• Nutritional quality can be assessed by chemical or instrumental analyses for specific nutrients.
• Sensory quality is divided into three categories: appearance, textural, and flavor.
• Sanitary quality can be measured by counting bacteria, yeast, mold, and insect fragments, as well as sediment levels.
• Keeping quality, or storage stability, is measured under storage and handling conditions that simulate or slightly exceed the normal distribution and use conditions.

Food Preservation and Storage

• Food is essential for human life and health. Most food products are seasonal and spoil quickly.
• Foods deteriorate or spoil from the time of harvest, catch, slaughtering, or manufacturing unless preserved. The preservation process prevents the loss of quality, edibility, and nutritive value.
• Knowledge of processing and preservation methods is crucial for producing best possible foods over an extended period with minimal loss of nutritive value.
• The preservation of raw and processed food products are a key factor in the shelf life of food.

Definition of Food Storage

• Food storage is the process of preserving cooked and raw ingredients in suitable conditions for future use.

Types of Storage

• Basic storage types include dry storage and low temperature storage.
• Dry storage is designed for non- and semi-perishable foods at room temperature.
• Low temperature storage includes refrigerated, cold, and freezer storage based on the temperature ranges and holding times.

Essential Features of Food Storage Areas

• Storage areas must be suitable for the specific food product that needs to be stored.
• Areas must be separated to prevent cross contamination.
• Protection from contamination/infestation is essential.
• Storage areas must be weatherproof.
• Direct sunlight/heat should be blocked.
• Sufficient light and ventilation are needed.
• Storage areas must be easily cleanable.
• Easy transport of stored materials is essential.

Storage life of Some Foods (Table 1)

• A table showing the expected storage life of various foods at room temperature.

Food Spoilage

• Healthy tissues in foods help resist infection and microbial growth.
• Spoilage happens due to poor sanitation, enzymatic/chemical reactions, improper temperature control, microbial growth, and physical abuse starting from the time of harvest, slaughtering, and manufacturing to consumption.
• It refers to undesirable alterations in food or changes in the physiological, chemical, and biological processes that lower the quality and safety of the food products.

Factors Affecting Food Spoilage

• Food composition influences susceptibility to spoilage (e.g., proteins and sugars).
• Food structure—healthy inner tissues are sterile or low in microbes, while skin, etc. provide a protective barrier.
• Types of microorganisms present in food depend on its composition.
• Storage conditions affect microbial growth. Improper storage lowers the quality and nutritive value of food.

Classification of Foods by ease of Spoilage (Perishability)

1. Relatively stable or non-perishable foods: These foods do not spoil easily if handled carefully (grains, flour, sugar, pulses).
2. Protectable or semi-perishable foods: These foods remain unspoiled for a long time with proper handling and storage (potatoes, apples, onions).
3. Perishable foods: They spoil quickly without preservative methods (milk, eggs, meat, fish).

Causes of Food Spoilage

1. Biological: Growth and activity of microorganisms (bacteria, yeasts, molds).
2. Chemical: Reactions with oxygen, light, and within food constituents.
3. Physical: Temperature changes (freezing, burning, drying), physical abuse.

Sources of Microorganisms in Food

• Soil and water
• Plants and plant products
• Food utensils
• Intestine of animals
• Food handlers
• Animal hides and skins
• Air and dust

How does Food Processing Influence Spoilage Rate?

• Increased microorganisms during processing.
• Normal spoilage flora destruction and new microflora introduction.
• Changes in intrinsic and extrinsic food parameters.

Bacteria

• Bacteria are more difficult to kill than molds and yeasts.
• They are present in vegetative and spore forms.
• Vegetative forms are easily destroyed at boiling temperatures.
• Spores require harsh treatments like high heat or pressure for long durations.
• Bacteria are classified as aerobic, anaerobic, and facultative based on oxygen needs.
• Based on temperature requirements for growth, they can be grouped into mesophiles, obligate thermophiles, facultative thermophiles, and psychrophiles.

Yeasts

• Yeasts require less moisture and acidic pH to grow.
• Most yeasts do not grow in high sugar or acidic content.

Molds

• Molds are multicellular filamentous fungi.
• They have fuzzy or cottony appearance.
• They grow well in wide pH ranges.
• They produce mycotoxins (toxic substances).

Degradation Processes by Microorganisms

• Putrefaction (degrading proteins).
• Fermentation (degrading carbohydrates).
• Rancidity (degrading fatty foods).

Food Poisoning vs. Food Spoilage

• Food poisoning: Consumption of contaminated food. Microorganisms produce toxins.
• Food spoilage: Spoiled food affects the food's quality.

Factors Affecting Microbial Growth in Food

• Intrinsic factors (inherent in food): pH, moisture content, nutrient content, antimicrobial substances, biological structures, oxidation-reduction potential.
• Extrinsic factors (external to food): Temperature of storage, presence and concentration of gases, relative humidity.

Additional notes

• Tables are provided to summarize different data and parameters.