GID506E

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GID506E

• FOOD STABILITY
• Assis.Prof. Meral KILIÇ

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Food Stability

• Stability equilibrium
• thermodynamic equilibrium
• one phase, minimal free energy
• if two or more phase, chemical potential is
  equal in every part of the system
• chemical potential determines whether a change
  in the system will occur
• molar free energy at constant T and P

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Food stability

• metastable equilibrium
• pseudo-equilibrium, apparent equilibrium
• stable over practical time periods
• when the activation energy to a more stable
  equilibrium state is very high
• rate of conversion is negligible

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Food stability

• Foods are not at thermodynamic equilibrium
• not desired , poor quality
• maximize the number of desirable attributes
  existing in metastable equilibrium
• achieve acceptable stability for other desirable
  attributes that unavoidably exist in a
  nonequilibrium state.

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How to achieve stability

• Change the product composition
• Control process and storage conditions

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Food Quality

• The combination of attributes or characteristics
  of a product that have a significance in
  determining the degree of acceptability of the
  product to the user.
• Food safety
• Stability Keeping quality
• Sensory quality
• Nutritional quality

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Factors affecting food quality

• Intrinsic factors to the food
• Physicochemical characteristics
• Ingredients
• Processing
• Storage conditions

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Factors affecting food quality

• Extrinsic factors
• Attitudes
• Expectations
• Social and cultural influences
• Price
• Convenience
• Brand image

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How to measure quality?

• Quality perception
• Expert vs. Consumer
• Acceptability (perceived quality)
• Degree of excellence
• Deviations from a standard

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How to measure quality?

• 1. Sensory analysis
• 2. Instrumental analyses
• - Chemical (nutrient, compound, GC, HPLC, NMR,
  IR)
• - Physical (texture, Instron, TPA, rheometer)
• - Microbial (spoilage organism)

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Sensory analysis

• 1. Sensory analysis
• Judge
• Consumers Acceptability
• Experts Difference from a reference
• Attributes
• Taste, odor, vision, sound, texture
• Qualitative
• Quantitative intensity

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Sensory analysis

• Storage stability
• Difference tests difference from reference
• too sensitive to small changes
• need to have a good control, not practical
• Descriptive tests quantification of changes
• can compare value with a critical limit
• Acceptance tests hedonic tests
• expensive

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Analysis

• Sensory analysis is subjective, time consuming,
  need extensive training
• Instrumental analysis more reliable
• Electronic nose
• volatile flavor profile
• specific compound

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Modes of Food Deterioration

• Moisture/water vapor transfer
• Chemical/biochemical changes
• Light-induced changes
• Microbiological changes
• Temperature-affected changes
• Other mechanisms/damages

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Moisture/water vapor transfer

• Between product and environment
• Texture defects
• fresh vegetables wilt
• cookies, biscuits, breakfast cereals become soft
  and soggy
• freezer burn in frozen meat products
• Flavor defects
• Microbial growth

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Chemical/biochemical changes

• Rancidity
• 1. Hydrolytic/lipolytic
• lipase
• lipids free fatty acids, off-flavors
• 2. Oxidative
• nonenzymatic autoxidation, free radical
  initiated, metal ion, heat, light catalysis,
  sensitizers
• enzymatic lipoxygenase PUFA -gthydroperoxides
• off-flavors
• chocolate, meat products, dairy products
• loss of color, vitamin degradation, protein
  degradation

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Chemical/biochemical changes

• Maillard browning
• pH, T, aw dependent
• aldehyde (reducing sugar) amine (aminoacid)
  dark colored polymers
• color degradation, loss of protein solubility,
  bitter flavors, lysine loss
• dehydrated fruits and vegetables

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Chemical/biochemical changes

• Chemical hydrolysis degradation of aspartame in
  diet drinks, loss of sweetness
• Product/packaging interactions
• canned foods dissolution of tin into
  intermediate acid (4-5.5) foods in unlacquered
  cans, toxic

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Light-induced changes

• Intensity, wavelength, duration of exposure, T,
  oxygen availability, presence of sensitizers
  (riboflavin, chlorophyll)
• fresh milk under sun, cardboard-like flavor
• butter in nonfoil packaging under fluorescent
  light, oxidative rancidity, photooxidation
• riboflavin, ascorbic acid, folic acid, vitamin
  D, K activity
• reduction
• betanin, chlorophyll poor light stability

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Microbiological changes

• moisture, raw material, contamination
•        pH, aw, acidity, preservatives, nutrients,
  natural microflora, redox potential
• processing technique, chemical and physical
  environment, headspace gas composition, storage
  RH-T
• food spoilage
• visual growth, textural change, fermentation,
  flavor change, color change
• food poisoning
• maybe fatal without visible signs of growth
• intoxication toxin production
• infection contamination and colonization in the
  gut

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Temperature-affected changes

• Temperature-affected changes
• temperature fluctuations
•      condensation, microbial growth
•      fat bloom, white haze on chocolate,
  crystallization of triglycerides
• ice recrystallization in ice cream
• accelerate changes

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Other mechanisms/damages

• spoilage by rodents, birds, insects
• damage pack and exposure of product to
  environment and contamination
• gradual degassing of carbonated beverages
• undesirable odor and flavor due to volatile
  penetration such as paint or chlorine
• migration of plastic material from package into
  food
• product damaging due to mishandling, loss of
  protective vacuum

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What is shelf life?

• Time period for food to be
• Safe
• Stable
• Nutritional
• Chemical
• Physical
• Microbiological

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Who are involved?

• Growers
• Other raw material suppliers
• Manufacturers
• Distributors, wholesalers
• Retailers
• Consumers

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Factors influencing shelf life

• Intrinsic factors
• Raw materials
• Product formulation and composition
• Product make-up
• Water activity
• pH and acidity
• Oxygen availability and redox potential
• Glass transition temperature (Tg)

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Factors influencing shelf life

• Extrinsic factors
• Processing
• Hygiene
• Packaging materials and system
• Storage, distribution and retail display

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Shelf Life Determination

• initial shelf life study
• preliminary shelf life determination
• confirmatory shelf life determination
• routine shelf life determination

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Shelf life determination

• Identification and assessment of food safety
  hazards
• Assessment of the mechanism/mode of deterioration
• Designing the shelf life study
• Sample preparation and storage simulation

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Shelf life tests

• Sensory evaluation
• Microbiological evaluation
• Chemical analysis
• Physical analysis

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Shelf life determination

• Accelerated shelf life determination

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Classification of foods according to shelf life

• Susceptibility to spoilage
• assuming proper packaging and storage conditions
• Perishable foods
• Semi-perishable foods
• Long shelf-life foods

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Shelf life

• Sell by date
• Perishable foods
• Use by date (Expiration date)
• Perishable foods
• Best if used by date (Best before date)
• Semi-perishable and long shelf-life foods

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Shelf life

• High quality shelf life
• Sensory analysis
• Just noticeable difference
• Practical shelf life
• Acceptability
• PSL 2-3 x HSL

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Labeling

• Turkish Food Codex
• lt 3 months day and month Use by
• 3-18 months month and year Best before
• gt 18 months year Best before
• Codex Alimentarius Commission
• lt 3 months day and month
• gt 3 months month and year

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Labeling not required for

• Fresh fruits and vegetables, including potatoes
  which have not been peeled, cut or similarly
  treated
• Wines, liqueur wines, sparkling wines, aromatized
  wines, fruit and sparkling fruit wines
• Beverages containing 10 or more by volume of
  alcohol
• Bakers or pastry-cooks wares which, given the
  nature of their content, are normally consumed
  within 24 hours of their manufacture
• Vinegar
• Food-grade salt
• Solid sugars
• Confectionery products consisting of flavoured
  and/or colored sugars
• Chewing gum.