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Summary of Alex Lectures Mid-term exam FISH 261 – Spring 2012

Summary of Alex Lectures Mid-term exam FISH 261 – Spring 2012. Fish and shellfish as food. Important things to know : Different from other animal proteins (primarily in muscle structure) Specific texture attributes (muscle texture) Limited shelf life (fish and shellfish spoil v. fast)

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Summary of Alex Lectures Mid-term exam FISH 261 – Spring 2012

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  1. Summary of Alex LecturesMid-term examFISH 261 – Spring 2012

  2. Fish and shellfish as food Important things to know: • Different from other animal proteins (primarily in muscle structure) • Specific texture attributes (muscle texture) • Limited shelf life (fish and shellfish spoil v. fast) • Hundreds of fish and shellfish (to a lesser extent) species with different characteristics and nutritional benefits

  3. Fish and shellfish as food Important things to know: • The fat in fish can be very high in omega-3 fatty acids (e.g. Pacific salmon = sockeye, chinook, coho, chum, and pink) • Consumption Related to Prevention of Coronary Heart Diseases • Seafood has balanced amino acids make up and high protein content (healthy + nutritious) • Shellfish tends to have high sterol levels, mainly cholesterol (e.g. shrimp)

  4. What is in fish muscle? • Water and fat usually combine for 80% of the total composition of fish muscle • Water and fat are interchangeable, that is, higher fat content lower water content and vice-versa • Proteins are the building blocks of living organisms • Fats (lipids) are the primary energy source for living organisms • Fats in terrestrial animals are VERY DIFFERENT from the fats found in marine animals

  5. Major components of seafoods • The three major components of fish and shellfish are: • Water • Protein • Lipids (fat) • These three types of compounds make up as much as 95% of the total gross composition of fish and shellfish • Average composition of fish muscle Water ~ 75% Protein ~ 15% Lipids (fat) ~ 5% Ash (minerals) ~ 5%

  6. Water • Free water: is lost during freezing/thawing, muscle storage and handling • Bound water: is not easily lost (~4-5% of the water in a muscle food) • Water is critical to: • processing characteristics • texture • nutritive value • sensory quality • shelf life

  7. Crude Protein • Crude protein refers to the total of nitrogen containing compounds in a sample. • Muscle proteins are of three classes: • Water soluble proteins: found in abundance in the extra cellular fluid (between cells). Make up ~ 30% of total protein in fish muscle • Salt soluble proteins: make up the "flesh" and are ~ 40-60% of the total protein in fish muscle (muscle cells) • Collagen: make up 3% of total protein in fish muscle (connective tissue – ‘cement’, ‘glues’ muscle cells together)

  8. Lipids • Lipid content of fish muscle refers to the total amount of the following compounds: • Phospholipids – important constituents of cell membranes (STRUCTURAL LIPIDS) • E.g. Lecithin • emulsifying agent used in the food industry (e.g. ice cream) • Sterols – in fish mainly in the form of cholesterol; however, in mollusks and shellfish a wide variety of ‘sterols’ are present (cholesterol is related to proper growth and overall health)

  9. Lipids • Triglycerides (TAG) - main source of energy in fish - FAT • TAG are mainly stored in the liver of fish classified as lean • Fatty fish have TAG reserves mainly in their muscle and belly flap area • Wax esters – used for buoyancy and found in large quantities in deep water fish; present in fish scales (waxes) • E.g. Bee wax is composed of wax esters

  10. Importance of lipids in human nutrition • Lipids (“fats”) are an important source of metabolic energy (calories) • Calories in fat are little over twice the amount of calories found in proteins and carbohydrates (sugars) • Fats supply twice the ENERGY!!! • Essential vitamins such as A, D, E and K are only found in the ‘fatty tissue’ (fat soluble only) • Fat provides the ‘essential fatty acids’ of the types: • Omega -3 fatty acids (w-3 FA) • Omega -6 fatty acids (w-6 FA) • Omega -9 fatty acids (w-9 FA)

  11. Dark vs. White Muscle • Distribution and amounts of dark muscle are different among fish species Sections through the bodies of several fish showing depth of dark muscle. (a) Herring; (b) Mackerel; (c) Tuna; (d) Haddock; (e) Cod; (f) Whiting. Source: Love, 1988

  12. Calories in Fat, Protein and Carbohydrates 1 g Fat = 9 Cal 1 g Protein = 4 Cal 1 g Carbohydrates (sugars) = 4 Cal

  13. http://www.naturalalaskasalmonoil.com/ Produced in Juneau Alaska

  14. Fats: Terrestrial vs. marine animals • Omega-6 and omega-9 fatty acids are most abundant in terrestrial food sources • Omega-3 and omega-9 fatty acids are most abundant in marine food sources • Omega-3 fatty acids (long chain ones) are NOT found in the terrestrial sources at quantities that allow for maintenance of good health!!! • Cholesterol levels in terrestrial animals tend to be higher then in marine animals • Some exceptions are shrimp and crab

  15. Essential vitamins in fish lipids • Fat soluble vitamins • A (retinol) involved in growth and differentiation of tissue, also involved in good eye sight • D (cholecalciferol) required for calcium absorption and retention of bone • E (tocopherol) powerful antioxidant • K (menaquinones) involved in blood clotting NOTE: fats provide the only natural dietary source of vitamin A and of vitamin E Remember: ‘ADEK’

  16. Human Senses • Many accepted definitions • Senses are the physiological methods of perception • Aristotle – There are five senses in humans: • Sight • Hearing • Touch • Smell • Taste http://en.wikipedia.org/wiki/Senses

  17. Human Senses • Smell or olfaction • This is a “chemical" sense • Unlike taste, there are hundreds of olfactory receptors in our olfactory epithelium (where the receptor are located) • Odor molecules have a variety of features and can combine with many or few receptors • It is known that there isn’t one receptor for specific kinds of smells, our sense of smell works with ‘patter recognition’ http://en.wikipedia.org/wiki/Senses

  18. Human Senses • Taste or gustation: • This is a "chemical" sense • There FIVE main types of tastes that receptors (buds) in the tongue can distinguish: • Sweet • Salt • Sour • Bitter • Umami (SAVORIENESS) http://en.wikipedia.org/wiki/Senses

  19. Human Senses • Taste or gustation: • In 1908 a fifth receptor, for a sensation called umami (SAVORIENESS), was first theorized. In 200 its existence was confirmed. • The umami receptor detects the amino acid glutamate, a flavor commonly found in meat and in artificial flavorings such as monosodium glutamate (MSG) • Most of what we perceive (or describe as taste) is actually smell • E.g. “This ice-cream tastes like strawberry and banana”; it actually smells like banana and possibly tastes sweet and sour http://en.wikipedia.org/wiki/Senses

  20. Human Senses • Smell or olfaction • This combination of signals from different receptors makes up what we perceive as smell of substances or mixtures of substances (volatiles) • Volatiles are molecules of low boiling point at atmospheric pressure (1 atm or 760 mmg Hg) • Note: Taste is not the same as flavor! • Flavor includes the smell of a food as well as its taste • In the strawberry-banana ice-cream example the correct description would be ‘This cream has a strawberry-banana flavor’ http://en.wikipedia.org/wiki/Senses

  21. What is Sensory Analysis? • Identification of food product (s) properties • Scientific measurement of food product (s) properties • Analysis and interpretation of the identified and measured food product properties • AS THERE ARE PERCIVED THROUGH THE FIVE SENSES: - sight (e.g. color of a food product) - smell (e.g. presence of rancidity in a product) - taste (e.g. intensity of sweetness) - touch (e.g. firmness of a muscle food) - hearing (e.g. crunchiness of a potato chip)

  22. What Questions Sensory Analysis Answer? • Questions that deals with quality of food products under three main categories: • Discrimination • These questions have the objective of determining if differences exist between two or more products • Description • These questions have the objective of describing characteristics of a product and/or measuring any differences that are found between products • Preference or Hedonics • These questions have the objective of describing liking or acceptability of a product

  23. Why Use Sensory Analysis to Evaluate Food Products? • To evaluate quality (quality control) or improve quality • To provide input for decision making (product development) To determine the market value of a product • To determine shelf-life of a product • Ingredient substitution in product formulation To compare a product (s) with the competitor‘s product (s) • To determine storage conditions • To inspect products (regulatory agencies (e.g. fish spoilage)

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