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Exam Review

8 Pages

Food Science
Course Code
FOOD 2010
David Stanley

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Exam Review 1. Types of packaging: Primary:flexible pouch, cans, glass containers, microwavable containers, edible films (sausage casing, wax on fresh fruit and veg) Secondary:cardboard box, Tertiary:corrugated box, shipping container, Quaternary: boxes assembled on wooden pallet together and wrapped with plastic wrap A primary package comes in direct contact with the food product (bag that cereal comes in); a secondary package (the cardboard box the bag is in with the photo and NFT) may also be involved. Tertiary (12 boxes of cereal in a case) and Quaternary packaging (12 cases on a pallet) usually refer to shipping and distribution packaging. 2. Substances formed during fermentation of fruits and vegetables: i. Ex. Cabbage: lactic acid – lowers pH and carbon dioxide - creates and maintains anaerobic conditions ii. Ex. Apples: carbon dioxide – provides carbonation, alcohol – contributes flavour 3. D-Value: used to determine the time and temp. combinations required to kill microorganism. Decimal Reduced Time (D-Value): time required for a bacterial population to pass through 1 log cycle, in which 90% of the organisms have been killed D121: time required to kill 90% of the bacterial population at 121degrees Celsius Non pathogenic Bacillus stearothermophilus used (great heat resistance) Clostridium botulinum (spores) most heat resistant pathogen 4. Major Steps in Cheese making: Cheese Processing Cheese is a concentrated dairy food that is allowed to cure or ripen in order to develop full flavor. Steps: -Curd Formation -Coagulating enzyme or acid precipitation of casein by lactic acid-producing bacteria -Cutting the curd into small pieces to remove residual whey -Heating the Curd to cause it contract -Draining, stretching, salting and processing the curd -Curing or Ripening Ripening allows cheese to develop desired characteristics of its own particular type. Penicillium roqueforti and P.glaucum are types of molds which are injected into the curd prior to ripening. 5. What determines Meat colour? Why is fresh red meat bright red, but meat that is not fresh brown? - To understand we must look at the muscle pigment molecule called myoglobin Myoglobin: -Is a single polypeptide -A globular protein containing the globin protein and a prosthetic group called heme. -Myoglobin has the ability to bind oxygen because of the globin polypeptide tertiary structure and because of the heme which is an iron porphyin ring complex -In nitrate cured means, myoglobin reacts with nitric oxide (NO) to produce nitric oxide myoglobin (aka nitrosylmyoglobin) which is bright pink red. -Brown colour development can occur during storage of cured meats, since oxygen and light exposure cause ferrous iron to oxidize to ferric iron 6. Defects caused by improper aging of meat: Rigor mortis- is a transient postmortem physical and biochemical event that takes place in animal muscle tissue. It causes a loss of extensibility of the tissue, which makes meat very tough. Myosin stays locked onto actin. Cold Shortening- is a quality problem that results from the rapid chilling of carcasses immediately after slaughter, before the glycogen in the muscle has been converted into lactic acid. It causes meat to be as much as five times tougher than normal. High voltage current (electrical stimulation) to postmortem carcasses minimizes this defect. Thaw rigor- When meat is frozen before it enters rigor mortis. When thaw rigor meat is thawed, the leftover glycogen allows for muscle contraction and the meat becomes extremely tough. PSE (Pale soft and exudative)- meat is the result of a rapid postmortem pH decline in pork while the muscle temperature is too high. Affects muscle proteins reducing their ability to hold water. Yields undesirable colour changes the production of slime layer and fatting out. 7. Maillard Browning: Maillard Reaction: A type of browning reaction, like the caramelization of sugars that occurs between naturally occurring reducing sugars and amino acids, amines, small peptides, and protein. EG: Bread -Aroma of bread is lost upon cooling and storage -This is due to volatility of aroma molecules -Bread flavour originates mainly from baking and fermentation -Crust formation and browning are main contributors to flavour -During bread baking the Maillard Reaction generates dicarbonyl compounds (HOC-COH). These react with amino acids like glycine (H N-CH -COOH) Through a series of steps known as Streker Degradation to 2 2 produce pyrazine. -Pyrazines are similar to benzene rings except two carbons are replaced with Nitrogen. -Pyrazines contribute to flavour and aroma 8. Anthocyanins: Water soluble flavonoid compounds Range in colour from deep purple to orange – red Anthocyanin pigment colour is pH sensitive: Red = strong acid Colourless @ pH 4 Blue = neutral pH Ex. Red- purple pigment of grapes, pigments in eggplant, red cabbage, radish and red potato Anatomically, anthocyanins are found in the cell vacuole, mostly in flowers and fruits but also in leaves, stems, and roots. In these parts they are found predominantly in outer cell layers such as the epidermis and peripheral mesophyll cells. Plants rich in anthocyanins are vaccinium species, such as blueberry, cranberry and bilberry, rubus berries including black raspberry, red raspberry and blackberry, blackcurrant, cherry, eggplant peel, black rice, Concord grape and muscadine grape, red cabbage and violet petals. Anthocyanins are less abundant in banana, asparagus, pea, fennel, pear and potato, and may be totally absent in certain cultivars of green gooseberries. 9. Hurdle technology- a hurdle is a stress placed on a microorganism that it must overcome in order to survive, grow and reproduce in food. Hurdles are equivalent to the factors affecting microbial growth: water activity, pH, temperature, pressure and chemical antimicrobials. Hurdle technology creates a combination of suboptimal growth conditions in which each hurdle factor alone is insufficient to prevent the growth of spoilage and pathogenic organisms but hurdles used in combination provide effective control. 10. Encapsulation Examples: Encapsulation: Is a technique applied to flavours to accomplish convenience, stability, and time release. Ex: Encapsulated oleoresins and oils are dry powders to which thin, polymeric coatings have been applied. Coatings are composed of maltodextrin, modified starches, or vegetable gums. They offer a temporary barrier to heat, low pH, oxygen, and moisture, making flavour compounds more stable during storage Encapsulation techniques protect flavour from a variety of destructive conditions: Thermal Processing Conditions: Baking, deep frying, extrusion, retorting, Storage Conditions: Low temp, high temp, oxidation, pH, Consumer Conditions: Cooking, freezing, refrigeration, reheating, Off flavours, Hydrolytic Rancidity, Oxidative Rancidity, Warmed Over Flavour 11. Blanching- is a type of treatment applied to fruits and vegetables that is specifically intended to inactivate natural food enzymes. It is a low temperature heating process applied in order to not harm the quality and texture of the food. 12. Advantages of Retorting: In a retort canner heat energy is transferred from the heating source to the food inside each container of food by conduction and convention. Retort processing is the procedure that is used to heat sealed cans in order to destroy bacteria and spores. It uses a chamber with steam valve jets that allow steam to enter the chamber for precise temperature control. 13. Ohmic Heating – resistance heating is an efficient alternative to traditional methods in which a food product is subjected to an alternating current within a conducting ionic solution 14. Radioisotopes used for irradiating food: Irradiation – is a pasteurization method accomplished by exposing meat to low and medium doses of radiation generated by electron accelerators or by exposure to gamma sources. This causes lower microbial contamination. Food irradiation involves the use of either high speed electrons from an electron beam, electron accelerator or high-energy gamma ionizing energy such as that given off by radioisotopes Co-60 (radioactive cobalt) or Cs-137 (radioactive cesium). E-beam technology uses high-energy electrons to destroy harmful microorganisms within seconds by penetrating products in their final shipping packaging. Unit of absorbed dose in food is given in kilogray (kGy) = 1000 Grays 1 Gray = absorption of 1 joule of energy by 1 kg of food. One dose of irradiation is divided into three levels: 1) radicidation – less than 1kGy (low dose) 2) radurization- dose of 1-10 kGy (medium dose) 3) radapperization- dose of 20 to 30 kGy (high dose) The intramolecular radiation damage can break bonds connecting base pairs, impairing cellular biochemistry and metabolism  cell death. Irradiation also exerts indirect effects on microorganisms that destroy them. Free radical refers to an atom or molecule having an unpaired electron. They produce oxidizing agents which can damage bacterial cell components. Irradiated foods are safe from pathogens. 15. Oil refining: Compounds removed through oil refining which would otherwise contribute undesirable flavours, odours or product instability are; aldehydes, free fatty acids, gums, lecithin, ketones and soaps. Refers to the removal of impurities from the extracted fat or oil. When food lipid matter is obtained via pressing and rendering, it is referred to as an edible Crude Oil. 16. Risk of eating shellfish: Marine toxins • Caused by ingestion of shellfish and finfish containing toxins • Toxins produced by living creatures that the fish eat called dinoflagellates that carry out metabolism through photosynthetic reations • They cluster ont he surface of tropical seaweed which are consumed by fish PARALYTIC SHELLFISH POISONING, NEUROTOXIC SHELLFISH POISONING, DIARRHETIC SHELLFISH POISONING, AMNESIC SHELLFISH POISONING 17. Heat energy applied to foods causes them to increase in molecular motion and temperature. At different phases, solids, liquids and gases have different ranges of motion. Absolute zero (zero degrees Kelvin) is the temperature at which all motion stops. Transfer of heat energy to foods comes in 3 methods: conduction, convection, radiation. • Conductive: accomplished at a molecular level where vibrations are passed from molecule to molecule (there is a conductive substance the heat is transferred from) as heat moves through a material. • Convection: heat is exchanged between liquid or gases and solids; there is movement from hot to cold. • Radiation: direct transfer of energy from one surface to another without intervening medium and is dependant on emission and absorption of the surfaces. 18. Microwave Energy: • Introduced in the 1970s • Effective in heating foods because foods contain water. The dipolar molecule of water is the electrically active substance allowing microwaves to heat foods. • Microwaves are part of the electromagnetic spectrum, with a characteristic of wavelength and frequency. • Microwaves create a fluctuating electrical field inside a microwave oven that changes direction 2.45 billion times a second. (the
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