FST 1 Final Review
Terms
undefined, object
copy deck
- what are some advantages of dried foods other than preservation?
- Reconstitution is easy; less weight and volume of dried foods make it easier to store and cheaper to transport.
- What are the major advantages of using irradiation for preserving foods?
- it is a cold sterilization process, so no heat occurs during irradiation (if can be used on heat sensitive foods and used on frozen foods in its frozen state); foods sterilized by irradiation are essentially similar to canned foods and can be stored for prolonged periods of time and room temperature
- damage from intermittant thawing
- repeated freezing and thawing during storage is extremely detrimental to food quality. thawing can result in solute concentration effects while refreezing tends to cause small crystals to grow into large ones
- what kinds of factors affect the final flavor of wine?
- kinds of yeasts used, the temperature, the oxygen level, and the length of time that the juice is left in contact with the grape skin and seeds
- why is refrigeration a method of food preservation?
- this is the gentlest method with few effects on taste, texture, and nutritional value, and other quality of aspects of food. foods that would spoil in less than 24 hours can be stored up to 1 week at common refrigerator temperatures (5-78*C) and can be stored longer for up to 2 weeks at colder temperatures around 0*C
- why is the sugar and acid balance important for wines?
- the balance between sugar & acid is important in wine grapes; too little sugar or too little acid results in wine not fermenting cleanly or keeping well (flat tasting); too much acid results in sour wine or vinegary wine; too much sugar results in an undesirable sweetness
- what makes beer bitter?
- HOPS -- female flowers or cones of a Eurasian-American vine; it is picked off the plant, dried, and stored until needed// The resins from the hops makes beer bitter and their oils give off the aroma of beer
- concentration effects
- food must be solidly frozen to maintain highest quality. foods with unfrozen zones deteriorate because the liquid area concentrates salts, proteins, enzymes, which causes deteriorative changes
- what distinguishes the processing of living tissue foods from the processing of non-living tissue foods?
- quality in living tissue foods is usually best at harvest, while the quality for non-living tissue foods is determined by the quality of separation, assembly, and preservation operations.
- why does freezing food act as a method of preservation?
- in some foods, quality deterioration is virtually non-existent following frozen storage. no form of food preservation is as well suited to provide maximum convenience as freezing.
- the three basic freezing methods
- 1) air freezing-- cold air may be used with various degrees of velocity; 2) indirect contact freezing--indirect contact freezing includes those methods in which the food or the food package is in contact with a surface that in turn is cooled by a refrigerant, but the food, or food package does not contact the refrigerant directly; 3) immersion freezing-- immersion freezing involves direct contact of the food or package with the refrigerant either by submerging the food or spraying the cold liquid onto the food or package surface
- why would you use honey in breads and cakes?
- honey is more hygroscopic (due to the glucose and fructose) than table sugar, therefore it keeps breads and cakes more moist than sucrose
- how is brown sugar made?
- is it made by coating white sugar with a thin layer of molasses
- what are some quality changes that occur during dehydration? what is responsible for causing them?
- some food molecules become volatile and lost along with water (flavor components). changes in solute concentration can denature protein. change in shape of foods as they lose water and a number of chemical changes occur. foods can become discolored during drying by enzymatic browning reactions. heating results in quality losses, which includes browning, heating (scorched) flavor, denaturation of proteins, and other effects that result in the loss of solubility upon rehydration, textural changes, and loss of heat liable nutrients such as vitamins
- Secondary processing
- manufacturing; producing food ready for human consumption from raw materials which are not suitable for food (ex: flour+yeast+water= bread)
- why is beer less expensive than wine?
- the gain is much easier to grow and to harvest compared to grapes, and the grain can be stored either raw or malted for months before being fermented
- choice of final temperature
- the recommended temperature for long term frozen storage is -18*C (0*F) or lower. it is relatively easy and not excessively expensive to freeze food to even lower temperatures of -30*C. this latter temperature essentially completely inhibits most quality deterioration including enzymatic and chemical reactions which occur slowly at -18*C. the problem however is that it is generally not feasible to transport frozen foods below -18*C nor keep them in the home or the supermarket below -18*C. thus most food producers and retailers aim to prevent frozen foods from warming above -18*C.
- what are the four classes of food products one might find frozen?
- 1) perishable raw foods (meat, fish fruit, etc) -- requires little preparation other than washing to reduce microorganisms on the foods; 2) perishable heated or cooked foods (blanched veggies, TV dins, pies); 3) semiperishable foods -- breads, unheated dough products, butter; 4) nonperishable foods - nuts
- why do we distill alcoholic beverages?
- we distill alcoholic beverages because yeast cannot survive above 15% alcohol content ... distillation makes any alcoholic beverage a newer, stronger liquor.
- why is fermentation a method of food preservation?
- acids/alcohol produced as a byproduct inhibits other disease causing bacteria from growing
- What is the decimal reduction time (DRT or D value) ? What is the relationship between the D value and temperature?
- time to reduce the number of organisms to 1/10th of the original number when heated at constant temperature. The HIGHER the temperature, the SHORTER the DRT
- what food quality changes still occur during refrigerated storage?
- loss of firmness and crispness in fruits and vegetables, changes in color of red meat, oxidation of fats, softening of tissue and drippage from fish, staling of bread and cake, lumping and caking of granulated foods, changes in flavor, microbial spoilage.
- how does the away microwaves heat food differ from other cooking methods?
- Microwaves transfer heat via electromagnetic radiation in a lower energy band than the infrared region. unlike infrared waves that vibrate nearly all molecules, microwaves can only induce "polar" molecules to move. microwaves can penetrate foods to a depth of a few inches and heat food rapidly
- Why is it necessary to cool down the malt before fermentation?
- the malt is mashed into warm water, which re-activates the amylases and results in a sweet, brown liquid called "wort"
- Primary processing
- raw materials - deals with manufacturing foods and raw food materials for further food manufacturing by the "secondary" food processing industries
- Tertiary Processing
- preservation; transforming primary and secondary food materials into shelf stable, convenient foods
- Three different ways of transferring heat to food
- 1)conduction--heat source --> thermal energy --> food (heating food in a pan over a gas flame or electric burner); 2) radiation -- energy source --> heat energy --> food (broiling, microwave); 3) convection -- circulation of hot air and water --> heat (convention ovens -- heated air is circulated by a fan)
- what are some different types of air convection dryers?
- kiln driers, cabinet tray and pan driers, spray driers --> all possess insulated enclosure (air circulation within enclosure); heating air..
- The three classes of food processing operations
- 1) separation-- churning, filtration, skimming; 2) assembly--carbonating, stuffing, whipping; 3) preservation-- heating, boiling, pasteurizing
- other than the destruction of microorganisms, what are other reasons for heating food?
- to denature or inactivate enzymes that could reduce food quality (food spoilage). Most enzymes are irreversible inactivated at cooking temperatures
- what are the roles of the food processing industry?
- 1)manufacturing edible food items from mostly inedible agricultural products & 2) preserve the oversupply of agricultural products available at the time of harvest for consumption later in the year
- why is food dehydration a method of preservation?
- because of its effect on water activity; dehydration effectively lowers Aw to the point where no microorganisms, including those responsible for spoilage can grow. even molds cannot grow if the Aw is reduced to below .06. dried foods can reconstitute to its original composition at the point of final use with the use of water. most foods are predominantly water, so dehydration substantially reduces the volume and weight of foods and is important for the economics of transportation and prolonged storage.
- ice crystal damage
- ice crystals can damage cell walls and generally disrupt food texture. rapid freezing results in the formation of very small ice crystals that cause minimal damage, while very slow freeze generates large crystals that severely disrupt cellular foods, emulsions, foams, gels, ect
- how does aseptic canning differ from traditional canning methods
- the bulk food and container are sterilized separately, filled and sealed aspetically.
- what gives red wine its astringent taste and where does this compound come from?
- Tannin; it comes from a group of chemicals that are from woody substances in the skin and seeds of grapes
- why is sulfur dioxide (SO2) added to the grape must before adding yeast for fermentation?
- SO2 is added to suppress the growth of wild yeast and bacteria that turns sour grape juice into vinegar; SO2 also prevents oxidation of both flavor and pigment molecules; too much SO2 will give a bad odor!
- Describe the process of canning
- canning is a method of food preservation by heat. careful control of time and temperature is required ... 1) clean & prep -- remove all inedible parts, grade, and wash; 2) blanching -- inactivate enzymes to inhibit deterioration; 3) filling and exhausting-- fill until there is 1 cm left from the top of the can [for veggies/fruits, add liquid to very top), the cans are heated so that when a lid is sealed on and cooled, a partial vacuum will form; 4) sealing -- lids are placed on the cans, edges are rolled then flattened, forming an airtight seal; 5) sterilization -- determine amount of heat required for adequate sterilization [factors such as size of the can, contents of can, and pH of food play a part in how to sterilize); 6) cooling -- slow cooling to gradually reduce internal pressure in cans in order to minimize buckling...use chlorinated water to prevent contamination if temp. leakage should occur as the cans contract and cool.
- what are the two main sugars in honey?
- glucose, fructose
- What is "malting?"
- malting is the process in which dry barley kernels are first soaked in water to allow partial germination. The malt is dried to stop the enzyme activity and to kill the embryo ... the dried malt is then kilned (this causes Maillard browning and thus produces flavor and colors)
- What are the major disadvantages of using irradiation for preserving foods?
- the same processes that destroy microorganisms can also alter food components. Irradiation can affect the organoleptic quality of a food, depending on its chemical and physical structure. These changes can affect the maximum dosages that can be applied to certain foods, thus, it may not be possible to truly sterilize certain foods without significantly lowering their quality. however, low-dose irradiation pasteurization (radurization) has extended the normal storage life of marine products from a few days up to a few weeks with no detectable flavor change.
- what is tempering in chocolate production and why is it useful?
- "tempering" is the final step where chocolate is carefully and slowly cook. it is useful because ......................
- what might cause canned food to spoil?
- insufficient sterilization, leakage into a poorly made or improperly sealed container, corrosion of can
- rate of freezing
- the more rapid the rate of freezing the smaller the crystal ice formed, and the higher the quality of the frozen food. all modern methods of freezing and all freezing devices used in the food industry are designed for very rapid freezing rates.
- what is the process of freeze-drying based upon?
- removing water from previously frozen foods by the process of sublimation -- when water molecules are vaporized directly from the solid state. this occurs when food is 0*C or below an in a vacuum.
- what are the principle requirements for effective cold storage?
- 1) controlled low temperature; 2) proper air circulation (helps cold air move, but excess can dehydrate food); 3) proper humidity --too high of humidity will promote condensation of food surfaces and promote the growth of molds, while too low can cause foods to dry out.