Shreela’s review
Food production principles:
Dispersion systems-mixture of various substances in solid, liquid, or gas state
Gas in solid-sponge cake
Liquid in liquid-mayonnaise
Solid in liquid-proteins in milk
True solution-small particles such as sugar or salt dissolved in a solution, may be
ionic or molecular
Colloidal dispersion
-large particles such as proteins or cooked starch dissolved in
a solution
-often unstable to such factors as heating, freezing, or pH change
Gel-a two-phase system, but it is an elastic solid with a liquid dispersed phase in a
solid continuous phase
Suspension-particles too large to form a colloidal dispersion
-particles in a suspension separate out over time, whereas no such separation is
observed with colloidal dispersions
Degree of dispersion-varies through heating or beating solution
Interface-line that forms btw two immiscible liquids (oil and water)
Function of acid-in vegetables, angel food cake
Acid in Vegetables means:
· It is important to process at a temperature >212 F to destroy botulism (can use pressure cooker)
· It can still be pickled with a vinegar acid
· A loss of green color in green vegetables during extensive cooking or canning; the chemical rxn due to high heat causes the disrupted molecule to become Pheophytin turning the vegetable olive green or brown
Acid in Angel Food Cake means:
· Product contains cream of tartar
· It maintains white color by preventing a browning rxn
· A larger volume product by stabilizing egg white foam
· A tender crumb product is produced
Note: without the tartar, the product would be yellow, small, and tough
Function of enzymes
· Function as catalysts to facilitate chemical reactions
· Exist mainly as proteins, which are effected by temperature and pH
· Contribute to the role of ripening in fruit by converting starch to sugar, causing browning of cut surfaces
· Inhibited by addition of an acid, and/or heat
Browning reactions
· Maillard rxn-nonenzymatic rxn that occurs as reduced sugars and amino acids combine; can be increased through an increase in pH and temp, and a decrease in water content of product. Example: browning of bread
· Enzymatic rxn-example: cutting surface of fruit
· Caramelization-sugars caramelize on heating, giving a brown color.
o Caused by the decomposition of the sugars and occurs at extremely high temperatures.
o Different from Maillard b/c doesn’t involve proteins
Heat transfer-conduction, convection, radiation
· Conduction-movement of heat from one particle to another (meat kept warm on dish sitting on heated pellet)
Good conductors-copper, black cast iron, aluminum
Poor conductors-glass and stainless steal
· Convection-movement of heat using air currents ( meat cooked in convection oven)
· Radiation-infrared waves coming from glowing heat (meat cooked by toasting, broiling, microwaving)
Note: disadvantage of using microwave cooking is uneven heat distribution, lack of browning in foods cooked for a short time, not good for simmering or stewing
Preservation and packaging methods
Food spoilage-molds, yeasts, bacteria, enzymes
*Mold and yeast are fungi that may be responsible for spoilage in the food supply
Mold
-the unwanted blue, green, white, and black fuzzy growth on food and is only considered acceptable in penicillin and some cheeses such as blue or black cheese.
-Molds do not require as much moisture for growth as yeasts and bacteria do
-Do not require temlperatures much above average room temp
-Molds can be used in the production of citric acid, ex. beet molasses
Yeasts
-larger than molds and reproduce by creating buds
-spread through the air and can be both harmful and useful in foods
-Used in making of bread
-Yeast produces carbon dioxide which when heated expands the dough and makes the final product light and porous
-The source of carbon dioxide is sugar
-Fermentation leavens the dough and renders the gluten of the flour more elastic when combined with a liquid
-During the fermentation process, yeast cells convert fermentable sugars into ethanol and CO2
-Alcoholic beverages depend on the fermentation brought on by certain strains of yeast for their flavor and color
Bacteria
-Bacteria may cause foodborne illnesses such as infection, intoxication, or toxin-mediated infection
-Foodborne infection-results from ingesting living, pathogenic bacteria such as Salmonella, Listeria, or Shigella
-Foodborne intoxication-may result if a preformed toxin(poison) such as that produced by Staphylococcus aureus, Clostridium botulinum, and Bacillus cereus, is present in the food
-Toxin-mediated infection-is caused by ingestion of living, infection-causing bacteria such as Clostridium perfringens and E. coli which also produce a toxin in the intestine
-In order to grow, bacteria need protein or sufficient nutrients, moisture-water activity above 0.85, a pH above 4.5, oxygen if aerobic, and a general temperature 40-140 F-the temperature danger zone
Enzymes
-Biological catalysts that accelerate the rate of a chemical rxn, often to as much as a billion times faster
-Blanching, or briefly immersing the food into boiling water, denatures the enzymes so that they cease to be functional or active
-Meat can be made tender by the use of proteolytic enzymes
-Commerically the most important are proteases from the green fruit of the papaya plant: papain, chymopapain, and a peptidase
-They attack and degrade proteins in the myofibrils and also act on connective tissue when heat has disrupted the coiled structure
-Proteolytic enzymes prevent gelation b/c they denature proteins
Method of food preservation
Chemical preservation
-The purpose of chemical additives: to retard food spoilage caused by microoganisms and prolong shelf life beyond that of refrigeration, drying, freezing, fermenting, and curing
-Chemical preservatives interfere with the cell membranes of microorganisms, their enzyme activity, or their genetic mechanism
-Chemical preservatives are usually added after the food has been processed and before it is packaged
-subject to FDA approval
-One foodborne illness that remains in question is that which results from the use of too much monosodium glutamate (MSG), a food additive that serves as a flavor enhancer
Acids
-denatures bacterial proteins, preserving food, although not always sufficient to ensure sterility.
-Acid may be naturally present in foods such as citrus fruits and tomatoes
-The combination of acid and the application of heat offers more effective preservation
Sugar and salt
-Heavy syrups or brines compete with bacteria for water
-By osmosis, the high percentage of water moves out of bacterial cells to equal the lower level of water in the surrounding medium
-Other microorganisms, such as the fungi, yeast, and mold, are capable of growing in a high sugar or salt environment
-Early U.S. settlers preserved meats using salt and sugar (I’m sure you all care)
Service systems: