Food science
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Food science is a discipline concerned with all aspects of food - beginning after harvesting, and ending with consumption by the consumer. It is considered one of the agricultural sciences, and it is a field which is entirely distinct from the field of nutrition. In the U.S., food science is typically studied at land-grant universities.
Examples of the activities of food scientists include the development of new food products, design of processes to produce these foods, choice of packaging materials, shelf-life studies, sensory evaluation of the product with potential consumers, microbiological and chemical testing. Food scientists in universities may study more fundamental phenomena that are directly linked to the production of a particular food product.
Food scientists are generally not directly involved with the creation of genetically modified (bio-engineered) foods.
Some of the subdisciplines of food science:
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Properties of Food
Acidity (pH)
Nearly all fruits and vegetables are acidic (have a pH less than 7). For example, an apple has a pH of around 3.3 to 4.0, depending on variety and growing conditions. Leafy green vegetables have a pH of 5.5 to 6.8. Acidity helps to protect the food from bacteria, most of which require a neutral pH, especially the pathogenic ones. However, acidity does not stop fungi like yeast, which is why fruit will ferment naturally.
Most meat, dairy, and soy products have a neutral pH. Tofu has a pH of about 7.2. Milk has a pH on the acidic side of neutral, 6.4 to 6.8. Most meats and fish have pH from 6.3 to 7.4.
Very few foods are alkaline. One of the very few is conch, which has a pH from 7.5 to 8.4.
Water activity
- See Water activity
Water activity is the relative availability of water in a substance. Pure distilled water has a water activity of exactly one. The water activity of a food is critical in determining its shelf life. Foods with low water activities such as honey or molasses are stable for decades, in contrast high water activity foods such as fresh fruit and milk spoil quickly. Higher water-activity substances support more microorganisms. Bacteria usually require the most, and fungi the least. See fermentation.
Water tends to migrate from high water activity substances to low water activity substances. For example, when honey is exposed to humid air, the honey will absorb water from the air. This migration is important in many foods — for example, in sandwiches when water migrates from a moist filling to the bread, you get unappetizing soggy bread.
Shelf life
- See Shelf life
Shelf life is the amount of time a food can be expected to maintain its taste and safety. The shelf life of a food depends largely on the water activity, acidity, and the temperature its stored at. Dry acidic foods stored at cool temperatures usually have a long shelf life, while moist neutral foods stored in warm conditions spoil rapidly. Other factors can often be influential, such as the use of preservatives and alcohol content, or prior pasteurization.
Food processes
Browning
Browning is a change in a food's color to be more brown through the production of brown-colored melanins. There are two types of browning. Non-enzymatic browning, which does not require the presence of enzymes, can be caused by caramelization, by a Maillard reaction or by ascorbic-acid oxidation. Enzymatic browning is caused by enzymes such as polyphenyl oxidase.
Browning is responsible for many of the tastes and colors of food. Chocolate, coffee, caramel, bread and roast beef are just a few examples of foods for which browning is essential. Browning can also be deterimental. For example, it makes apples and potatoes appear less appetizing after they are cut.
Although browning is easily achieved by a cook, it is a complex and incompletely understood chemical process. Each reaction has multiple pathways, some of which produce browning, while others alter flavor.
Fermentation
- See Fermentation
Fermentation is used around the globe as a way to preserve foods and develop new flavors. In particular, fermentation creates the taste umami, which is a unique result of the fermentation process. Some popular fermented foods include cheese, yogurt, bread, beer, wine, vinegar, pickles, soy sauce, and kimchi.
Pasteurization
- See Pasteurization
Pasteurization is a process which destroys all pathogens within the product, but does not destroy microbes that may deteriorate the quality of a product. Many pasteurized foods, such as milk, are refrigerated to slow the growth of microorganisms that destroy product quality.