Food chemistry
Properties of Food
Acidity (pH)
100% fruits and vegetables are acidulous (have a pH less than Septenary). E.g., an apple has the pH of in the area of Trinity.Three to Four.Cipher, based in kind & growing conditions. Leafy green vegetables have a pH of Quintuplet.Five to 6.Octad. Acidity assists to protect a food from either bacterium, virtually all of which take the neutral pH, especially the morbific ones. But, acidity doesn't prevent fungi like yeast, which is why fruit may ferment naturally.
Virtually all meat, dairy, and soy products have a neutral pH. Tofu has a pH of astir Seven.Deuce. Milk has a pH on the acidulent side of neutral, Sise.Four to 6.Eighter from decatur. Virtually all meats & fish have pH from Sixer.Three to 7.Quatern.
Super couple of nutrients come alkalic. One of a super couple of is conch, which has a pH from either Heptad.Five to 8.Quartet.
Water activity
Fluids activity is the proportional handiness of water system within the substance. Pure distilled the body of fluids has a water activity of exactly 1. the a lake activity of a food is critical within determining its shelf life. Nutrients by owning on line a water system activities like honey or molasses are stable for decades, in direct contrast high a stream activity nutrients like new fruit & milk spoil quickly. Highwater-activity substances trend lines additional microorganisms. Bacteria usually require a virtually all, & fungi the least. Watch fermentation.
a a water system system supply tends to migrate from either high water activity substances to great water activity substances. For instance, while honey is studied to humid air, a honey might soak up fluids from either a air. This migration is significant around numbers of nutrients — for instance, around sandwiches when water migrates from either the dampish filling to the bread, you make their way unappetising soggy bread.
Shelf life
Shelf life is the total of period the food may be potential to maintain its taste & safety. a shelf life of a food depends largely on the water supply activity, acidity, & the temperature its stored at. Dry acidulent nutrients stored at cool temperatures ordinarily have a hanker shelf life, when dampish neutral nutrients stored within warmly conditions spoil quickly. More factors could typically become influential, like a apply of preservatives and alcohol content, or anterior pasteurization.
Food processes
Browning
Browning occurs as vary within the food's color to become other dark through the production of black-colored melanins. There are deuce types of browning. Non-enzymatic browning, which does not necessitate a presence of enzymes, may be from either caramelization, by a Maillard reaction or by ascorbic-acid oxidation. Enzymatic browning is caused by enzymes such as polyphenyl oxidase.
Browning is responsible numerous of the tastes & colors of food. Chocolate, coffee, caramel, bread and roast beef are just two or three examples of nutrients for which browning is requisite. Browning can besides become deterimental. E.g., it makes apples and potatoes appear less appetising when it is cut.
Although browning is well achieved by the cook, these are the complex & incompletely understood chemical action. Apiece reaction has multiple pathways, a bit of of which create browning, when others vary flavor.
Fermentation
Fermentation is utilized about a earth as a way to preserve nutrients & have fresh flavors. Particularly, fermentation creates a taste umami, which is a unique symptom of the fermentation run.
A select few popular fermented nutrients include cheese, yogurt, bread, beer, wine, vinegar, pickles, soy sauce, and kimchi.
Pasteurization
Pasteurisation occurs as run which destroys the lot pathogens in a product, however doesn't kill bug that will deteriorate a quality of a product. Several pasteurised nutrients, like milk, come refrigerated to slow the incubation of micro-organism that kill product quality.