Benders'dictionary of nutrition and food technology

395provitamin A substance that is converted into a vitamin, such as7-dehydrocholesterol, which is converted into vitamin d, or thosecarotenes that can be converted to vitamin a.provolone Smoked drawn curd cheese, originally made frombuffalo milk, now mainly cow milk.proximate analysis Analysis of foods and feedingstuffs for nitrogen(for protein), ether extract (for fat), crude fibre and ash(mineral salts) together with soluble carbohydrate calculated bysubtracting these values from the total (see carbohydrate by difference).Also known as Weende analysis, after the WeendeExperimental Station in Germany, which in 1865 outlined themethods of analysis to be used.Prozac See fluoxetine.prunin See naringin.Prunus Genus of plants including plums, peaches, nectarines,cherries and almonds.Pruteen TM Microbial protein produced by growing Methylophilusmethylotrophus, on methanol; 70% protein in dry weight.pseudoalkaloids Pharmacologically active compounds in plants,unlike alkaloids and protoalkaloids, not derived from aminoacids; two major groups: (i) steroid and terpene derivatives and(ii) purines (e.g. caffeine).pseudoglobulin Water-soluble globulin which is not precipitatedfrom salt solutions by dialysis against distilled water.Pseudoglobulins occur in blood plasma, in animal tissues, and inmilk.See also euglobulin.pseudokeratins See keratin.pseudoplastic Material whose viscosity decreases with increasingshear rate.See also dilatant; rheopectic; thixotropic.PSL Practical storage life.PSP See paralytic shellfish poisoning.P:S ratio The ratio between polyunsaturated and saturated fattyacids. In western diets the ratio is about 0.6; it is suggested thatincreasing to near 1.0 will reduce the risk of atherosclerosis andcoronary heart disease.PSW Pulsed shock waves, a technology proposed for preservationof foods by inactivation of enzymes without heating, throughgenerating shock waves by powerful electric discharge in liquids.psychrometer See hygrometer.psychrometry Study of the interrelationships of temperature andhumidity relevant to drying with hot air.psychrophiles (psychrophilic organisms) Bacteria and fungi thattolerate low temperatures. Their preferred temperature range is