Benders'dictionary of nutrition and food technology

374rate. Calculated from the physical activity ratio for each activity,multiplied by the time spent in that activity. A desirable PALfor health is considered to be 1.7; the average in UK is 1.4.physical activity ratio (PAR) energy cost of physical activityexpressed as a ratio of basal metabolic rate.physin Name given to a growth factor in liver, later identified asvitamin b 12 .physiological saline A solution of sodium chloride that is isotonicwith blood plasma, 0.15 mol/L (9 g/L).phytase Enzyme (inositol hexahydrate phosphohydrolase, EC3.1.3.26) that hydrolyses phytate to inositol mono- to tetrakisphosphates(tetraphosphates), which do not chelate minerals,and free phosphate. Occurs in cereal grains, where it is activatedby soaking or during germination and malting. Added to poultryfeed to increase availability of phosphate; main commercialsource is Aspergillus spp., but also expressed in genetically modifiedrapeseed, tobacco and tomato seeds.phytic acid (phytate) inositol hexaphosphate, present in cereals,particularly in the bran, dried legumes and some nuts as bothwater-soluble salts (sodium and potassium) and insoluble salts ofcalcium and magnesium. Magnesium calcium phytate is phytin.Can bind calcium, iron and zinc to form insoluble complexes; itis not clear how far phytate reduces the availability of these mineralsin the diet, especially since there is phytase in yeast andlegumes (and possibly in the human gut) which may liberatethese minerals.phytin Magnesium calcium phytic acid, approximately 12%calcium, 1.5% magnesium and 22% phosphorus.phytoagglutinins See lectins.phytoalexins Compounds produced by plants under conditionsof stress or in response to mechanical or fungal damage whichmay be toxic, or induce adverse reactions, when the plants areconsumed.phytochromes Also known as florigens. Photosensitive polypeptideswith a tetrapyrrole prosthetic group, responsible forday-length sensitivity in plants, and possibly also enhancedgermination of seeds that have been vernalised (chilled to 4 °C).The protein undergoes a conformational change on exposure tored light (660 nm) and the reverse change on exposure toinfrared (735 nm).phytoestrogens Polyphenols (see flavonoids) found in a varietyof plant foods that have oestrogen activity.phytohaemagglutinins See lectins.phytoncides See pacificarins.phytoplankton See plankton.