Author: Glossary

  • Ptyalin

    Obsolete name for salivary amylase. An enzyme found in saliva that breaks down starch to simple sugars. An enzyme in saliva which cleanses the mouth and converts starch into sugar. Enzyme present in the mouth that starts the digestion of starches. The name of the enzyme contained in the saliva, by which starchy materials are…

  • Psychrophilic organisms

    Bacteria and fungi that tolerate low temperatures. Their preferred temperature range is 15-20°C, but they will grow at or below 0°C; the temperature must be reduced to about — 10°C before growth stops, but the organisms are not killed and will regrow when the temperature rises.  

  • P/S ratio

    The ratio between polyunsaturated and saturated fatty acids. In Western diets the ratio is about 0.6; it is suggested that increasing it to near 1.0 would reduce the risk of atherosclerosis and coronary heart disease.  

  • 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 by subtracting these values from the total (carbohydrate by difference). Also known as Weende analysis, after the Weende Experimental Station in Germany, which in 1865 outlined the methods of analysis to…

  • Provitamin

    A substance that is converted into a vitamin, such as 7-dehydrocholesterol, which is converted into vitamin D, or those carotenes that can be converted to vitamin A. A chemical compound which is converted to a vitamin during usual biochemical processes, e.g. the amino acid tryptophan, which is converted to niacin, and beta carotene, which is…

  • Protoporphyrin

    Haem molecule minus iron (i.e. the organic ring-structure without the central metal ion), the accumulation of which, in red cells, indicates either iron deficiency or other situations of impaired iron incorporation into haem, e.g. that caused by lead poisoning. Its quantitation in red blood cells can be used as a functional index of iron status.…

  • Proteome

    The protein complement of a cell, tissue or organism translated from its genomic DNA sequence. All of the proteins that can be synthesized from the DNA of an organism.  

  • Protein score

    A measure of protein quality based on chemical analysis.  

  • Protein retention efficiency (PRE)

    The net protein retention converted to a % scale by multiplying by 16, then becoming numerically the same as NPU.  

  • Protein quality

    A measure of the usefulness of a dietary protein for growth and maintenance of tissues, and, in animals, production of meat, eggs, wool, and milk. It is only important if the total intake of protein barely meets the requirement. The quality of individual proteins is unimportant in mixed diets, because of complementation between different proteins.…