Benders'dictionary of nutrition and food technology

412rheopectic (rheopexic) A fluid whose structure builds up withcontinued shear stress, so that viscosity increases, as is the casewith whipping cream.See also dilatant; pseudoplastic; thixotropic.rhizome Botanical term for swollen stem that produces roots andleafy shoots.rhizopterin Obsolete name for folic acid.rhodopsin The pigment in the cone cells of the retina of the eye,also known as visual purple, consisting of the protein opsin andretinaldehyde, which is responsible for the visual process. In rodcells of the retina the equivalent protein is iodopsin.See also vitamin a; dark adaptation; vision.Rhodotorula Yeasts that may cause red, pink or yellow discolorationin foods.rhubarb Leaf-stalks of the perennial plant, Rheum rhaponticum.Has a high content of oxalic acid (the leaves contain even more,and are toxic).Composition/100 g: (edible portion 75%) water 94g, 88 kJ(21 kcal), protein 0.9 g, fat 0.2 g, carbohydrate 4.5 g (1.1 g sugars),fibre 1.8g, ash 0.8g, Ca 86mg, Fe 0.2mg, Mg 12mg, P 14mg, K288mg, Na 4mg, Zn 0.1mg, Mn 0.2mg, Se 1.1µg, vitamin A 5µgRE (231µg carotenoids), E 0.4 mg, K 41 mg, B 1 0.02 mg, B 20.03 mg, niacin 0.3 mg, B 6 0.02 mg, folate 7 µg, pantothenate0.1 mg, C 8 mg. A 140 g serving is a source of Ca, Mn, vitaminC.RIA See radioimmunoassay.Ribena TM A blackcurrant juice cordial.riboflavin See vitamin b 2 .ribonucleic acid (RNA) See nucleic acids.ribose A pentose (five-carbon) sugar that occurs as an intermediatein the metabolism of glucose; especially important in thenucleic acids and various coenzymes: occurs widely in foods.ribosomes Intracellular organelles consisting of proteins andRNA that catalyse the synthesis of proteins (translation). Ribosomesbind to, and travel along, mRNA, binding aminoacyltRNA to each codon in turn, and catalysing the synthesis ofpeptide bonds. A series of ribosomes translating the same strandof mRNA is known as a polysome. Proteins destined for exportfrom the cell are synthesised by ribosomes attached to the roughendoplasmic reticulum of the cell.Ribotide TM A mixture of the purine derivatives, disodium inosinateand guanylate, used as a flavour enhancer for savourydishes.ribotyping Method for identification of bacteria using DNAprobes to identify their ribosomal RNA.