Benders'dictionary of nutrition and food technology

179evaporation, flash A short, rapid application of heat so that asmall volume (about 1% of the total) is quickly distilled off, carryingwith it the greater part of the volatile components.The flashdistillate is collected separately from the later distillate and isadded back to the concentrate to restore the flavour; applied tothe concentration of products such as fruit juices.evening primrose Oenothera biennis.The oil from the seeds is arich source of γ-linolenic acid, which may account for 8% oftotal fatty acids. Used as a dietary supplement and claimed tohave beneficial effects in a number of conditions, with some evidenceof efficacy.exchange list List of portions of foods in which energy yield, fat,carbohydrate and/or protein content are equivalent, so simplifyingmeal and diet planning for people with special needs.exclusion diet A limited diet excluding foods known possibly tocause food intolerance (see adverse reactions to foods), towhich foods are added in turn to test for intolerance.exergonic Chemical reactions that proceed with the output ofenergy, usually as heat (then sometimes known as exothermicreactions) or light. The reactions involved in the oxidation offoodstuffs are generally exergonic.exhausting Removal of air from a container before processing.exon A region of DNA within a gene that contains informationcoding for the protein that is retained during the posttranscriptionalmodification of mRNA.See also intron.exopeptidases Proteolytic enzymes that hydrolyse the peptidebonds of the terminal amino acids of proteins or peptides, asopposed to endopeptidases, which cleave at sites in the middleof a peptide chain. There are two groups: aminopeptidases (EC3.4.11.x) which remove the amino acid at the amino terminal ofthe protein, and carboxypeptidases (EC 3.4.16.x and 3.4.17.x),which remove the amino acid at the carboxyl terminal.exophthalmus Protrusion of the eyeballs from the sockets, commonlyassociated with hyperthyroid goitre.exotoxins Toxic substances produced by bacteria, which diffuseout of the cells and stimulate the production of antibodies whichspecifically neutralise them (antitoxins).They are generally heatlabileand inactivated in about 1 h at 60 °C. Exotoxins includethose produced by the organisms responsible for botulism,tetanus and diphtheria.See also endotoxins; tx numbers.expansion rings In relation to cans, the concentric rings stampedinto the ends of the can to allow bulging during heat processingwithout straining the seams.