| dc.description.abstract | SUMMARY The authors summarise those natural components of foodstuffs that may be harmful to consumers’ health either in their original quantity or after enrichment. They present the substances having nutritive effect that may exert a harmful effect on health due to inherited or acquired enzymopathy and they point out that the patients suffering from lactose intolerance, galactosaemia, phenylketonuria or celiac disease must keep a diet composed of lactose-, pheny-lalanine- and gliadin-free foods throughout their life. Furthermore, the authors discuss those substances (e.g. erucic acid, trans-fatty acids) that are harmful to the health of all consumers elevating the cholesterol level of the blood including the erucic acid occurring in large amounts in certain rapeseed oils, and trans-fatty acids forming during the hardening of oils through hydrogenation. Out of the non-nutritive toxic substances the authors pick out those toxic compounds that have the highest importance from the aspect of food safety, and that occur in certain raw materials as natural ingredients such as solanine, hydrogen cya-nide, methyl alcohol, morphine and its derivatives, as well as nitrate and nitrite. The authors discuss and summarise their undesirable and possible toxic effect such as (1) Solanidine originating from solanine has saponin-like effects: local tissue irritation, haemolysis and atropine-like nervous symptoms after absorp-tion. (2) Hydrogen cyanide released from cyanogenic glycosides upon enzymatic action inhibits the function of oxidative enzymes containing trivalent iron, such as cytochrome oxidase, resulted in inhibition of oxidative processes in the tis-sues and thus produces cytotoxic anoxia. (3) The toxic effect of methanol is due to this narcotising alcohol itself, and also to formic acid, which causes acidosis and retinal cell damage. (4) Morphine, codeine and thebaine (phenanthrene derivatives) are inhibitors of the central nervous system, while narcotine, narceine and papaverine (isoquinoline derivatives) are smooth muscle relaxants. (5) Nitrite, which is formed from nitrate due to microbial activity, induces methaemoglobin, has vasodilator effect, and can react with secondary and tertiary amines to form carcinogenic nitrosamines. | en_US |
