Moulds able to grow on very dry foods are termed
Answer: C
Xerophilic moulds grow at moisture levels far below those any bacterium can tolerate, which is why dried fruit, grain and spices spoil by moulding rather than by bacterial action. They set the practical limit for how dry a food must be kept.
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Honey resists most microbial spoilage because of its
Answer: D
Correct answer: very low available water and high sugar content
Honey is roughly eighty per cent sugar and holds only a little water, and that water is bound so tightly by the sugar that the water activity falls to around 0.6 - below what any bacterium can grow at. Its acidity and its glucose oxidase, which generates hydrogen peroxide, reinforce the effect, but the low water activity is the principal barrier.
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Honey may contain the spores of
Answer: A
Honey is the one dietary reservoir of Clostridium botulinum spores definitively linked to infant botulism, by both laboratory and epidemiological evidence. The spores survive the low water activity that prevents anything growing.
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Honey should not be given to infants below the age of
Answer: B
Correct answer: one year
Honey can carry spores of Clostridium botulinum, and although the spores are harmless to older children and adults, an infant’s gut flora is not yet established enough to suppress them. The spores can germinate there and produce toxin in the intestine, causing infant botulism. The exclusion applies for the first year of life.
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Older children and adults are unharmed by the spores in honey because
Answer: C
A mature intestinal microbiota outcompetes Clostridium botulinum so that the spores pass through without colonising. The infant gut has not yet developed that community, which is the whole basis of the age restriction.
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Infant botulism results from
Answer: D
Unlike foodborne botulism, where toxin already present in the food is eaten, here the organism colonises the intestine and makes toxin in place. That difference explains why the food itself may contain no toxin at all.
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Salmonella is a recognised hazard in chocolate because it
Answer: A
The organism cannot grow in chocolate but persists in it for months, and the fat coating protects it from stomach acid, so a very small number of cells can cause illness. Several large outbreaks have been traced to chocolate for exactly this reason.
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Jams and preserves owe their keeping quality chiefly to
Answer: B
Correct answer: a high sugar concentration binding the water
Jam holds around sixty-five per cent sugar, which binds the water so that the water activity falls below what most spoilage organisms can tolerate. The high acidity of the fruit and the heat of boiling assist, but it is the sugar that provides the standing barrier - which is why a jam made with reduced sugar needs refrigeration.
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Aflatoxins are produced by
Answer: C
These two Aspergillus species are the aflatoxin producers, growing on crops in the field and in poorly dried storage. The Penicillium species named are used in cheese making, and the Fusarium species produce a quite different group of toxins.
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Aflatoxin contamination is a particular problem in
Answer: D
Cereals such as maize, sorghum, wheat and rice, together with oilseeds, spices and tree nuts, are the crops frequently affected. Groundnuts stored warm and damp are the classic case, and the toxin can carry into milk if contaminated feed is given to cattle.
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