R.J. Neale

Characterisation of starches from West African yams

Starches from four varieties of West African yams were extracted and characterised. The physicochemical properties investigated (granule size and morphology, amylose content, crystal form, gelatinisation and pasting behaviour) depended strongly on the yam variety. The starch granules extracted from water yam (Dioscorea alata), white yam (D rotundata) and yellow yam (D cayensis) varieties showed mononodal particle size distributions centred between 31 and 35 µm, while the bitter yam (D dumetorum) exhibited a binodal size distribution of starch granules centred at 4.5 and 9 µm. Light microscopy confirmed the variation in starch granule size and shape with yam variety. The X-ray diffractogram of yellow yam was of the B type, while bitter yam showed an A pattern. The starches extracted from the white and water yams were of the intermediate C-type patterns. The temperatures of onset of gelatinisation were derived from DSC and RVA measurements; values of 69.4 and 75.0 °C for the yellow yam, 71.5 and 78.2 °C for the white yam, 76.5 and 79.8 °C for the water yam and 78.1 and 83.1 °C for the bitter yam were obtained. © 1999 Society of Chemical Industry

Effect of the Extent of Conversion and Retrogradation on the Digestibility of Potato Starch

The effect of starch conversion on the susceptibility of potato granules to α-amylase was studied by direct sampling at different pasting times corresponding to different points on the RVA profile of a 6.4% (w/w) suspension of starch in distilled water. Native granules showed high resistance to α-amylase with 8.6 ± 0.4% digestibility for a 6 h incubation period with the enzyme. When the suspension was heated to 60 °C, the digestibility increased to 53.5 ± 0.7% although, at this temperature, there was still no noticeable increase in the measured viscosity (≤ 0.040 Pa.s). The material sampled after a pasting time corresponding to the RVA peak viscosity showed a digestibility of 88.4 ± 0.5%. This suggested, owing to the expected retrogradation of amylose on cooling, the quasi-total susceptibility of amylopectin to enzymatic digestion at this pasting stage. The effect of ions on the swelling of potato starch was used to assess whether the decrease of the swelling of the granules in the presence of NaCl was paralleled by an increase in resistance to α-amylase. A small (∼ 6.1%) but significant decrease in the digestibility of pasted starch was observed in the presence of salt. Finally, the effect of the retrogradation of the amylopectin fraction on its digestibility was assessed in extruded potato starch ribbons containing 35% (w/w) water and stored at different temperatures. After 14 days of storage, the digestibility decreased from 77.0 ± 0.9% in the freshly extruded samples to between 28.0 ± 1.7% and 42.1 ± 0.3%, depending on the storage temperature. This suggested a measurable difference in the α-amylase susceptibility between the A and B polymorphs of retrograded amylopectin.

Children's food purchase requests.

A survey of 507 parents of 7- to 11-year old children was conducted within the Central television district of the U.K. The aim was to determine what products children had a propensity to consume by using their purchase requests to parents as an indicator. In addition, other questions concerning eating patterns, socio-economic status and lifestyle were asked in an effort to identify influences on purchase requests.

Children′s Food Preferences: Television Advertising vs Nutritional Advice

Reports a survey of 507 parents of 7 to 11‐year‐old children in the Central Television district of the UK to ascertain what food products children requested and the effects of television advertising on children′s food preferences. The questionnaire found that 45 per cent of products requested had an extrinsic sugar content and 39 per cent of requests were for advertised foods. In addition a wide range of products were requested reflecting sophisticated tastes and, sometimes, healthy eating concern. Discusses the contradictory nature of messages about food that children receive and suggests that healthy eating campaigns should use specific food items as examples and advertisements should convey non‐misleading nutritional information.

Dietary Awareness of Primary School Children

The dietary awareness of primary school children towards selected food items and components including bread, potatoes, dairy products, fat, fish, meat, fresh fruit, salt, sugar and sweets was evaluated using an interview technique. The children were asked whether they ought to eat more, the same or less of each food and the results are presented for the sample of younger and older children. The results indicate that these selected food items can be broken down into three main areas. First there are those where the majority of children thought we ought to increase consumption; bread, potatoes, dairy products, fish, meat and fresh fruit. Second there is a group of food components including salt, fat and sugar in which there is closer similarity in those advocating more or less consumption. Third there are the food products such as sweets where there are significant differences between age groups, and changes in attitude occur in a limited age span. A discussion of the implications of this work for nutrition...

Vitamin C status and other nutritional indices in patients with stroke and other acute illnesses: a case-control study

Sixty-three patients with acute thrombotic stroke were compared with 47 age and sex-matched patients admitted concurrently with acute ischaemic cardiac pain and a further 44 with acute noncardiovascular illnesses. Overall the stroke patients scored highest on a questionnaire designed to estimate mean daily intake of vitamin C before hospital admission. There were problems with this retrospective dietary assessment, however, and the diet scores of the 27 stroke patients able to answer the questionnaire themselves fell between those of the other two groups. There were no significant differences between the three patient groups in plasma ascorbic acid or uric acid levels, but plasma magnesium and albumin levels were higher in the stroke patients. These findings were similar for patients aged over and under 70 but intergroup differences in magnesium and albumin levels were more marked in the elderly. These results do not support the postulated inverse relationship between vitamin C status and the risk of stroke.

Dietary Awareness of Children: Specific Food Items

A survey, conducted in ten secondary schools in Nottingham and involving 492 respondents aged 11‐16, examined the relationship between adolescents′ attitudes towards food components such as fat, protein and fibre and their attitudes towards the role of specific food items containing those components in maintaining a healthy diet. The results showed that attitudes towards selected food components tended to be held more strongly than attitudes towards foods containing those components. Thus whilst nearly 80 per cent respondents favoured a reduction in fat intake, only 45.8 per cent favoured a decrease in butter consumption. Attitudes towards specific food components and specific food items are a function of a number of complex inter‐related variables which require further investigation.

Consumer Survey of School Meals

A pilot survey was conducted at two secondary schools in Nottinghamshire in order to determine lunchtime arrangements, expenditure, factors affecting food choice, the popularity of other foods and eating‐out places, the satisfaction with the dining room and the reasons for not using the cafeteria. A total of 839 questionnaires completed by the children were analysed. The survey revealed a decline in the use of the cafeteria with increasing age. The amount spent at lunchtime was a significant factor in indicating whether the child had a school meal. Variety was the main factor affecting food choice. Future research will examine in greater detail the non‐cafeteria user in order to develop targeting strategies for increasing school meal uptake.

The Effect of BSE: Consumer Perceptions and Beef Purchasing Behaviour

Examines the perceptions of consumers towards beef and beef products following the 1990 outbreak of Bovine Spongiform Encephalopathy (BSE) and changes in purchasing behaviour by a survey, in 1991, of a total of 252 consumers in two locations. Results indicate that risk perceptions towards seven beef products varied and although this was not related to the age of consumers it did differ according to changes in purchasing behaviour at the time of the outbreak: 31.3 per cent of respondents changed their beef consumption at the time of the scare but the proportion of consumers persisting with consumption change fell over time.

Dietary Awareness of Children: Specific Food Components

Over the past few years several reports have been published recommending voluntary changes in UK diet in the interests of health. Major recommendations include a reduction in the consumption of fat, sugar and salt and an increase in consumption of fibre. A survey conducted in ten secondary schools in Nottingham and involving 492 respondents showed that adolescents between the ages of 11 and 16 generally favoured a decrease in consumption of fat and sugar and an increased consumption of fibre. However only half of the sample thought that salt intake should be reduced. There were significant differences in response based on the age and sex of the respondents. Reduction in fat and sugar intakes was a particularly dominant attitude amongst older girls, and this may be due to their concern over appearance rather than their concern for health.