N° 47 | July 2010

Preferences for Steaming of Vegetables

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The World Health Organisation (WHO) suggests eating at least five portions of Fruit and Vegetables (F&V) a day to reduce the risk of developing chronic diseases such as coronary heart disease and some cancers. Boiling continues to dominate amongst cooking methods for vegetables but steaming is preferable with fewer losses of water-soluble vitamins and other soluble beneficial components. A campaign to target steaming should demonstrate improvements in taste by providing samples to the public. Since some vegetables may show greater taste benefits than others, this study aimed to determine whether people prefer steamed vegetables and which might be the most appropriate to demonstrate this preference.

Material and Methods

Three types of fresh vegetables were cooked using three methods; boiling, steaming and microwave steaming. Similar sizes of each vegetable were cooked in 180g batches. Optimal boiling times for each vegetable found during a pilot study were 10, 5 and 7 minutes for carrot, cabbage and broccoli; times recommended for steaming were 7, 10 and 7 minutes respectively. Microwave steaming was carried out using Zip ‘n’ Steam bags at a high setting for 2 minutes. Each batch was held at 74°C for up to 30 minutes before presentation to subjects. Samples of 25g cooked vegetables were placed in coded polystyrene pots and presented to assessors in a Latin square to eliminate order bias. They rated each sample for appearance, texture, flavour and overall acceptability using a ninepoint (1–9) hedonic scale, and recorded how they usually cooked vegetables.

Preferences for steaming Vegetable

There were 35 females and 15 males, 80% of whom were aged 18–35 years. Steaming and microwave steaming were significantly higher rated than boiling for broccoli with regard to all features. In terms of acceptability the average scores were 6.2 and 7.1 for the two steaming methods and 5.1 for boiling (P < 0.001). Carrots were similarly considered better for flavour and overall acceptability. Cabbage was generally rated lower for all features and there were no differences amongst the cooking methods (for acceptability, scores were 4.9, 5.1 and 5.2, respectively). The question about the usual cooking method for vegetables was employed to group the subjects. The most common method was boiling, with 21 subjects using this method.

Mean scores for acceptability of steaming and microwave steaming were significantly higher for assessors who usually boil vegetables (5.5, 6.2 and 6.5, respectively) (P = 0.013). This was also found for those who usually stir-fry vegetables, but did not reach statistical significance for the few subjects who already steam vegetables.

Only 10% of the subjects who usually boil vegetables appeared to prefer the boiled vegetables.

Changing for steaming?

The findings obtained show that microwave steamed and steamed vegetables, with the exception of cabbage, were generally preferred over those that were boiled. It was also found that the majority of participants who boiled their vegetables at home did not prefer this cooking method when given a choice including steaming. Microwave steaming was marginally preferred over steaming, but the cost of the bags adds an inhibitory factor to the adoption of this more convenient method for many people.

If subjects can be persuaded to steam by giving samples of steamed broccoli, they might also steam other vegetables and consequently obtain the appropriate nutritional benefits.

There are however, many barriers to change that need to be taken into account in the promotion of steaming as a regular method for cooking vegetables, because sensory attributes may not be enough to convince many people to make a change.

A recent trend has been demonstrated in market research on sales and ownership of small kitchen appliances with sales of domestic electric steamers increasing from 480,000 units in 2001 to 700,000 units in 2006, an increase of 46.8%. However, ownership does not necessarily reflect usage. The same report shows that only 41% of those owning a steamer used it at least once a week. This indicates that there are barriers to the use of this equipment, even for those who have purchased and tried it. This study suggests that most people who currently boil vegetables would prefer steaming, especially if they taste broccoli, although the small numbers of subjects who already steam vegetables limit the conclusions that can be drawn about their preferences. More research is needed to understand the barriers to the adoption of steaming as a way of cooking vegetables

Rennie, C. & Wise, A. (2010) Preferences for steaming of vegetables. J. Hum. Nutr. Diet. 23, 108-110.

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