Currently, only three in 10 adults are achieving the five-a-day target, according to the National Diet and Nutrition Survey in 2018. Increasing vegetable consumption would bring many benefits to the population’s health, reducing risk of heart disease, protecting against type 2 diabetes and some cancers.
At the same time, food waste throughout the food chain is a major issue that needs to be addressed. Estimates suggest over a third of fruit and vegetables produced in the UK is wasted due to cosmetic reasons.
So could freeze-drying solve both these problems simultaneously?
Get your bread around this
Researchers at Aberdeen University have been exploring the use of freeze-dried vegetables such as carrot, tomato, beetroot and broccoli in bread. Viren Ranawana, research fellow at the University of Aberdeen, led the research, which looked at the impact on the nutritional and antioxidant implications, as well as the effect on shelf-life, product quality and oxidative stability during storage and digestion.
“We don’t want to discourage people from eating fresh vegetables,” clarified Ranawana. “Using freeze-dried vegetables in products such as bread can be a stepping stone in encouraging people to try out and become more familiar with different vegetable flavours.”
In the research, 10% of flour was substituted with freeze-dried vegetable powder, which resulted in a fresh vegetable equivalence of 300-900g in an 800g loaf. In other words, the equivalent of 30-90g of fresh vegetables in two slices of bread.
Nutritional and health benefits
Freeze-drying fruits and vegetables provided a nutritionally superior product compared to hot air drying, according to the study. Additionally, adding these ingredients to bread improved the nutritional and antioxidant properties.
All the vegetable breads had significantly higher antioxidant capabilities compared to plain bread, though the beetroot bread showed the greatest potential.
These loaves also had significantly higher fibre contents compared with the plain bread, with all four varieties having over 6g of fibre per 100g. With only 13% of men and 4% of women currently meeting the recommended fibre intakes, these breads could help increase those figures while also helping to introduce more diversity to diets – something that would be great for gut health as well as overall health.
Another nutritional bonus was that the mineral content was significantly higher compared with plain bread, delivering antioxidant vitamins such as vitamin E and carotenoids.
Let’s get functional
Bread with beetroot and broccoli appeared to have an improved storage life, evidenced by better texture-retention properties.
The research showed little difference in hardness of the fresh tomato, carrot and beetroot breads compared to the plain bread, which suggests their addition had minimum effects on texture.
The broccoli bread did not seem to prove as well as the other bread and consequently had a higher density of crumb and greater initial hardness in the loaf.
Beetroot consistently showed positive functional effects such as storage and digestion, and could be particularly beneficial to add to bread.
Freeze-dried fruits and vegetables appear to have signiﬁcant but as yet untapped potential as an ingredient in a wide range of foods. Ranawana pointed out that “they could be used to improve nutritional quality, product stability as well as offering a variety of natural ﬂavours and colours. They could also play a useful role in the formulation of speciality products such as low-gluten or gluten-free and vegan foods.”
“There are many potential opportunities that these ingredients could enhance product quality and function,” says food technologist Sheila Küpsch, who has worked with freeze-dried fruit and vegetable powders. “For example, freeze-dried carrot could enhance the nutrition, colour and consistency in vegan scrambled egg."
Of course, when incorporating freeze-dried vegetables into products, the key question is taste. If consumers develop a taste for less sweet and more savoury products, then this could be an exciting area for product development, for example: vegetable desserts, savoury yoghurts and baked goods.