The fat content was reduced by 36 per cent when doughnuts were prepared using 10 per cent of micro-particulated hulls, with no detrimental impacts on flavour, taste, crispiness, and general liking, says the study published in the Journal of Food Science .
"The recent trend toward reducing fat content in fried foods has been supported by the development of formulations with specific ingredients," explained the researchers from the Korea Food Research Institute and Korea University.
"Various ingredients such as alginates, powdered cellulose, methyl cellulose, soy protein isolate, and gums have been used," they added.
The use of soybean hulls has already been reported in cakes and cookies to reduce fat content of the finished formulation, according to background information in the article.
Moreover, the same researchers previously reported that the uptake of fat was reduced by about 25 per cent when added to the frying batter used for the production of potato sticks.
"Soybean hulls represent about eight to 10 per cent of the weight of soybean grain," wrote the researchers.
"Soybean hulls are inexpensive by-products of soybean processing and are high in fiber and low in energy and protein content.
Therefore, most soybean hulls have been used in animal feed."
However, the hulls could make a significant contribution to reducing the fat content of food products if further research supports the positive and promising early results.
Four different composites were prepared by dry-coating wheat flour with zero, one, five, and 10 per cent micro-particulated soybean hulls.
The resulting soybean hull-containing doughnuts were found to contain 11.5, 13.6, and 35.8 less fat, respectively, after deep-fat frying.
"Generally, when fat content decreases, sensory characteristics might be affected," explained the researchers.
"Although [doughnuts containing 10 per cent soybean hulls] showed a little low value in appearance, there was no significant difference in flavour, crispiness, taste, and general liking."
This showed that low-fat uptake fried products can be prepared with desirable sensory attributes by simply controlling the amount of soybean hulls used in the formualtion, they added.
"These results show that microparticulated soybean hulls may form a protective layer during frying process, and this process could be used by the food industry for preparing doughnuts with reduced fat uptake," concluded the researchers.
This study was funded by the Korea Food Research Institute.
Source: Journal of Food Science (Blackwell) Published online ahead of print, doi:10.1111/j.1750-3841.2008.00670.x "Preparation of Low-Fat Uptake Doughnut by Dry Particle Coating Technique" Authors: J.-S. Lee, B.-K. Kim, K.-H. Kim, D.-J. Park