"The rapeseed protein concentrates showed interesting properties such as better taste and aroma... This information is important in order to be able to customize rapeseed proteins for specific uses for human beings," wrote lead author Yumiko Yoshie-Stark from the Tokyo University of Marine Science and Technology and the Fraunhofer Institute for Process Engineering and Packaging, Freising, Germany.
Rapeseed, palm oil and soybean are all experiencing strong market growth as food makers continue to turn away from animal fats in favour of vegetable alternatives. By 2008 analysts Business Communications Company predict these key vegetable edible oils will account for 70 per cent of the US market alone.
After oil removal however, almost 60 per cent of the waste mass ends up with a protein content of about 65 per cent. This is mostly used in animal feed but, say researchers, could be "a source of new food ingredients" with potential functional and health properties.
The new research, published in the journal LWT Food Science and Technology (Vol. 39, pp. 503-512), used two rapeseed cultivars Lion (from Creol, France) and Express (from Cetion, France) in the formulation of sausages. The Express cultivar is said to be one of the most commonly used varieties in European research.
The sensory aspects of the finished products were compared with sausages made with one of two commercial soy proteins (concentrate or isolate), as well as the control sausage made with casein.
Functional properties such as water binding capacity, oil-binding capacity, and emulsification capacity and stability using standard methods from the American Oil Chemists Society (AOCS) and the American Association of Cereal Chemists (AACC).
The sausages, prepared by food processing company Rovita GmbH in Germany, contained 21 per cent pork, 21 per cent beef, 25 per cent pork lard, and 29 per cent ice cubes, per 100 grams. The protein content was kept constant at two grams per 100 grams for each of the protein sources used.
The water-binding capacity of the steamed Express protein was 4.2 ml/g, and 4.85 ml/g for the Lion cultivar. The rapeseed meal was steamed in order to deactivate the enzyme myrosinase, which decomposes glucosinolates and creates a bitter taste in the plant material.
The oil-binding capacities of the steamed Express and Lion cultivars were measured to be 3.8 and 4.7 ml/g, respectively.
The emulsification capacity for the steamed cultivars was between 325 and 333 ml/g at pH5. Compare this to the egg white emulsification capacity of 800 ml/g and it is clear that the rapeseed protein value is significantly lower.
When formulated into sausages and eaten, the rapeseed protein-containing sausages produced favourable sensory profiles.
"Considering the sensory attributes that were assessed, the sausage prepared with rapeseed protein had significantly superior taste and aroma attributes but significantly poorer texture and colour than the control sausage sample," said the researchers.
Soybean proteins produced sausages with better colour but inferior taste, said Yoshie-Stark.
"This result shows that sausage quality was strongly affected by two per cent protein replacement in the sausage formulation It may be possible to further modify or improve the rapeseed proteins for application in meat/sausage products," concluded the researchers.
On-going research could yet find a human application for the rapeseed protein, particularly given the favourable sensory results from these preliminary applications. According to the USDA, rapeseed is the second leading source of protein meal, although this is mostly used in animal feed.
According to FAO statistics, the global rapeseed production in 1965 was only 5.2m metric tonnes, but rocketed to 46m metric tonnes in 2005, with China leading the world in terms of production (13m metric tonnes).