OMEGA-3 FORTIFICATION OF SAUCES

Fish oils containing omega-3 (ù3) fatty acids are known to provide beneficial health effects and are added to various foods to improve their nutritional status. This research investigated the challenges of incorporating two types of ù3 fish oil preparations into two commercially available fish sauces, namely abalone and oyster sauces, and examining the effects of such additions on sauce properties, acceptability and storage life. The ù3 supplements both contained eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The first ù3 supplement was refined non-winterised tuna oil and the second was microencapsulated tuna oil in which the oil was contained in microcapsules composed largely of caseinate. Both of these oils were incorporated at two levels of ù3 fortification in accordance with the guidelines of the Australian and New Zealand Food Authority Food Standards Code 2004. Fortification increased the fishy taste of the sauces, which was: (a) more pronounced in the fortified abalone sauce than in the fortified oyster sauce; and (b) more pronounced in sauces fortified with refined non-winterised tuna oil than sauces fortified with microencapsulated tuna oil. Fortification of the sauces with the latter at the lowest level for a fortification claim of equivalent to no less than 30 mg total EPA and DHA per 30 g serving was found not to cause any significant difference in taste or preference between fortified and unfortified sauces used as controls. However, sedimentation and oil separation occurred. Morphological studies found this the result of disintegration of the microcapsules caused by precipitation of the caseinate in the encapsulation material at the pH of the sauces (4.5 5.2). The microencapsulated tuna oil was homogenized under different conditions to reduce the particle and oil globule sizes. The optimum fortification process was prior-homogenising the ù3 ingredient in water for one minute at 3000 rpm and adding it at the beginning of processing and cooking together with all other ingredients to a sauce. During a scale-up pilot production, thinning (in both fortified abalone and oyster sauces) and dramatic separation (within two weeks of accelerated storage of the fortified abalone sauce) occurred. Image analysis revealed the absence of starch in the separated phases of the fortified abalone sauce. Amylase was detected in the microencapsulated oil and its activity traced to two materials used for its encapsulation. The enzyme had an optimum activity at pH 5.4 and had 10 times higher activity at pH 5.19 (pH of the fortified abalone sauce) than at pH 4.55 (pH of the fortified oyster sauce). A laboratory experiment was carried out to modify the process of the pilot production. The modified process was scaled up for a second pilot production to produce a second batch of abalone sauce. It involved (a) changing the order of adding the prior-homogenized microencapsulated tuna oil i.e. adding it to partially cooked sauce at 85oC instead of adding it at the beginning of processing and cooking with all ingredients to a sauce, and (b) lowering the pH of the fortified abalone sauce from 5.2 to 4.8. The amylolytic effect of the heat-stable amylase during cooking was reduced and this led to marked product improvement and shelflife extension. Thinning no longer occurred and the fortified abalone sauce showed no decrease in sensory scores during 32 weeks at 35oC and 46 weeks at ambient. At 64 weeks at ambient the product still appeared stable, i.e. the Q10 was 2. No loss in total EPA/DHA was found. In contrast, the fortified oyster sauce of the first pilot production showed decreases in viscosity and sensory scores during storage and reached the end of its shelf life at 12.5 weeks at 35oC and 26 weeks at ambient, i.e. the Q10 was 2.1. There was a near complete loss in total EPA and DHA content. In a study to replace citric acid with ascorbic acid to serve the possible multiple functions of acidification, antioxidation and nutritional enhancement, 0.16 % ascorbic acid in fortified abalone sauce accelerated sauce separation. Its incorporation in abalone and oyster sauces (0.16% - 0.5%) reduced the Rancimat induction periods by 3- 21 times, compared with the respective sauces containing citric acid used as controls. Of the two sauces fortified, the fortification of oyster sauce was found to be less demanding. There were fewer taste, appearance and stability problems, attributed to the sweeter characteristics of the oyster sauce which helped to mask the fishy taste. The use of caramel as a second thickener also made thinning due to starch hydrolysis by amylase less pronounced. By comparison, fishy odour and taste were more detectable in the fortified abalone sauce due to the inherently fishier and less sweet characteristics of this sauce. This sauce was also more prone to separation as it depended primarily on starch as a thickener. The above findings would be of benefit to the sauce industry. Particularly, the optimal fortification process would reduce costs and wastage for any manufacturer planning to embark on ù3 fortification of sauces. Furthermore, various aspects of the above findings should be of interest to the food industry as a whole. For example, the finding that losses in total EPA & DHA paralleled reduction in viscosity would assist low viscosity food processors to pre-empt problems arising from losses of the ù3 fatty acids when embarking on ù3 fortification