Utilization of tuna roe and using inulin as oil replacer for producing value added omega-3 mayonnaise product

Abstract

Background: The fishery industry has been important for Thailand’s economy for more than 30 years. For example, Thailand is the world’s largest canned tuna producer and exporter. However, only ordinary meat or white meat is used for raw material in canned tuna products. While roe, viscera, head and dark meat are sold at cheap prices, with these by-products being used to feed plant or local human food, its nutritive values with fat, protein and minerals are still high. It is well known that tuna is a good source of polyunsaturated fatty acid (PUFA), including Eicosapentaenoic acid (EPA) and Docosahexanoic acid (DHA). People around the world pay more attention to eating salads consisting of fruits and vegetables, in addition to dressing. Generally, mayonnaise, a kind of salad dressing, consists of chicken egg yolk (12-15%) and soybean oil (30-65%). Both of these ingredients contain very high saturated fatty acid contents. Therefore, because normal mayonnaise is high in fat content and low in polyunsaturated fatty acid, this product is not ideal for people on a diet or those who are trying to control their weight. Objective: To increase omega-3 through tuna roe substitution and to replace fat content using inulin gel. Methods: Tuna roe was prepared by soaking in galangal solution extracted with 95% ethanol for removal fishy/rancidity odor. Inulin powder 45 g was suspended in 55 ml of water before being brought to heat at temperature 80oC for 30 min to form a gel and stored at 4oC. Treatment of making omega-3 mayonnaise product was started using 100% tuna roe substitution for egg yolk. Thereafter, inulin gel was added to replace vegetable oil at 0, 25, 50, 75 and 100%. Basic mayonnaise containing egg yolk and 0% inulin gel (100% soy bean oil) was used as the control sample. Color and emulsion stability tests were monitored for physical quality. pH value, peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were used for chemical quality analyses. Total viable count (TVC), yeast and mold, lactic acid bacteria (LAB) and coliforms were measured for microbiological quality. Sensory evaluation using 9-point hedonic scale technique was also monitored. Results: When there was increased inulin gel in the mayonnaise, L* value significantly increased while a* and b* values significantly decreased (p<0.05). Without addition of inulin gel, tuna roe mayonnaise (IG0) had lower emulsion stability compared with control sample containing egg yolk. It was found that using the inulin gel significantly increased moisture contents and water activity of the mayonnaise. However, there was no significantly difference found in pH value in any sample. In addition, the tuna roe mayonnaise with and without added inulin gel possessed higher lipid oxidation products determined as PV and TBARS value compared with basic mayonnaise using egg yolk (control sample). All microbiological quality indices were very low and passed through a standard regulation of mayonnaise product. Although consumer acceptability of the mayonnaise producing from tuna roe was lower than that of control, 50% of inulin gel substitution (IG50) seemed to obtain higher sensory score when compared with other inulin gel substitution groups. Therefore, sensory improvement of the tuna roe mayonnaise product substituted with inulin gel needs to be studied further. Conclusions: The mayonnaise produced from tuna roe and replaced fat with inulin gel between 25 to 100% were successful when determined by emulsion stability, pH value and microbiological quality. However, sensory score of the mayonnaise using 100% tuna roe with and without inulin gel substitution was lower than that of control. The tuna roe mayonnaise substituted with 50% inulin gel (IG50) should be selected for sensory improvement in the further work.