Simple Wet Rendering Method for Extraction of Prime Quality Oil from Skipjack Tuna Eyeballs

Oil from skipjack tuna (ST) eyeballs is extracted by the wet rendering method at 121 °C for different holding times (5–60 min) using an autoclave. Yield increases as heating time increases up to 20 min (p < 0.05); no further increase is obtained with a longer heating time (p > 0.05). Conversely, acid value and total polar compounds increase. However, peroxide value (PV), thiobarbituric acid reactive substances, and anisidine value (AnV) decrease up to 30 min. No changes in unsaponifiable matter (UM) or conjugated diene (CD) are attained, regardless of heating time. Polar components (PC) increase with heating time (p < 0.05). All oil samples have a high polyunsaturated fatty acids (PUFA) content (40.46–41.00%), with monounsaturated fatty acids (MUFA) and saturated fatty acids (SFA) in the range of 20.94–21.26% and 37.77–38.45%, respectively. PUFA content is reduced slightly with a heating time of 60 min. Docosahexaenoic acid (DHA) (C22:6, n3) is the dominant fatty acid in all samples (31.67–32.24%). Based on FTIR spectra, heating for longer time results in lower intensity at wavenumbers of 3015 and 1740 cm^?1. Thus, light yellow oil from ST eyeballs prepared by a green process for an appropriate time can serve as an excellent source of DHA and other PUFA. Practical Applications: Tuna oil is known to be a rich source of DHA and PUFA with health benefits. However, precooked tuna heads, generally used as raw material, yield oils with a very dark color and offensive odor, which require several refinery processes. To reduce the number of steps in the refinery process, tuna eyeballs which are separated from tuna heads can render higher quality fish oil. Moreover, the wet rendering process, a green process without toxic substances, can be used without causing environmental problems.     

Characterization of fortified pasteurized cow milk with nanoliposome loaded with skipjack tuna eyeball oil

Nanoliposomes loaded with skipjack tuna eyeballs oil (STEO-NL) were prepared using an ethanol injection method, without and with the aid of ultrasonication. Higher amplitude (80%) and longer time (15 min) of ultrasonication reduced particle size (from 192.20 to 150.70 nm) and zeta-potential (from −40.43 to −47.29 mV) of STEO-NL but increased peroxide value (PV), conjugated diene (CD) and thiobarbituric acid reactive substances (TBARS) of STEO-NL. However, encapsulation efficiency was not different among all the samples (96.82-97.70%) (P > 0.05). Cow milk was fortified by addition of STEO-NL (without ultrasonication) at different final levels (0, 2.5 and 5.0% w/w). Subsequently, high-temperature short-time (72 °C, 15 s) process was employed to pasteurize the fortified milk, which were further stored up to 10 days at 4 °C. Microbiological quality and pH of pasteurized fortified cow milk were still acceptable. Addition of STEO-NL at higher level (5%) resulted in higher PV and TBARS and lower acceptability than the control and that fortified with 2.5% STEO-NL throughout the storage of 10 days, but sensorial acceptability was still obtained. In general, no differences in colour, and viscosity were attained among all samples. Moreover, pasteurized cow milk fortified with STEO-NL had an increased amount of n-3 polyunsaturated fatty acids.