The effect of milk protein concentrate (MPC) at 0, 2, 4, and 6% on lipid oxidation and volatile formation in frozen stored herring mince (-18 degrees C) was evaluated by analyzing samples at 0, 2, and 4 months for fatty acid composition, volatiles, and thiobarbituric acid reactive substances (TBARS). Sensory evaluation was also conducted to assess the intensity of fishy odor, and the volatiles were analyzed using static headspace gas chromatography-mass spectrometry (SHGC-MS). The addition of 4 and 6% MPC to herring mince resulted in a 33% and 50% reduction of TBARS, respectively, at month 4 and lessened the intensity of fishy odor throughout storage. However, MPC did not protect fatty acids from enzymatic degradation unless it was added immediately after mincing. Volatile analysis using SHGC-MS showed that 4% MPC was able to reduce headspace volatiles associated with fishy odor. MPC is most effective for reducing 4-heptenal, 3-methyl-1-butanol, 2-hexenal, and 1-penten-3-ol, which are known to be potent odorants associated with lipid oxidation.

In developing mince-based nugget products using mackerel, an abundant, underutilized, high omega-3 fatty acid species, attention was given to moistness and texture improvement with moisture-releasing ingredients. Three basic approaches were used: added water level variation (0 to 35%), varying added water-moisture-releasing vegetable combination (28/0, 21/7, 14/14, 7/21, 0/28), and varying milk-water combination (0/21, 7/14, 14/7, 21/0). Main ingredients of nugget included mackerel mince, mild cheddar cheese, and hydrated textured soy protein concentrate. The formulated products were molded, lightly battered, flash fried, and frozen until tested. Frozen nuggets were cooked to 65 degrees C and subjected to the Instron texture analysis (compressive force CF at 70% deformation, expressible fluid EF) and sensory analysis (firmness F, moistness M, overall desirability OD). The 28% added water, 7% moisture-releasing vegetable at 21% water, and 14:7 and 21:0 milk-water combinations were preferred (P < 0.05). Among the vegetables, onion and mushroom were preferred. Positive correlations were M-OD (r= 0.82), EF-OD (r= 0.54), and EF-M (r= 0.49), and negative correlations were F-OD (r=-0.83) and CF-OD (r=-0.34). Milk was more effective than water in rendering moistness and tender texture. The vegetable was effective in forming and making the cooked product moist with less liquid added by holding moisture release during forming and liquid cells after cooking. During warming under the lamps, the least decreases in sensory score, compressive force, and expressible fluid were observed in nuggets made with vegetable and milk.

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