Stephen D. Kelleher

Effect of NaCl on catalysis of lipid oxidation by the soluble fraction of fish muscle

Sodium chloride stimulated catalysis of oxidation of phosphatidylcholine liposomes by the soluble fraction of mackerel muscle. Chloride was determined to be the active component of the salt in this system. Sulfate also stimulated lipid oxidation. No difference was observed with either anion among sodium, potassium, or lithium cations. Redox iron was involved in the chloride stimulation of lipid oxidation by the press juice. Part of the chloride stimulation of the press juice was mediated through the high molecular weight (greater than 5 kdalton) fraction. Chloride improved the pro-oxidative effect of ascorbate on rat liver ferritin in vitro. It did not appear that production of chlorine radical by peroxidase was involved in the stimulatory effect of chloride.

Lipid oxidation in seafoods under conventional conditions

Abstract The N‐3 fatty acids in mackerel and cod were not significantly oxidized by baking, broiling or pan frying. However, major amounts of the fish oil were physically lost during cooking. The concentration of the N‐3 fatty acids in the oil released was significantly reduced, demonstrating the possible sensitivity to oxidation once the oil is removed from its natural state. When pollock was deep fat fried without batter, extensive absorption of the frying oil occurred. Batter coating appeared to protect the fillets against loss of moisture, absorption of cooking oil and dilution or loss of flavor volatiles. Frying fish may accelerate or delay oxidation of oil heated to frying temperatures, depending on the conditions of frying. Oxidation of cholesterol in squid occurred upon exposure to the sun and UV and IR lamps.

Functional fish protein isolates prepared using low ionic strength, acid solubilization /precipitation

Abstract A technique was developed, whereby proteins from animal muscle tissue were solubilized under conditions of low ionic strength and low pH, that retained high yields of proteins, which when precipitated and neutralized were capable of producing gels with good functional properties. Gels made from acid-solubilized proteins commenced gelation at a substantially lower temperature when compared to washed muscle. Fluorescence data suggests extensive protein unfolding at pH values between 5.0 and 3.0, whereupon further acid addition in the range 3.0-2.0 resulted in a re-folding of the proteins. Extensive unfolding of the protein appears to be crucial to the development of a gel upon precipitation and neutralization.

Gelation properties of fatty fish processed with or without added sodium chloride, cryoprotectants and antioxidants

Abstract The effect of 3% (w/w) added salt; an antioxidant mixture consisting of 0·02% (w/w) t-butylhydroquinone (TBHQ) (based on total lipid), 0·2% (w/w) ascorbate and 0·2% (w/w) sodium tripolyphosphate (STPP) added during the grinding and washing steps; and a cryoprotectant mixture of 4% (w/w) sorbitol, 4% (w/w) sucrose, and 0·2% (w/w) STPP added just prior to gel formation were tested for their effects on true strain and stress at breakage and fold test scores of washed bluefish and mackerel mince. The addition of 3% (w/w) NaCl and the cryoprotectant mixture increased true strain values under all conditions; fold test scores followed similar patterns. The antioxidant mixture gave increased strain values in the absence of the added 3% (w/w) NaCl in both bluefish and mackerel prepared with or without cryoprotectants; in the case of mackerel, the antioxidant mixture gave higher true strain values in the presence of salt as well. Stress values were highly variable and no clear trends were observed with bluefish with any of the parameters; seven out of eight samples of mackerel had lower stress values in the presence of the antioxidant mixture. The results may be useful in designing a process for improving the gelation characteristics of fatty fish.

Changes in Red Hake (Urophycis chuss) Muscle Induced by Different Freezing Strategies

The effect of single and double freezing at −20°C on fresh and aged red hake with two different holding times of the thawed fillets between the first and second freezing treatments was determined. In addition, twice-frozen fresh red hake was treated with two antioxidation systems to assess their effectiveness in reducing lipid oxidation. Fresh, untreated red hake at 0 time was used for comparison. Significant dimethylamine (DMA) production occurred with all frozen samples, and the differences were not marked after 7-month storage. With a storage time of 3 months, however, there were differences between the treatments in both the fresh and aged samples with the once-frozen sample producing the least DMA, the twice-frozen sample with the 24-h holding time between freezings the most, and the twice-frozen sample with a 6-h holding time between freezings giving intermediate values. All samples showed a greater than 50% loss in protein solubility as determined by lithium chloride extraction after 3 months of storage, and the protein solubility declined further when samples were tested at 7 months. Samples with the best (once-frozen fresh) and worst (twice-frozen with 24-h holding time between freezings of 5-day aged muscle) treatments had the highest thiobarbituric acid-reactive substances (TBARS) values. Both antioxidant treatments were effective in reducing TBARS development.

Characteristics and Storage Stability of Atlantic Hagfish

Abstract Atlantic hagfish (Myxine glutinosa)is harvested primarily for its skin. The meat is not widely accepted as a food in the U.S. due to its crunchy, rubbery texture and its visually unattractive cartilaginous notochord. Hagfish meat contained 14.3% protein, 4.6% lipid, 0.9% ash, and 80.1% moisture. Monounsaturates comprised almost two-thirds of the total fatty acids. C22:5 was found at higher levels than the more common n-3 fatty acids, C20:5 and C22:6. Odors from refrigerated storage, described as “earthy,” persisted for approximately 2 days and were subsequently followed by “sweet” and “fresh.” Over extended frozen storage (- 10, -20) TBARS reached levels found in rancid products; however, sensory analysis was unable to detect typical rancid odors. Antioxidants were successful at reducing TBARS values in muscle frozen at commercial temperatures.