Lipase-catalyzed synthesis of structured lipids and their food applications
Fomuso, Lydia Bobimwo
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Structured lipids (SLs) were produced by acidolysis reactions in continuous stirred tank or packed-bed bioreactors. Food applications and physical properties of SLs were examined.|SLs were produced from olive oil and caprylic acid in a packed-bed bioreactor. The effect of solvent, temperature, substrate mole ratio, and flow rate/residence time were studied. Optimal solvent-free production of SL was obtained at a substrate flow rate of 1 mL/min, residence time 2.7 h, temperature 60 o C, and mole ratio 1:5 (olive oil: caprylic acid). SL produced at optimal conditions had 7.2% caprylic acid, 69.6% oleic acid, 21.7% linoleic acid and 1.5% palmitic acid at the sn-2 position. A total of 43% caprylic acid was incorporated into olive oil. Viscoelastic properties of mayonnaise and Italian salad dressing prepared with olive oil/caprylic acid SLs were studied using a SR5000, dynamic stress rheometer. Storage modulus (G’) and loss modulus (G”) were determined as functions of frequency, temperature, and stress. Both Italian dressing and mayonnaise samples displayed similar gel-like and viscoelastic characteristics.|Stearic acid was enzymatically transesterified with high-laurate canola using a nonspecific lipase from Candida antarctica to produce SLs suitable for margarine application. A stearic acid level of 30% was found to best match the melting characteristics of fat extracted from commercially available stick margarine. This SL was used to prepare nonrefrigerated and refrigerated margarine samples. Slip melting point, solid fat content, hardness index and some viscoelastic properties were determined for all samples. The effect of emulsifier type and concentration on oxidation, droplet size and creaming stability of a menhaden oil-caprylic acid structured lipid was evaluated. Oxidation was monitored by measuring thiobarbituric acid reactive substances, lipid hydroperoxides, and amount of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) left in the structured lipid. Emulsifier type affected the oxidation rate, but overall oxidation did not progress significantly enough to affect substrate levels. The effects of temperature, time, metal content, citric acid and a-tocopherol on the oxidation stability of a model oil-in-water emulsion were evaluated by response surface methodology. The relationship between variables differed depending on the type of metal catalyst used.