Optimization of low-cost drying methods to minimize lipid peroxidation and determination of shelf life of Spirulina platensis (MI2) (Cyanobacteria) grown in the Philippines
2006
Tiburcio, P.C. | Galvez, F.C.F. | Cruz, L.J. | Gavino, V.C., Nueva Vizcaya State Univ., Bayombong, Nueva Vizcaya 3700 (Philippines)
Three low-cost drying methods (sun, solar and draft oven) were optimized to minimize lipid peroxidation in Spirulina platensis (MI2) during the drying process. Optimization in the pre-dehydration stage included the use of two antioxidants: alpha-tocopherol and tertiary-butyl hydroquinone (TBHQ) and two blanching methods: microwave and convective heat to inactivate enzymes. The efficiency of the pre-dehydration treatments in minimizing lipid peroxidation were evaluated in terms of the product's oxidative stability. The sample with the lowest TBA Reactive Substance (TBARS) value was considered the most stable. Of the two anti-oxidants, TBHQ was found to be significantly better than alpha-tocopherol in minimizing lipid peroxidation in heat-treated samples, while alpha-tocopherol was better than TBHQ in unblanced samples. Microwave blanching exerted a greater stabilizing effect than convective heat blanching. The combined effect of TBHQ and microwave blanching was found to be the most effective pre-dehydration treatment. Of the three inexpensive drying methods optimized, sun drying produced a dried product with a TBARS value closest to that of the spray-dried (control) sample. GLA degradation in Spirulina followed first-order reaction kinetics. At an accelerated temperature range of 45-55 deg C, the degradation rate constants (K sub r) of GLA obtained were 4.0 sup-2 to 8.8 sup-2/day. The energy of activation (E sub a) was 16.53 kcal/mol, and the Q sub 10 was 2.22. Based on 20 percent GLA degradation, the shelf life of sun-dried Spirulina at 30 deg C is 263 days or 8.6 months using the Arrhenius plot, and 258 days or 8.5 months using the Q sub 10 approach.
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