Stability offrozen Nigerian soups as affected by freeze-thaw cycles

The freezing and defrosting of frozen soups is a known practice among Nigerians and their stability is of utmost concern. Standard recipes were used to prepare selected traditional soups (‘ila’, ‘ogbono’, ‘ewedu’ and ‘kuka’ soups) of Nigerian origin. The influence of packaging materials (aluminium and plastics) and thawing conditions (microwave oven, ambient condition and hot water thawing) on the soups were determined by freezing them at -20 °C and thawing at the above conditions for four cycles at an interval of 5 days. At the end of each cycle, the free fatty acid, peroxide value, pH value, titratable acidity, viscosity, total plate counts and sensory attributes of the samples were determined using standard methods. Free fatty acid, peroxide value, pH, titratable acidity, viscosity and total plate counts of soups ranged from 0.56-3.09%, 5.82-14.54 mEq/kg, 6.53-7.17, 0.07-1.41%, 0.81-2.00 Pa·s and 1.50-2.92Log CFU/mL respectively. The nature of packaging materials and thawing conditions significantly influenced the stability indices of the soups at p<0.05. Limited deteriorative changes were observed in microwave-thawed soups in plastic containers, and were mostly preferred by panelists. The soups stability cannot be guaranteed if the number of cycle is above three, because of deteriorative increase in free fatty acid and peroxide values.