This investigation aimed to explore the antioxidant potential of date fruit extract using butter as an oxidation substrate on the basis of certain instrumental, orthodox analytical techniques and sensory characteristics. The objectives of this study were to characterize the date extract for polyphenolic compounds, free radical scavenging activity and inhibition of nitric oxide macromolecules and to study the effect of various concentrations of the date palm extract on oxidative stability and sensory characteristics.
The butter was added 200, 400 and 600-ppm respectively date palm extract and compared with a control, stored at refrigeration and ambient temperature during winter months for 90-days at the interval of 30-days. Peroxide value, anisidine value, iodine value, conjugated dines, totox value, free fatty acids and sensory evaluation were performed in the fresh and three month stored butters. Sensory evaluation of supplemented butter added with various concentrations of date palm extract stored revealed the effect of treatments, storage period and their interaction to be significant. Taste, Color and overall acceptability score was non-significant up to 30-days of storage. After this sensory score started to deteriorate and went on decreasing the rest of storage period. The decline in taste score was not due to the addition of date palm extract rather it was due to the generation of peroxides and other oxidation products. Oxidation products and peroxides are found to be in direct relation with temperature; with rise in temperature the decline in sensory evaluations was more pronounced. This connection between taste score and peroxide value was highly correlated (R= 0.9982).
The results of triplicate treatments and triplicate analysis (n=3x3; ±SD n=3x3) was analyzed by using one way analysis of variance techniques (ANOVA) to find out the effect of the date palm extract to the storage conditions. Differences among treatments were compared by Duncan Multiple Range Test.
Supplementation of butters with date palm fruit extract did not revealed any significant effect on the inhibition of free fatty acids (P>0.05). The free fatty acid content of fresh and 90 days stored treatments and control were at par with each other. The peroxide value of all the treatments and control increased during the storage period but to varying degree. The addition of date palm extract revealed a significant effect on inhibition of peroxide value (P<0.05). The peroxide value of fresh supplemented, control and 90 days stored samples showed a significant difference. The difference in control and treatments were in order of To > T 1 > T2 > T3 in 90-days stored experimental samples and control. T3 revealed a maximum resistance towards the increase of peroxide value during storage period of 90-days over the control at refrigeration temperature. It is evident from the result that the addition of date palm extract significantly inhibited the auto-oxidation phenomenon in butter stored at room temperature, however the concentration of oxidation products were higher as compared to butter stored at refrigeration temperature. The iodine value decreased during the storage period in control experimental samples throughout the storage period of 90-days but to varying extents at refrigeration temperature. Control (T0) showed highest decrease in iodine value while T3 showed least change in iodine value during the storage period.
The anisidine value of control and treatments stored at refrigeration temperature were in the order T0 > T1 > T2 > T3. Control revealed significant increase in anisidine value as compared to treatments. After 90 days of storage period the extent of secondary oxidation products in control and T3 was 22.24 and 8.35 at refrigeration temperature respectively. The classical rise of anisidine value was observed in all the treatments to varying degree, supplementation of natural antioxidant offered a great deal of resistance towards the rise of anisidine value. Supplementation of butter with date palm fruit extract revealed significant effect on the generation of oxidation products. Conjugated dienes for control and all the treatments increased throughout the storage time slowly and steadily.
Analysis of variance revealed that the effect of treatments, storage period and their interaction was significant. Taste, Color and overall acceptability score was non-significant up to 30-days of storage. After this sensory score started to deteriorate and went on decreasing the rest of storage period. The results indicate that ethanolic date palm extract at 600-ppm concentration can be used as natural antioxidant source for the long term storage of butter at ambient temperature during winter months. The outcome of this study will help the food industry for preservation of fats and oils.