Rheological Properties of Some Fruit Spreads

Rheological properties of three Smooth homogenized spreads were evaluated at different shear rates (2.29 – 34.35 s -1 ) using Brookfield rotational viscometer (DVIII Ultra). The spreads were prepared from purees of three fresh fruits, (Guava, Banana and Strawberry). To 100 g of puree; 1 g citric acid, 2 g sugar, 10 g water and 1g of a thickening agent were added and the mixture was homogenized. Xanthan, guar and carboxy methyl cellulose (CMC) gums were used for making three guava spreads, whereas xanthan only was used for making banana and strawberry spreads. Different rheological models were fitted to the data. The effect of temperature on rheological properties of guava, banana and strawberry spreads was studied. All fruit spreads, exhibited non-Newtonian pseudoplastic behavior. Herschel-bulkley (HB) model was the best fit (i.e. highest R 2 ) for data of guava and strawberry spreads followed by Casson and Power law models. Bingham model showed higher values for yield stress of all spreads than those of HB model, whereas those of Cassons’ were the least. Guava spread containing xanthan was more viscous than those containing guar or CMC. In general, spread viscosity decreased as temperature was increased. Heat penetration tests conducted on xanthan-containing spreads packed into flexible PA/PE pouches suggested possible use of such pouches for packaging fruit spreads. Xanthan-containing spreads when subjected to sensory evaluation gained satisfactory scores or butter which indicated panelists’ appreciation for the new products.