Process optimisation and quality evaluation of fruit incorporated synbiotic ice creams.

Abstract

Probiotics are live microorganisms that benefit human or animal health by maintaining or enhancing intestinal microbial balance. Prebiotics are non-digestible food ingredients that promote host health by selectively stimulating the growth or activity of beneficial bacteria in the colon. Synbiotics is the combination of probiotics and prebiotics to improve the survival and function of beneficial gut microorganisms. The utilisation of locally available fruits, such as banana, mango and jackfruit, attracts consumers by diversifying the sensory attributes of products while enhancing nutritional value. Hence, the study was proposed to standardise fruit incorporated probiotic ice creams with Lactobacillus acidophilus, develop synbiotic ice creams with suitable prebiotics and evaluate the acceptability, nutritional and shelflife qualities of the developed ice creams. In this study, fruit incorporated ice creams were standardised, where the plain ice cream was the control. The treatments (T1 -T36) included the addition of fruits (mango, jackfruit and banana) in the form of pulp and osmodehydrated bits in ice cream. The addition of the fruits varied from 5 to 30 per cent by weight. A panel of fifteen judges evaluated all the prepared ice creams for their organoleptic quality using a nine-point hedonic scale to assess the sensory attributes viz appearance, colour, flavour, texture, taste and overall acceptability. Using Kendall's coefficient of concordance, the mean scores for the organoleptic parameters of each treatment were analysed statistically. As per the organoleptic score, the overall acceptability for sensory attributes was highest for treatment T2 with 10 per cent mango pulp based ice cream (overall acceptability score-8.46). Among the mango pulp incorporated ice creams, it was noted that, with an increase in the addition of mango pulp the colour, taste and flavour became intense which adversely affected the overall acceptability of the ice cream. The treatments T7 - T12 were the addition of mango bits (MB) incorporated ice creams among which T8 with 10 per cent MB scored highest overall acceptability score of 8.57. The treatment T14 (10% jackfruit pulp incorporated ice cream) and treatment T20 (10% jackfruit bits incorporated ice cream) had an overall acceptability score of 8.81 and 8.45 respectively. The treatment T25 (5% banana pulp incorporated ice cream) and treatment T31 (5% banana bits incorporated ice cream) received the highest acceptance with overall acceptability scores of 8.61 and 8.51 respectively in organoleptic evaluation. The selected best treatments were taken for further studies. The probiotic, Lactobacillus acidophilus (DVS culture) was utilised for the development of fruit incorporated probiotic ice creams. The rate of inoculation of probiotic culture into ice cream was evaluated by varying the concentrations of L. acidophilus at 1g (T1), 2g (T2) and 3g (T3). All treatments had optimum viability, and the rate of inoculation was highest for T3 with viable counts of 10.25 log CFU/ml for mango pulp and bits based ice cream, 10.26 log CFU/ml for jackfruit pulp and bits based ice cream and 10.26 and 10.25 log CFU/ml for banana pulp and bits based ice cream respectively. The organoleptic evaluation of all the fruit incorporated probiotic ice creams was done on a nine-point hedonic scale and the highest scores for organoleptic parameters were obtained for T1 (1g addition of L. acidophilus). The stage of addition of L. acidophilus to ice cream (before and after ageing) and time of incubation (15 min, 25 min and 30 min) were also assessed. An increase in the viable count of L. acidophilus was observed after ageing and with an increase in the incubation time. Irrespective of the form in which the fruit is being added, an overall acceptance score exceeding 8 on a nine-point hedonic scale was achieved when the probiotic culture was added after ageing (24 h at 4ºC) and the incubation time was 15 min. Hence, the optimised conditions for the development of fruit incorporated ice creams was the addition of one gram of L. acidophilus added after ageing, incubated at 15 min for all the fruit incorporated probiotic ice creams. The probiotic culture, L. acidophilus was inoculated to fruit incorporated ice creams in the optimised conditions (1g, after ageing and 15 min incubation) and the organoleptic evaluation was done and compared with its non probiotic controls. The results show that all treatments, including controls and probiotic ice creams, received scores above 8 on the nine-point hedonic scale, indicating high acceptability among judges. All the developed fruit incorporated probiotic ice creams along with their controls were kept in food grade polypropylene containers maintained in frozen conditions for three months and quality analyses were conducted. The physico-chemical qualities of the fruit incorporated probiotic ice creams were analysed using standard procedures. The initial moisture content in fruit pulp incorporated probiotic ice creams ranged from 60.41-64.04 per cent and 57.10-60.87 per cent respectively which decreased to 59.22-60.75 per cent and 53.25-57.97 per cent by the end of storage. A similar significant decrease was also observed in fruit bits incorporated ice creams. A significant increase in meltdown time, weight per litre, viscosity and TSS and a decrease in reducing sugar was observed during three months of storage among all the fruit incorporated probiotic ice creams. The water activity, pH, acidity, carbohydrate, protein, fat, fibre, energy, minerals, in vitro digestibility of proteins and in vitro availability of minerals were also analysed. The mean score for overall acceptability in the organoleptic evaluation of prepared ice creams remained 8.70 and above even after a decline by the end of the storage period. The viability of L. acidophilus in all the fruit incorporated probiotic ice creams decreased to 9.43-9.56 log CFU/ml in the third month of storage period but maintained the optimum viable count as per FSSAI standards (above 8 log CFU/ml). The total bacterial count of fruit incorporated probiotic ice creams ranged from 7.08 to 7.13 log CFU/ml, with fruit pulp variants showing higher bacterial count than fruit bits based ice cream. E. coli and total coliforms were undetected in all developed ice creams. Fungal colonies and yeast growth were also absent for up to three months of storage. The prepared fruit incorporated probiotic ice creams, was enhanced with the addition of prebiotics viz inulin and honey, to develop fruit based synbiotic ice creams. The prebiotic ingredients were incorporated at varying concentrations (1, 2 and 3g) into the selected probiotic ice creams. The optimum level of addition was determined by sensory evaluation. The addition of 1g of inulin and honey were selected for further studies as it received highest overall acceptability scores (8.76-8.83 on nine point hedonic scale). The optimisation of growth conditions of L. acidophilus was evaluated for synbiotic ice creams incorporated with both inulin and honey. The rate of inoculation (1, 2 and 3g of L .acidophilus), stage of addition (before and after ageing) and time of incubation (15 minutes, 25 minutes and 30 minutes) were assessed. It was concluded that the addition of 1 gram of L. acidophilus, inoculated after the ageing (24 h, 4ºC) of ice cream and incubated for 15 minutes was the best condition for the development of fruit incorporated synbiotic ice creams (both inulin and honey) with an optimum viable count 10 log CFU/ml and above. The prepared synbiotic ice creams had a high sensory score 8.28 and above for all the treatments compared to the control. The moisture and weight per litre in honey based ice creams (57.10-65.01%) were higher than that of inulin based ice creams (56.78-64.93%). By the end of storage, a decrease in moisture and an increase in the weight per litre was observed. The viscosity tends to increase over time and the highest initial viscosity was observed for banana bits incorporated synbiotic inulin based ice creams (428.93cP). TSS was higher for inulin than honey based ice creams and was increased during storage while reducing sugar and total sugar was higher for honey based ice creams and decreased during storage. The mean score for overall acceptability in organoleptic evaluation during storage decreased and the least observed value was 8.70. The viability of L. acidophilusdeclined but maintained a viable count at 9.47 log CFU/ml and above during storage. The total bacterial count of fruit incorporated synbiotic ice creams was within the range of 7.08 to 7.13 log CFU/ml. Fungal colonies, yeast, E. coli or coliforms were not detected in the synbiotic ice creams during storage. The cost of production of the developed ice creams ranged from Rs.45 to Rs. 64/- of which the cost of synbiotic ice creams was the highest. The study revealed that fruit based ice creams can be developed with the addition of 10 per cent mango pulp, mango bits, jackfruit pulp, jackfruit bits and 5 per cent banana pulp and banana bits. Fruit incorporated probiotic ice creams can be successfully developed with addition of 1g L. acidophilus incorporated after ageing and incubated for 15 minutes. The fruit incorporated synbiotic ice creams can also be developed with the incorporation of prebiotics like inulin (1g) and honey (1g), with the inoculation of L. acidophilus (1g), after ageing (24h, 4ºC) and incubated at 15 min. The developed probiotic and synbiotic ice creams had higher organoleptic scores, and good nutritive value, which maintained an optimum probiotic viability. The development of a successful formulation for fruit incorporated synbiotic ice creams is desirable, as such products would meet commercial quality standards and can be considered as functional foods.