Optimisation of the formulation of fibre incorporated reduced calorie herbal rasmalai

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India's market potential and current growth rate of traditional dairy products is unparallel and all set to boom further under the technology of mass production.Dairy industry is looking forward to develop functional products such as low-calorie herbal products (Singh and Singh, 2014).Sucralose is a zerocalorie artificial sweetener with very little after taste as compared to other artificial sweeteners and provides good acceptance to the products.Rasmalai is a chhana based dairy dessert served by dipping in sweetened concentrated milk and in chilled condition.It is a very delicate, spongy and chewy sweet that has a delectable taste (Aneja et al., 1990;Sharma, 2004;Ambili et al., 2023).
In view of above an attempt was made to develop a process for manufacturing of dietetic herbal rasmalai with the incorporation of herbs viz., tulasi, ashwagandha root powder and isabgol (dietary fibre) and reducing the calorie of the product by replacing cane sugar with sucralose in concentrated milk so that it could be a new value added and functional product for dairy and food industry.The proposed objective of the formulation is to develop a product with enhanced nutritional benefits which might offer same delicacy as a traditional ethnic food.

Preparation of fibre incorporated herbal rasmalai
Cow and buffalo milks required for the manufacture of rasmalai was procured from Dairy Plant, Kerala Veterinary and Animal Sciences University (KVASU), Mannuthy.The rest of the ingredients including dried tulasi leaves, ashwagandha root powder and isabgol were purchased from the local market, Mannuthy, Thrissur.Rasmalai was prepared as per the procedure standardised by Sharma (2004) and Ambili et al. (2023) with slight modifications.Standardised cow milk (3.2% fat and 8.3% SNF) was coagulated with citric acid (2% concentration) to obtain chhana.Later, isabgol as dietary fibre (0.583%), tulasi extract at 6.951% (3 ○ Bx) and ashwagndha root powder (0.423%) was added based on the weight of chhana.Flattened chhana balls (15-20 g) were portioned and cooked in sugar syrup (50 °Bx) for 15-20 minutes and then soaked in sugar syrup of 40 ○ Bx for 20 minutes.Sweetened concentrated milk (buffalo milk concentrated to 1/3 rd of initial volume) for the soaking of rasmalai balls was prepared by replacing the sugar completely with sucralose at different levels like T2 (100 ppm), T3 (200 ppm), T4 (300 ppm) and T5 (400ppm).The treatments were compared with T1, control (5% sugar) and the obtained sensory scores were subjected to statistical analysis (Kruskal Wallis) and the best level of sucralose was selected and the rasmalai balls were dipped in the selected milk.

Sensory attributes of fibre incorporated reduced calorie herbal rasmalai
Sensory evaluation was performed by a panel of five semi expert judges from Department of Dairy Technology, Verghese Kurien Institute of Dairy and Food Technology, KVASU, Mannuthy, Thrissur (India).Samples for analysis were coded with three-digit random numbers and placed in closed containers.Sensory evaluation was carried out at 5 ○ C and relative humidity of 68 %.Hedonic rating (9-point scale; 1=dislike extremely, 9=like extremely) was used for rating flavour, colour and appearance, body and texture, sweetness and overall acceptability.Each panellist was given three replications for every sample and necessary training was imparted to avoid any biasing during the evaluation of the sample.

Statistical analysis
Response Surface Methodology (RSM) was used to optimise the various ingredients of rasmalai ball.A Central Composite Rotatable Design (CCRD) was used to design experiments consisting of three independent factors.The experimental data obtained from the design were analysed by the package Design-Expert® version 8.7.1 software, Stat-Ease, Inc., Minneapolis, MN, USA using the following second order polynomial equation: Yi = βo + "βi Xi + "βii Xi2 + "βijXiXj Where, Yi was the predicted response, βo was a constant, βi was the linear coefficient, βii was the ii th quadratic coefficient and βij was ij th interaction coefficient, and XiXj were independent variables.Kruskal Wallis test was used to determine the optimum concentration of sucralose in the sweetened concentrated milk based on the sensory scores.

Optimisation of ingredients in rasmalai ball
Using CCRD, levels of variables viz., tulasi extract, ashwagandha powder and isabgol were selected through 20 experiments (Table 1).The optimisation of the ingredients in the ball was carried out on the basis of sensory scores (Table 2).Table 3 displays the estimated quadratic polynomial model regression coefficients for the response variables together with the accompanying R 2 , adj-R 2 , Pred-R 2 , Coefficients of Variation (CV), and PRESS values.The limitations chosen for ingredient optimisation and the outcomes of optimised levels and estimated optimal response values using the desirability function are depicted in Tables 4 and 5, respectively.The effect of variables on sensory scores of fibre incorporated reduced calorie herbal rasmalai is presented below.

Flavour
The scores obtained for the sensory attribute, flavour of herbal rasmalai ranged from 6 to 7.7.The quadratic equation obtained by the Response Surface Application (RSA) of the data showing the effect of tulasi extract (A), ashwagandha root powder (B) and isabgol (C) could be presented as follows: F-Value of 43.91 was significant whereas lack of fit was found to be nonsignificant.Coefficient of determination (R 2 ) was found to be 97.5 per cent which showed 97.5 per cent variations in the response detailed by the variables in the model.Adequate precision ratio of 18.60 was obtained which indicates an adequate signal.The F-value for the flavour

Colour and appearance
The colour and appearance scores obtained for rasmalai varied from 7.8 to 6.6.The model showed a significant F-value of 17.66 whereas lack of fit was found to be nonsignificant.A coefficient of determination (R 2 ) of 94 percent was obtained which indicates 94 percent variations in the response were shown by the variables in the model.Adequate The F-value for colour and appearance was more than the tabled F-value at five per cent level of significance (p<0.05).The determination coefficient (R 2 ) of 0.94 with adequate precision of 13.61 clearly suggests the adoption of this response viz., colour and appearance to guide this design.The p value of the colour and appearance indicated that tulasi extract, ashwagandha root powder and isabgol had significant impact on the colour and appearance scores of herbal rasmalai.Factors A and C had positive effect on colour and appearance while the factor B affected scores negatively at quadratic levels.A similar trend 6.9 6.8 6.9 7 6.7 was also reported by Kumar et al. (2013) in the development of herbal ice cream by addition of tulasi extract.

Body and texture
The highest score for body and texture was 7.8 while lower score of 6.2.The model showed a significant F-value of 13.93 whereas lack of fit was found to be non-significant.A coefficient of determination (R 2 ) of 92.6 percent was obtained which indicated 92.6 per cent variations in the response were detailed by the variables in the model.Adequate precision ratio of 13.93 was obtained which indicates an adequate signal.The F-value for body and texture was more than the tabled F-value at five per cent level of significance (p<0.05).The coefficient of determination (R 2 ) of 0.92 with adequate precision of 13.51 firmly suggests the adoption of this response viz.body and texture to guide this design.Since the lack of fit test resulted in a non-significant F value, it was evident that the model is accurate enough for forecasting the body and texture of herbal rasmalai.The p-value of the body and texture model showed that factors ashwagandha root powder (B) and isabgol had a significant impact on body and texture whereas impact of tulasi extract (A) was non-significant at quadratic levels.All the three factors had a positive impact on the body and texture score of herbal rasmalai.Trivedi et al. (2014) and Indu and Awasthi (2018) reported observations contradictory to this.

Sweetness
The model showed a significant Fvalue of 12.01 whereas lack of fit was found to be non-significant.Coefficient of determination (R 2 ) was found to be 91.5 per cent which showed 91.5 per cent variations in the response detailed by the variables in the model.Highest score obtained for sweetness was 7.8 while the minimum score was 6.4.The effect of three factors on sweetness is showed in the table F-value for sweetness was more than the tabled F-value at five per cent level of significance (p< 0.05).The coefficient of determination (R 2 ) of 0.91 with adequate precision of 9.24 firmly suggests the use of this response viz.sweetness to guide the design.Since the lack of fit test resulted in a non-significant F value, it was clear that the model is authentic enough for forecasting the sweetness of herbal rasmalai.The p-value of the sweetness model showed that factors tulasi extract(A) and ashwagandha root powder (B) had non-significant (p>0.05)effect while isabgol (C) had a significant effect on the sweetness score of herbal rasmalai.At quadratic level, all the factors had a positive effect on the sweetness.Suryawanshiet al. (2020) in rasogolla and Kumar et al. (2013) in herbal ice cream observed effects contradictory to this.

Overall acceptability
The sensory scores obtained for overall acceptability ranged from 6.20 to 7.9.F-value of model was 22.19 whereas lack of fit was found to be non-significant.Coefficient of determination (R 2 ) of 95.The F-value for overall acceptability was more than the tabled F-value at five per cent level of significance (p< 0.05).The coefficient of determination (R 2 ) of 0.95 with adequate precision of 15.053 firmly suggests the use of this response viz.overall acceptability to guide the design.The p-value of the overall acceptability model indicated that all the three factors had significant (p<0.05)effect on the overall acceptability score of herbal rasmalai.The impact of all the factors viz., tulasi extracts (A), ashwagandha root powder (B) and isabgol (C) on the sensory score of overall acceptability was positive at quadratic levels.Husain and David (2018) observed similar trend on addition of tulasi extract and ashwagandha root powder whereas Suryawanshi et al. (2020) reported contradictory to this.Sweetened concentrated milk for the soaking of rasmalai balls was prepared by replacing the sugar completely with sucralose at different levels like T2 (100 ppm), T3 (200 ppm), T4 (300 ppm) and T5 (400ppm).The treatments were compared with control (5% sugar) and the obtained sensory scores were  The effect of varying levels of sucralose on the sensory characteristics of rasmalai is given in the Table 6.T2 (100 ppm) got maximum sensory scores for the entire sensory attribute except colour and appearance.It was also most similar to control with non-significant difference from T1 in terms of all the sensory attributes.Hence T2 was selected as the optimum level of sucralose for the sweetened concentrated milk in the development of fibre incorporated reduced calorie herbal rasmalai.

conclusion
RSM was used to estimate the optimal amounts of tulasi extract, ashwagandha root powder and isabgol for the production of herbal rasmalai balls and sweetened concentrated milk through Kruskal Wallis test based on sensory attributes.Out of 20 formulations for the optimisation of the ball, first formulation had the highest desirability (0.90) when compared to others.Hence, the rasmalai ball with 0.951 per cent tulasi extract, 0.423 per cent ashwagandha root powder and 0.583 per cent isabgol and sweetened concentrated milk with 100 ppm sucralose was selected for the formulation of fibre incorporated reduced calorie herbal rasmalai.The added herbs and reduced calorie may help to increase the product acceptability especially among healthconscious consumers.

acknowledgments
The authors gratefully acknowledge the laboratory support extended by Department of Dairy Technology, Verghese Kurien Institute of Dairy and Food Technology, Kerala Veterinary and Animal Sciences University, Mannuthy, Thrissur to carry out the study.

table 1 .
The

table 2 .
Sensory characteristics of rasmalai ball with different levels of tulasi extract, ashwagandha root powder and Isabgol

table 3 .
Estimated parameters of model for sensory attributes and responses of fibre incorporated herbal rasmalai balls with different levels of tulasi extract, ashwagandha root powder and Isabgol Figures are the Mean ± Standard error of six replications, *-significant at five per cent level (p<0.05),**-significant at one per cent level (p<0.01),ns-non-significant (p≥0.05)

table 4 .
Constraints and criteria for optimisation of Rasmalai ball with different levels of tulasi extract, ashwagandha root powder and isabgol

table 5 .
Solution obtained after response surface analysis

table 6 .
Effect of different levels of sucralose on sensory characteristics of sweetened concentrated milk