Dr. Aprna Sharma and Dr. S. Karthikeyan, Department of Dairy Technology,
College of Dairy Science and Food Technology, Raipur, Chhattisgarh, India

Introduction
India is the largest and one of the most economical milk producers in the world, with an average production of 221.06 Million tonnes per annum (NDDB, 2021-22); Nearly 56 percent of total milk produced in India is utilized for preparation of variety of traditional milk products i.e., Khoa, Dahi, Basundi, Paneer, Chhana etc. Among these ‘Burfi’ is one of the most popular Khoa based sweets all over India. Burfi's rich flavour and palatability led to the development of several variations with different ingredients and flavours, such as orange, mango, coconut, etc. Thus, the purpose of incorporating "date seeds" (Phoenix dactylifera L.) powder is to take advantage of the high nutritional content and significant waste of the date industry. Therefore, a study was undertaken to optimise the Date Seed Powder (DSP) incorporated burfi and to evaluate its shelf life at room and refrigerated temperature.

Preliminary trials
In first phase, study was undertaken to screen the most suitable levels of Date Seed Powder (DSP) and milk fat content for burfi preparation. Two levels of fat contents viz., 4.5(F1) and 3.5 (F2) per cent were utilized as the base material for preparing khoa. For the screening of different levels of DSP viz., 1(D1), 2(D2), 3(D3) and 4(D4) per cent were used. The prepared burfi samples were subjected to sensory analysis using a 9 point Hedonic scale. Sensory evaluation revealed that the treatment (D1F1-1 per cent Date Seed Powder + 4.5 per cent milk fat) gave the superior color and appearance (8.27), body and texture (8.53) and flavor (8.04) scores and D4F2resulted in lowest score of color and appearance (5.74), body and texture (5.71) and flavor (5.65). The investigation revealed that treatments with DSP levels ranging from 1 to 4 per cent, combined with 3.5 per cent milk fat and a 4 per cent DSP level, garnered the lowest scores across all sensory attributes. As a result, these treatments were rejected due to their bitter taste and dry appearance in the final product. Consequently, DSP levels of 1, 2, and 3 per cent, along with 4.5 per cent fat milk containing treatment combination were selected for further study.

The second phase of the study involved screen optimum level of Carboxymethyl Cellulose (CMC) and0.5 (C1) 1 (C2) and 1.5 (C3) per cent were tried to address the issue of dryness caused by Date Seed Powder (DSP) and also as a partial fat replacer in preparation of burfi. All prepared burfi samples were subjected to sensory evaluation. The D1F1C2 (1 per cent Date Seed Powder + 4.5 per cent milk fat + 1.0 per cent CMC) secured the highest overall acceptability score (7.53), whereas, burfi made with CMC levels 0.5 (D1F1C1 - 1 per cent Date Seed Powder+ 4.5percent milk fat +0.5percent CMC) and 1.5(D1F1C3 - 1percent Date Seed Powder + 4.5 per cent milk fat + 1.5 per cent CMC) per cent scored the lowest in overall acceptability, 7.32and7.21 respectively. Sensory evaluation results showed that both lower (0.5) and higher (1.5) per cent CMC additions did not yield a satisfactory product.

In the third phase, two sugar levels 28 (S1) and 30 (S2) per cent were utilized along with screened DSP and CMC for burfi preparation. The incorporation level of sugar (28 per cent) in the prepared burfi showed a significant (P<0.05) impact on the overall acceptability The sensory evaluation results revealed that the treatment prepared with 28 per cent sugar (D1F1C2S1 - 1 per cent DSP+4.5percent milk fat +1percent CMC+28percent sugar) scored the highest overall acceptability (8.36) than other treatments. Hence, this rate of sugar addition was taken considered for further study.

In the fourth phase, the optimised DSP levels (1, 2 and 3 per cent), fat level in milk (4.5 per cent), 1 percent Sodium Carboxymethyl Cellulose (CMC) along with sugar (28per cent) and 0.5 per cent cocoa powder was used to prepare burfi and one control T0 and an experimental sample were designated as, T1, T2and T3. The fresh prepared burfi samples were subjected to physical (pH), chemical (moisture, fat, protein, ash, total carbohydrates, reducing sugar, dietary fibre and acidity) and sensory (colour and appearance, body and texture, flavour and overall acceptability) analysis and microbial (Standard plate count, yeast and mold and coliform count) quality. The prepared burfi samples were subjected to sensory quality using a 9 point hedonic scale. It was found that due to the incorporation of DSP all the chemical constituents (except moisture) of experimental samples were found to be significantly (P<0.05) different from control sample. Among all the fresh samples in terms of protein, total carbohydrate and reducing sugar, control (T0) had the lowest value of 13.27, 49.15 and 14.97 per cent while T3had the highest value of 14.49, 51.44 and 15.11 per cent respectively. However the dietary fibre content was not detected in sample control (T0) while sample T3had highest value i.e., 22.43g/100g. The fat and ash percent were highest in sample control (T0) and found to be 22.16 and 1.20 while T3 had the lowest per cent of 18.71 and 1.18 respectively. The average antioxidant activity of the final product was found to be 68.81, 72.28 and 76.24 per cent for treatments T1, T2 and T3 respectively. The sensory attributes color and appearance, body and texture, flavor and overall acceptability of all fresh samples were found to be significant (P<0.05).The fresh DSP incorporated burfi sample T1 (1% DSP+4.5%milk fat+1% CMC+28% sugar+0.5% cocoa powder) was more acceptable and secured highest scores for color and appearance (7.95), body and texture (8.28), flavor (8.05) and overall acceptability score (8.07). During the microbiological analysis of Standard plate count control (T0) sample achieved the lowest count 1.57 log10cfu/g while, the treatment sample (T3) exhibited the highest SPC count, at 1.68 log10cfu/g. In fresh burfi samples, yeast and mold counts were highest in T3 (1.02) followed by T2 (0.92), T1 (0.81) and T0 (0.73) log10cfu/g respectively. Although, the coliform count was absent on the day of production.

In the fifth phase, the chemical analysis of stored burfi samples at room (30±2°C) for 6 days and refrigeration temperature (7±2˚C) for 9 days was carried out for moisture, acidity and pH content. During room temperature storage, moisture and pH contents significantly decreased. Meanwhile, acidity content (%LA) showed a significant (P<0.05) increase, starting from 0.30 to 0.35 on 0th day and further increasing to 0.37to 0.41 on 6th day of storage for treatments T0 to T3. The SPC and YMC values of burfi samples at 6thdaywere 3.10 and 2.28 log10cfu/g respectively. At refrigerated storage temperature, it was ranges from 1.57 to 3.11 and 0.73 to 2.84 log10cfu/g for SPC and YMC on 9th day of storage respectively. Coliform count found to be nil at both room (30±2ºC) temperature and refrigerated (7±2ºC) temperature conditions. Sensory scores of most acceptable sample (T1) burfi sample which stored at room temperature in terms of colour and appearance, body and texture, flavor and overall acceptability were observed in the range of 7.95-6.35,8.28-6.05,8.05-6.22 and8.07-6.89 for 0to6 days and at refrigerated temperature for 0to9days, it was 7.95-6.21,8.28-6.05, 8.05-6.22 and 8.07-6.75 respectively.

The production costs per kg of control and DSP incorporated burfi samples were calculated and recorded to be Rs. 205.90 (T0), Rs. 221.30 (T1), Rs. 220.05 (T2) and Rs. 218.52 (T3). The highest cost obtained for the treatment T3 (218.52 Rs.). It was noticed that cost of product increased from Rs. 205.90 to Rs. 218.52 with increase in the incorporation of Date Seed Powder.

T0

0% DSP + 6 % fat + 28 % sugar + 0.5% cocoa powder

T2

       1% DSP + 4.5% milk fat + 1% CMC + 28 % sugar + 0.5% cocoa powder

T3

       2% DSP + 4.5% milk fat + 1% CMC + 28 % sugar + 0.5% cocoa powder

T4

3% DSP  +  4.5% milk fat +  1% CMC +  28 % sugar + 0.5% cocoa powder

Conclusion
The present study resulted that in the development of DSP incorporated burfi of acceptable quality with 6 and 9 days shelf life for room and refrigeration temperature storage respectively without any preservatives. Though the DSP incorporated burfi (T0) containing 4.5 per cent milk fat, 1 per cent DSP, 1 per cent Sodium Carboxymethyl Cellulose (CMC) along with 28 per cent sugar and 0.5 per cent cocoa powder resulted in most acceptable treatment combination among all treatment. This formulation could be used to prepare burfi without adversely affecting the chemical, sensory microbial quality. More importantly, all the burfi samples met the Bureau of Indian Standards (BIS) requirements.