MATERIALS AND METHODS

Cross bred cow milk samples were procured form Banaras Hindu University Dairy farm, Varanasi and the freeze dried pure culture of Streptococcus salivarius subsp. thermophilus and Lactobacillus delbruechii subsp. bulgaricus were procured from the National Dairy Research Institute, Karnal, Haryana (India). The S. thermophilus and L. bulgaricus were mixed in the ratio of 3:1 (volume basis) in the culture.

The fresh cow milk was standardized for 4% fat and 14% SNF (Solid- not fat) using fresh cow cream and skim milk powder (M₁) and fresh cow cream along with admixture of skim milk powder (SMP) and sago powder in the ratio of 75:25 (M₂). Two levels of sugar 4% (S₁) and 6% (S₂) and three levels of carrot juice 0% (C₀), 2% (C₁) and 5% (C₂) were added in milk samples M₁ and M₂. The yoghurt prepared with all the levels of sugar and carrot juice from milk M₁ was designated as group-I and from milk M₂ as group-II. All the samples were heated at 90°C for 10 min and cooled at inoculation temperature (41±0.5°C). The samples were inoculated at 41±0.5°C using 1% mixed starter culture for 8 h. Evaluate the physical attributes of the product, score card for fermented milk product as suggested by Nelson and Trout (1981) was followed. Each sample was judged by a panel of five experienced judges and scored for different qualitative parameters (flavour, body and texture, colour and appearance, acidity) of the product.

Statistical analysis: The experiment was laid out in factorial randomised block design. The experiment data was analysed using the methods of Snedecor and Cochran (1994).

RESULTS AND DISCUSSION

The yoghurt samples prepared under various treatments were analysed for important and major physical attributes as fallow:

Flavour: The highest flavour score (33.94) was found in the yoghurt sample M₁S₂ while the samples prepared M₂S₁ scored lowest value (32.17). The difference in the interaction effect between milk and sugar groups of flavour score (Table 1) was not significant. The highest flavour score (34.75) was recorded in the sample M₁C₁ whereas, the lowest flavour score was recorded in the yoghurt samples S₂C₀. The flavour score of yoghurt samples increased (p<0.01) with the addition of 6% sugar and 2% carrot juice (34.50), over samples prepare by 4% sugar without carrot juice (31.58).

The maximum flavour score (35.00) in yoghurt was recorded in the sample M₁S₂C₁. The value was comparatively lower when the yoghurt samples M₂S₁C₀ (Table 2). The highest flavour score was found in the samples prepared from 2% carrot juice with 4% and 6% sugar in both the levels (0, 5%) of carrot juice. The best flavor score have also been reported by Aly et al. (2004) when yoghurt was prepared with 5% carrot juice as compared to the yoghurt prepared with 0, 10, 15 and 20% levels of carrot juice. Patil et al. (2009) reported maximum flavour score at 5% guava pulp and 9% sugar, over the yoghurt the prepared with 15% guava pulp and 6% sugar. They have also noted that as the levels of guava increased (from 5%) in the samples and sugar decreased (from 9%) the flavor score of yoghurt decreased (p>0.05).

Table 1:	Physical attributes of carrot yoghurt and their interactions between milk with sugar, milk with carrot juice and sugar with carrot juice

Table 2:	Physical attributes of carrot yoghurt and their interaction with milk, sugar and carrot juice

Body and texture: The difference in the interaction effect between milk and sugar on the body and texture score of yoghurt was significant (p<0.05). The higher body and texture score (23.17) was found in the yoghurt sample M₁S₂ while the sample M₂S₁ scored lowest value (21.28). The highest body and texture (24.50) score was recorded in the samples M₁C₁ whereas, the lowest score was recorded in the samples M₂C₂ (Table 1). The body and texture score (23.58) of yoghurt samples increased (p<0.01) with the S₂C₀. The lower body and texture score was recorded in the samples S₁C₂.

The highest body and texture scores (24.67) was recorded when samples M₁S₂C₁ comparatively lower (19.50) values were recorded in the samples M₂S₁C₂. Prior research had observed that panel prefer yoghurt samples were lowered body and texture (Aly et al., 2004; Kale et al., 2007; Ghadge et al., 2008) due to increased level of carrot juice, pomegranate, honey and apple. Vahedi et al. (2008) and Walkunde et al. (2009) had also contrary findings when used milk and sugar decreased body and texture score in the yoghurt samples.

Colour and appearance: Colour and appearance score (11.22) was the highest in M₁S₂ whereas, the yoghurt prepared from SMP+sago powder based milk mixed with 4% sugar (M₂S₁) scored lowest value (10.06). The interaction effect between milk and sugar scores in the samples (Table 1) was found to be very high (p<0.01). Among the interaction effect between milk and carrot juice, the yoghurt samples M₁C₁ showed highest value (12.17) whereas, the samples M₂C₀ showed lowest score (9.17). The interaction effect in the values obtained between sugar and carrot juice was found to be very high (p<0.01). The highest colour and appearance score was in the sample S₁C₁ (12.08) while the score was very low in the sample S₂C₀ (9.00).

The score (12.67) was significantly very high (p<0.01) in the samples prepare from SMP based milk blended with 6% sugar containing 2% carrot juice (M₁S₂C₁). These results were in close agreement by the observation of Guven and Karaca (2002), Aly et al. (2004), Lovely and Meullenet (2009), Patel et al. (2009) and Walkunde et al. (2009).

Acidity score: A critical observation of the data presented in Table 1 indicates clearly that the interaction effect between milk and sugar had no significant impact on acidity score of yoghurt. The highest acidity score (6.30) was found in the yoghurt samples M₂C₀ while the yoghurt sample M₂C₂ scored lowest acidity score (4.90). The interaction effect between sugar and carrot juice was significantly (p<0.01) higher in yoghurt prepared from 6% sugar along without carrot juice (S₂C₀) than the lowest acidity score recorded in group S₂C₂ (5.07).

The increased (p<0.01) acidity score due to with the interaction between milk, sugar and carrot juice (Table 2). The interaction effect values between SMP based milk, 6% sugar and without carrot juice (M₁S₂C₀) was the highest (6.60). The lowest acidity score (4.83) was found in the sample M₂S₁C₂. The interaction of SMP, sago powder, sugar and carrot juice these ingredients increased in the samples. Therefore, acidity score was decrease. The present findings are at par with the findings reported by Drake et al. (2001), Kale et al. (2007) and Patel et al. (2009).

CONCLUSION

Therefore, it can be concluded that the body and texture and acidity score decreased significantly (p<0.01) in the carrot yoghurt samples while the carrot juice was increased levels of 0, 2 and 5% in all yoghurt samples. The flavour and colour and appearance scores were significantly (p<0.01) higher in the samples prepared with 2% carrot juice as compared to yoghurt prepared with 0 and 5% levels of carrot juice in all the groups.