Use of Microbes In The Production Of Yoghurt
Title
To determine the effect of milk type and starter culture dose on the sensory and pH parameters
This research is aimed to develop understanding of the impact of milk type and starter culture dose on the sensory and pH parameters. From the analysis of the data set of 455 responses, it can be determined that milk type has a significant impact on the firmness value, sourness value and Graininess value, whereas starter culture dose has an influence on Graininess value.
Pasteurisation is used in the production of milk and milk-derived products to reduce the microbial contamination of foods for human consumption. There is a significant impact of temperature on the quality of the resultant food product. It causes variation in the optimal temperature and duration of pasteurisation for different products (Sameen et al., 2010). Therefore, it is required to assess the effect of milk type and starter culture dose on the sensory and pH parameters.
A dataset of 455 responses is developed through investigation of the effect of milk type (skimmed, semi-skimmed and whole) and starter culture dose (20units, 100units) on various sensory parameters and on pH. In order to analyze this data, regression analysis is used (Gnanadesikan, 2011).
Results in tables:
Table 1: Effect of milk type on the sensory and pH parameters
| SUMMARY OUTPUT | ||||||||
| Regression Statistics | ||||||||
| Multiple R | 0.516382137 | |||||||
| R Square | 0.266650511 | |||||||
| Adjusted R Square | 0.253525688 | |||||||
| Standard Error | 0.706217584 | |||||||
| Observations | 456 | |||||||
| ANOVA | ||||||||
| df | SS | MS | F | Significance F | ||||
| Regression | 8 | 81.06175535 | 10.1327194 | 20.31650329 | 2.96598E-26 | |||
| Residual | 447 | 222.9382447 | 0.49874328 | |||||
| Total | 455 | 304 | ||||||
| Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | Lower 95.0% | Upper 95.0% | |
| Intercept | -16.72612615 | 1.932102705 | -8.65695499 | 8.85926E-17 | -20.52325891 | -12.9289934 | -20.5232589 | -12.9289934 |
| Bitterness value | -0.000921276 | 0.001694865 | -0.54356923 | 0.587008917 | -0.004252169 | 0.00240962 | -0.00425217 | 0.00240962 |
| Firmness value | 0.005893417 | 0.001527533 | 3.8581266 | 0.000131069 | 0.002891379 | 0.00889546 | 0.00289138 | 0.00889546 |
| Flavour value | -0.000973397 | 0.001678598 | -0.57988684 | 0.562283095 | -0.00427232 | 0.00232553 | -0.00427232 | 0.00232553 |
| Graininess value | -0.005473669 | 0.001515541 | -3.61169228 | 0.000338694 | -0.008452139 | -0.0024952 | -0.00845214 | -0.0024952 |
| Off-taste value | -0.002082052 | 0.001737531 | -1.19828196 | 0.231442203 | -0.005496796 | 0.00133269 | -0.0054968 | 0.00133269 |
| Overall value | -0.000968738 | 0.002056635 | -0.47103061 | 0.637848662 | -0.005010613 | 0.00307314 | -0.00501061 | 0.00307314 |
| Sourness value | 0.004192819 | 0.002018002 | 2.07770744 | 0.038306564 | 0.000226868 | 0.00815877 | 0.00022687 | 0.00815877 |
| pH value | 4.856077578 | 0.49984905 | 9.71508814 | 2.27428E-20 | 3.873731661 | 5.8384235 | 3.87373166 | 5.8384235 |
Table 2: Effect of starter culture dose on the sensory and pH parameters
| SUMMARY OUTPUT | ||||||||
| Regression Statistics | ||||||||
| Multiple R | 0.73298151 | |||||||
| R Square | 0.537261894 | |||||||
| Adjusted R Square | 0.528980227 | |||||||
| Standard Error | 27.48250297 | |||||||
| Observations | 456 | |||||||
| ANOVA | ||||||||
| df | SS | MS | F | Significance F | ||||
| Regression | 8 | 391986.2777 | 48998.2847 | 64.87364647 | 4.77834E-70 | |||
| Residual | 447 | 337613.7223 | 755.287969 | |||||
| Total | 455 | 729600 | ||||||
| Coefficients | Standard Error | t Stat | P-value | Lower 95% | Upper 95% | Lower 95.0% | Upper 95.0% | |
| Intercept | 1647.770362 | 75.18790171 | 21.9153657 | 7.76715E-73 | 1500.004695 | 1795.53603 | 1500.00469 | 1795.53603 |
| Bitterness value | -0.03542268 | 0.065955775 | -0.53706715 | 0.591488457 | -0.165044585 | 0.09419923 | -0.16504458 | 0.09419923 |
| Firmness value | 0.443162799 | 0.059444063 | 7.455123 | 4.697E-13 | 0.326338265 | 0.55998733 | 0.32633827 | 0.55998733 |
| Flavour value | -0.100622091 | 0.065322738 | -1.54038386 | 0.124174394 | -0.228999898 | 0.02775572 | -0.2289999 | 0.02775572 |
| Graininess value | -0.131381293 | 0.058977386 | -2.22765542 | 0.026400533 | -0.247288675 | -0.01547391 | -0.24728867 | -0.01547391 |
| Off-taste value | 0.03055581 | 0.067616134 | 0.45190117 | 0.651559377 | -0.102329174 | 0.16344079 | -0.10232917 | 0.16344079 |
| Overall value | 0.060011873 | 0.080034095 | 0.74982885 | 0.453752246 | -0.097277945 | 0.21730169 | -0.09727794 | 0.21730169 |
| Sourness value | 0.064858681 | 0.078530696 | 0.82590228 | 0.409300111 | -0.08947653 | 0.21919389 | -0.08947653 | 0.21919389 |
| pH value | -417.1848453 | 19.4516581 | -21.4472639 | 1.10441E-70 | -455.4129002 | -378.95679 | -455.4129 | -378.95679 |
On the basis of the graph 1, 2 and 3, it can be determined that mean value of firmness, sourness and graininess differs with the milk type significantly. Firmness is the highest for whole milk, while lowest for skimmed milk. At the same time, sourness value is the highest for skimmed milk while it is the lowest for whole milk.
Apart from this, graininess value is the highest for skimmed milk whereas lowest for semi type milk. From the above table 1, it can be stated that firmness value, sourness value and Graininess value are statistically significant in perspective of milk type (p<0.05). It means milk type has a significant impact on these sensory and pH parameters (Chambers, 2018). On the other hand, the results are not significant for bitterness, flavor, off-taste, overall value and pH value in perspective of milk type.
Table 2 shows that the results are significant only for graininess value (p<0.05) in relation to starter culture dose, so it can be interpreted that starter culture dose has a significant impact on graininess value only (Frau et al., 2014).
Based on the above research, it can be summarized that there is a significant impact of milk type on firmness value, sourness value and Graininess value and starter culture dose has an impact on Graininess value.
References
Chambers, J.M., 2018. Graphical methods for data analysis. CRC Press.
Frau, F., Font de Valdez, G. and Pece, N., 2014. Effect of pasteurization temperature, starter culture, and incubation temperature on the physicochemical properties, yield, rheology, and sensory characteristics of spreadable goat cheese. Journal of Food Processing, 2014.
Gnanadesikan, R., 2011. Methods for statistical data analysis of multivariate observations (Vol. 321). John Wiley & Sons.
Sameen, A., Anjum, F.M., Huma, N. and Nawaz, H., 2010. Chemical composition and sensory evaluation of mozzarella cheese: influence by milk sources, fat levels, starter cultures and ripening period. Pak. J. Agri. Sci, 47(1), pp.26-31.
