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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

Abstract

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.

Introduction

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.

Method

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 R0.516382137
R Square0.266650511
Adjusted R Square0.253525688
Standard Error0.706217584
Observations456
ANOVA
 dfSSMSFSignificance F
Regression881.0617553510.132719420.316503292.96598E-26
Residual447222.93824470.49874328
Total455304
 CoefficientsStandard Errort StatP-valueLower 95%Upper 95%Lower 95.0%Upper 95.0%
Intercept-16.726126151.932102705-8.656954998.85926E-17-20.52325891-12.9289934-20.5232589-12.9289934
Bitterness value-0.0009212760.001694865-0.543569230.587008917-0.0042521690.00240962-0.004252170.00240962
Firmness value0.0058934170.0015275333.85812660.0001310690.0028913790.008895460.002891380.00889546
Flavour value-0.0009733970.001678598-0.579886840.562283095-0.004272320.00232553-0.004272320.00232553
Graininess value-0.0054736690.001515541-3.611692280.000338694-0.008452139-0.0024952-0.00845214-0.0024952
Off-taste value-0.0020820520.001737531-1.198281960.231442203-0.0054967960.00133269-0.00549680.00133269
Overall value-0.0009687380.002056635-0.471030610.637848662-0.0050106130.00307314-0.005010610.00307314
Sourness value0.0041928190.0020180022.077707440.0383065640.0002268680.008158770.000226870.00815877
pH value4.8560775780.499849059.715088142.27428E-203.8737316615.83842353.873731665.8384235

Table 2: Effect of starter culture dose on the sensory and pH parameters

SUMMARY OUTPUT
Regression Statistics
Multiple R0.73298151
R Square0.537261894
Adjusted R Square0.528980227
Standard Error27.48250297
Observations456
ANOVA
 dfSSMSFSignificance F
Regression8391986.277748998.284764.873646474.77834E-70
Residual447337613.7223755.287969
Total455729600
 CoefficientsStandard Errort StatP-valueLower 95%Upper 95%Lower 95.0%Upper 95.0%
Intercept1647.77036275.1879017121.91536577.76715E-731500.0046951795.536031500.004691795.53603
Bitterness value-0.035422680.065955775-0.537067150.591488457-0.1650445850.09419923-0.165044580.09419923
Firmness value0.4431627990.0594440637.4551234.697E-130.3263382650.559987330.326338270.55998733
Flavour value-0.1006220910.065322738-1.540383860.124174394-0.2289998980.02775572-0.22899990.02775572
Graininess value-0.1313812930.058977386-2.227655420.026400533-0.247288675-0.01547391-0.24728867-0.01547391
Off-taste value0.030555810.0676161340.451901170.651559377-0.1023291740.16344079-0.102329170.16344079
Overall value0.0600118730.0800340950.749828850.453752246-0.0972779450.21730169-0.097277940.21730169
Sourness value0.0648586810.0785306960.825902280.409300111-0.089476530.21919389-0.089476530.21919389
pH value-417.184845319.4516581-21.44726391.10441E-70-455.4129002-378.95679-455.4129-378.95679

Discussion

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).

Conclusion

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.

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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 Processing2014.

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. Sci47(1), pp.26-31.

 

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