J. Daiying, Foods & H.S. 25 (3/4) : 190-193.2006

MICROBIAL ASSAY AND SHELF LIFE ANALYSIS OF VARIOUSBRANDS OF PACKED MILK AVAILABLE IN AND AROUND MADURAI

Thahira Banu. A, P GeethaDepartment of Food Service Management and Ditetitics, The Thassim Beevi Abdul Kader

College For Women, Kilakarai.

ABSTRACTSix brands of pasteurized milk packs were collected, which had a high market turnover In and

around Madura!. The nutrients like protein, fat, lactose, calcium, total solids, solids non fat, microbial/1000, keeping quality and effectiveness ofpasteurization were ana\yzed using standardized procedures.Curd was prepared out of the selected brands of milk and tested for organoleptic changes and shelflife for a period of 72 hours. From the study it was found that the nutrient composition of Arokyabrand was within the standard limits with fat 3.65%,protein3.47%,lactose 4.9%.All the samples hadsolid non fat and total solids with standard limits of 8.55 to 10.5% and 11.4% to 14% respectively.Bacterial count was also within standard microblal'limlts of 1000 -10,000 microbes per ml, Arokya,SNp, Vijay had very good keeping quality with <4000 mlcrobes/ml and took longer time for dyedecolorisatlon Indicating its keeping quality to be very good. All the brands of selected milk hadundergone effective pasteurization techniques, since they all showed negative In the presence ofphosphates test. The shelf life and organoleptic changes of curd prepared were tested for 72 hoursand it was found that the acidity of l"and 2'" day curds were within the standard limits of 0.65% to0.85% and yeast and mould count ranged &om 3Q-85/mI.The mean overall acceptability score was6.9 for curd prepared out of Arokya milk ,which had higher acceptability score than any other brandselected. Thus the study reveals that in terms of nutrient composition, keeping quality and productacceptability of Arokya was better than any other brand.

A total of ten different brands of milkwere identified by means of a questionnaire.

out of these six brands of milk, which had ahigh market turnover were selected as thesamples for study. The selected samples wereAavin, Amirtha, Arokya, Komatha, SNP andVijay. The selected milk samples were analyzedfor their nutrient composition fat (Gibermethod,1977), protein (Lowry eta1.,1951),lactose(AOAC,1997) andcalcium(Hawketal.,1957).TotaIsolldsand total non fat solids (AOAC, 1997),totalbacterial count (Istawankiss, 1984). Keepingquality of milk was tested using Methylene BlueReeducates Test and Clot on Boiling Test. Theresults were compared with standards given byFAO, 1964. Effectiveness of pasteurization wastested by Phosphates Test.

Curd being one of the commonly preparedand used fermented milk products in Indianhomes, curd was prepared out of the selected

'~ .milk samples. The milk was boiled at 75degree. centigrade for 5-10 minutes and cooled to room

temperature and inoculated with 0.5-1.1 %starter and allowed to set at room temperature.

INTRODUCTION

India has emerged as the largestproducer of milk in the world with a record ofabout 78 million tones since 1998.(DairyIndia,1997).Currently about 46% of the milkproduction is consumed as milk and 54% isutilized for conversion in to other milk productsand 7.8% is used for production ofcurd.(Clarence and Henry, 2001)The presentday market has different brands of milk andmilk products including fortified, enriched andadulterat€d items. So it is important for th~

consumers to understand the quality of milkthey purchase and consume. Thus the presentstudy was planned to estimate the nutrient andmicrobial quality ofselected brands of milk andorganoleptic changes and shelf life of curdprepared out of the selected milk samplesduring the year 2000.

MATERIAL AND METHODS

BRAND NAME

Aavin IAmirthallArokya IIIKomatha IVSNPVVijayVl

Vol. 25. No. 3/4. 2006

TABLE 1 : Nutrient composition of the selected packed milk

Fat (g)% Protein (g)% Lactose %

3 3.2 4.663 3.32 4.874.5. 3.74 4.93.2 3.44 4.93.5 3.29 4.83.7 3.7 4.9

TABLE 2 Total solids & total non fat solids of selected milk samples.

191

Calcium(mg)%

145160162187170167

BRAND NAME

AiivinAmirthaArokyaKomathaSNPVijay

Solids non fat (SNF%) •Total solids (TS%)

8.5 12.59.0 12.08.5 13.149.5 13.19.0 12.59.0 12.2

The prepared curd was tested for shelf life andorganoleptic changes for a period of 72 hours.The acidity (BIS,1973) method was used to testacidity .Organoleptic changes were evaluatedusing a 9 point hedonic scale, the scores were givenfor different parameters like appearance,color .taste,texture and flavor and the overall acceptabilityscore was calculated. Shelf life was tested byestimating the yeast and mould counts.

RESULTS AND DISCUSSION

From the survey, it was found that 45%of the selected shops sold Arokya milk and 40%Aavin, 20-35% of the shops sold other brandsof milk like SNp, Vijay, Amirtha, Asai, Raj,Akshya, Komatha and Seva. Though so manybrands of milk were available, the investigatorselected only these six brands of milk, sincethey had higher sales than other brands.

The nutrient composition of theselected packed milk is given in Table I. Thepercentage of fat, protein and lactose was highin Arokya with 4.5per cent, 3.47 per cent and4.95 per cent respectively. The difference innutrient content may be due to the breed ofthe cow. Nutrient content of Jersey andAryshirne are, fat 3.7g and5.1g per cent, protein3.4% and 3.8 per cEmt and lactose 4.8 and 5.0percent respectively. (Robinson, 1990)

Calcium was found to be high inKomatha brand with 187mg of calcium. Thismay be due to collection of milk from varioussocieties including buffalo milk. Calciumcontent of cow's milk and buffalo's milk are120mg and 210mg respectively.(Gopalanetal,1991).

All the selected samples had solid nonfat percent and total solids within the standardlimits of solid non-fat of 8.5-10.5 percent andtotal solids 11.4 to 14 percent.(Shakuntalamanay, 1997). The total solids and total nonfat solids of the selected milk samples are givenin Table 2

The total bacterial count of the selectedmilk sample is given in Table 3. All the selectedmilk samples had microbial load within thestandard limit of pasteurized milk, 1000 to10,000 microbeslml.(Frazier,1997)

In order to understand the keepingquality of milk, the selected samples weresubjected to Methylene Blue Reductase Testand Clot on Boiling Test.

The longer the time taken fordecolorization, the lesser the number ofmicroorganisms. Thus from the results Arokya,SNP and Vijay brands of milk had taken 5and 5 1/2 hours compared to the other brandswhich had taken 4 and 4 1/2 hours, indicating

192 J. DAIRYING, FOODS & H.S.

TABLE 3 : Total bacterial count of the selected milk samples

BRAND NAME No. of M.O/mt

Aavin 4500Amirtha 4000Arokya 3000Komatha 5000SNP 3500\fIjay 3500

TABLE 4 : Standards for methylene blue reductase test

Time taken for dye decolorisationMore than 7 hours5 to 7 hours3 to4 hours1 to 2 hoursBelow 1/2 hour

ReportExcellentV.GoodGoodFairPoor

TABLE 5 : Standards for clot on boiling

No.of M.O/m_' _<3000< 4000>5000ooסס1<

> ooסס3

Clot on boilin.9. time8hrs and above5to7hrs4to5hrs3to4hrs2 hrs and below

GradeExcellentV.GoodGoodFairPoor

The effectiveness of pasteurization ofthe selected brands was tested usingPhosphatase test. All the samples had alkalinePhophatase activity < 4JLg of standard phenolper ml, indicating the absence of phosphatase.This indicates proper pasteurization techniquesfollowed by the manufacturers.

In order to test the shelf life of milkproducts selected out of selected brands, curdwas selected, due to the wide and commonuse in Indian cookery and diet.

The organoleptic changes of curd werestudied for a period of 72 hours. The mean

the keeping quality of Arokya, SNP and Vijay overall acceptability of the prepared curd outwere better and rated very good of all the other of Arokya milk had a highest score of 6.9, thanselected brands. The result was compared with the other brandsthe FAOstandards 1964, given in Table 5., The acidity of the fresh, first and

From the test it was found that Arokya second day cu~d ranged between 0.51-0.6?l?erd S rdl' h . cent. Accordmg to BIS, 1973 the aCidIty

an . NPtook8hr::forcu mg,~ ereasAavm, requirement should not exceed 0.7%. TheAmlrtha and VIJay took 7 Y2 hours an? acidity levels in the samples were within theKomatha took 7 hrs. Thus from the result It limits but the levels increased to 1.4 to 3% inwas clear that keeping quality of Arokya and the third day curd, making it unpalatable.SNP were excellent and others graded as verygood. The yeast and mould count of the fresh

to two days old curd ranged between 30 and85 per ml which was within the standard limitsof not exceeding 100. (FAO, 1993). The thirdday curd it was above 100, indicating that wasnot acceptable for consumption.

CONCLUSION

It was concluded in the present study,that, among the selected brands, the nutritionalcomposition, keeping quality of Arokya milkand shelf life, organoleptic changes of theprepared curd out of Arokya milk were betterthan the other selected brands. It is necessaryto provide information about the differentqualities of packed milk sold in the market.

Vol. 25, No. 3/4, 2006

REFERENCES

19'3

AOAC, (1997), Official Methods of Analysis of the Association of Official Analytical Chemist, 16th edn, Washington DCBIS (1973) Specification for Fermented Milk Products IS: 7035,Bureau of Indian Standards, NewDelhi.Clarence, A and Henry, D. (2001) in : Milk and Milk products,3'd edn. : 180-190.Dairy India (1997) Annual Report, Journal of Dairying Foods and Home Science, vol. 24, No.1,2oo5 :35FAO,(1964), Report on Rules and Expert Consultation of Quality of Food ProductsFAO (1993) Report on Rules and Expert Consultation of Quality of Food Products.Frazier CW and Dennis C Westhoff (1997) Methods of Microbiology Processing Techniques used in Dairy Industry,

Food Microbiology, Tata Mcgraw Hill Publishing Company Ltd, NewDelhi:509Geber (1977) IS: 1224, Determination of fat by Geber's methods, part -1. Milk, Indian Standard Institution. New Delhi.Gopalan et ai,(1991) Nutritive Value of Indian Foods,NIN,ICMR,Hyderabad-94.Hawk, Oser and Summerson(1957) Practical Physiological Chemistry 13th ed.: 644.lstawankiss, (1984), Testing Methods of Food Microbiology: Elsevier Pub, pp.395-397Lowry OH, et al (1951) Indian Journal. Vet.Sci.Anim, Husbandary,22: 13-25.Robinson, D(1990),Dairy Microbiology,2 001,2 edn, Elsevier Applied Science Publishers, London,: 301and 409.ShankuntaIa, Manay(2oo1) Standards for Milk Nutrients, Food facts and Principles,2nd edn, New Age International (P)

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