Prof. Dr. Lcitif BERKMEN
T~E STUDY OF FAT CONTENT OF TURKISH YOCURT (*)
A.Cemal OMURTAG Dr., Specialist of
Barleriology and Contagi-Ous Diseases, Vet. Med.
E. Hayrünnisa OMURTAG Chemical Engineer ( •• )
HİSTORY OF YOGURT
Down through the centuries the Asiatic Turks have fermented
milk so that it would keep longer in a hot climate than wpuld. the
fresh product. This procedure has been and is now, very important
in areas of the world where rapid transportation' and refrigeration
are not generally available.
Yo~rt is but onı of the fermented milk products. Others inclu
de Kefir, Kımız, Araka, Tarho, Katıh, Punch of cheese, Punch of milk,
Dehri, Huslanka, Saur milk, Skyr, Wein of Galacton, Yazma,
Urgut-nik, Zioddu, Lebeniraib, Mazun. Kellermilch, Tatmjolk and Sostej.
The word «Yogurt» is of Turkish origin. it was in use nearly one
thousand years ago (11), (29)
According to AYGÜN (1) yo~ut is a Turkish discovery. it is a na-tional food that has bep-n usp-d for centııries in all Turkish countries ..
it was introduced into the Balkan countries by the Anadolu (Asia
Mi-nor) Turks. it was iı:ıtroduced into other European countries from the
Balkan countries about the begining of the twentieth century. YÖNEY
( 28) states yo~urt has been produced in the United states of America
for ~bOl't ty'p-nty-five years. But ROGERS (21) shows it has been pro-duced in the United St::ıtes since 1916.
(*) Presented at the VII. ıh Turkish Congress of Microbiology, September 18-21 )958, İstanbul. TURKEY
Types of Yoğurt and Methods of Production
There are three kin ds of yogurt: namely,
ı -
Yoğurt or silivri yoğurt.2 - Süzme Yoğurt or Torba Yoğurt (YQğurt of the eloth bagi.
3 - Kurut (çlried yoğurt) (1), (9).
ı.
Silivri YoğurtThis is one of the well-known yoğurts whieh is widely use d in th~
big cities. !ts produetion is a big industry. Milk from sheep,
eat-le, goats, and water buffaloes can be used for its produetion.
Tpe best yoğurt is made from sheep's milk. The first step in yo
ğurt produetion is boiling the milk with frequent stirring. This
stimu-lates evaporation. Speeial types of clean plates or bowls are filled
with known amounts of the boÜed milk. This is then allawed to eoo
to about 43-44°C. At this temperature the fat rises to the top and co
vers the milk. Eaeh plate or bowl is then inoeulated with two per cent of fis volınne of one-day"'Üld.yoğurt. This is diluted with equal parts
of water that has been boiled and allawed to cool to about 42-430 C. if
nonhon1ogenized milk is used. inoeulations are made with a syrin,se
so as not to disturb the fat layer. The inoeula~d milk is ineubated
at 37-40°C. until it has almost solidified.
RUDANOVSKAYA (23) reeommends the use of starter eultures
in tabı et from for the home preparation of yoğurt.
SOULtD (25) found yoğurt eultures remain viable for five to eight
months in milk.
RETCREL (20) suggested that a
pH:
meter fitted outside thein-cubator be used to determine when yoğurt has reaehed the proper aci-dity.
PETTE and LOLKEMA (5) stated the true yoğurt arama is
lin-ked with the produetion of aeetaldehyde.
2. Süzme (drained) Yoğurt
Süzme yoğurt mav be made from either Billvri yo~rt or from
the by-produet obtained when butter is made from yoğurto In either
ease, the eurd is hung in a cloth bag unti1 all the liquid that will drain out has eseaped. if made from silivri yoğurt, it eontains all the fat in the original milk when it is made from milk. witti a high fat eontent, the fat of the finished silivri yoğurt mav be removed and then added
n top of the yog-urt after it has been drained in a cloth bag. if made rom the by-product obtained after making butter, it is very low in fat
ontent'but contains the other constituents of milk. it is a palatable
nd nutritious food which is called Ayran.
Süzme yog-urt will keep about a week without refrigeration if it is roperly salted. if it is to be kept longer it is usually pressed, rolled
in-o egg shaped masses, put in a jar in-or in-other container, and covered
ith olive oil.
3. Kurut (Dried Yoğurt )
This type' of yog-urt is made from Süzme or Torba yog-urt by ad-ding salt, shaping it properly, and drying it in the sun. Kurut has been
ade and eaten in Turkey for many years. lt is mentioned in some ot
the old Turkish testaments.
İZMEN (9) found the content of Silivri yog-urt to be as follows Moisture
Dry solids Fat
Non-fat dry solids Totol Nitrogen Laetose Ash 83.630 % 16.370 % 4.930 % 1
ı.
437 % 6.451 % 4.103 % 0.976. %According to GÜLMEZOGLU and FİşEK (5) riboflavin, nicotinic
acid and biotin contents of 100 grams of yog-urt are 177,
ı.
2, and 186gammas, respectively.
The Proııerties of Yoğıırt
This is a relative1y stab1e milk produet. lts acidity inhibits the
aetivity of lipase (28) and of many baeteria. Rancidity develops only
slowly or not all. lts stability makes it especially valuable in hot co-o
."
untries with inadequate cooling equipment. .'
The digestibility of yog-urt is very high partly because
micro-orga-nisms have broken some' of' the complex components into simpler
substances (3).
HONDA (9) studied the mieroflora of yoğurt. He inoculated the
sour milk with some of the comman pathogenie bacteria to observe its bacteriostatic and bactericidal properties.
milk products containing viable M. tuberculosis, Bruceıla species, foo and mouth disease virus, or S. tyhi.
GOLEM (4) in 1944 stup.ied the survival time of S. typhi in Ayran
which is diluted yogurt. He found its bacteticidal action .was correlate with its pH.
The antibiotic, bactericidal, and protozoacidal properties and la,c-tic acid content of both cow's and hUlnan miIk were studied by SENE-CA, HENDERSON, and COLLİNS in 1950 (24). They found yogurt
pos-seseses both bacteriostatic and bactericidal properties against a wide
range of pathogenic and non-pathogenic bacteria and protozoa. They
state the se properties are directly related to the lactic acid content o the yogurt. They also found the antibiotic factor in yogurt is diffusible and filtrable aı:ıd relatively heat-stable. it lost its activity when
neutra-iized with Na OH.
KARASOY (10) fçmnd salmonella cannot survive more than 44 ho-urs in yogurt, but E. eoli can survive 60 hoho-urs.
According to GÜRSEL and FİşEK (7) yogurt has a bactericidal
acÜ~n against E. eoli, S. typhi, Shig. paradysenteriae (Flexner), Br. me. litensis, C. diphtheriae, K. pneumoniae (Friedlander), and Pr.
ı
9, x but not for St. hemolytie\ls, Type A.GÜRSEL and FİşEK ('7) found, in 1953. that the bactericidal
aeti-on of the micro-organisms of yoğurt depends on the amount of lactic
acid produced by Laet. Bulgarieus.
POLYMENAKOS (9) states that patients who are treated wi.th
auromycin or teramycin wiIl not develop gastro-intestinal
disturban-ces if theyare given yogurt.
According to GÜRSEL (6) yogurt has a bactericidal action aga
inst Myeobaeterium tubereulosis typus humanus and bovinus but not
against the gallinaeeous type.
METCNİKOFF mentioned the bactericidal properties of yogurt.
. For centuries yoğurt has been used in Turkev as 2. treatment
[or-distÜ~bances of the digestive tract. . .
The albumin and casein are in part transformed into digestible
peptones and albuminoses in yogurt by bactenal action (22).
The Micro-organisms of Yoğurt
REFİK and ŞADİ (19) mention three kin ds of micro-organisms
in yogurt as follows : i. BaciIli :
2 - Homogen bacillus 3 - Delicate bacillus II. Diplococci : III. Yeasts : 1 - Oval yeasts 2 - Oblong yeasts
According to IZMEN (9) the best yoğurt culture will have two
kinds of organisms :
«1 - Thermobacterium (yoğurt, bulgarieum) .
2 - Streptococcus thermophilus»
and will not contain other hacteria, yeasts, or molds.
GÜRSEL and FİşEK (7) state yoğurt has three kinds of micro
-organisms :
1 - Streptococcus thermophilus
2 -. Lactobacillus bulgaricus
3 - Saccaromyces
According to AYOÜN (1) the microflora of yoğurt incIude seven
different organisms.
ROSSEL (22) and BROCHU (2) say S. theımophilus, L.
bulgari-cus, and Plocamobacterium yoghourtü are the essential of yoğurt.
PENKO (14) isolated S.thermophilus and L. bulgaricus from
yo-ğurt. He described their cultural and physiological charaeteristics. PETTE and LOLKEMA (16), (17) stated the correct balance
bet-ween Lactobacillus sp. S. thermophilus should be 1/1 in the test
cul-tures. They regarded these organisms as t~e essential ones.
According to VLEESCHAUWER, OKERMAN, and NAUDTS (27)
the yoğurt microrIora are a mixture of L. bulgaricus and S. thermophi. lus. In some instances they found ro ds which cIosely resembled L. casei
or cocci which differed from S. thermophilus by fai1ing to ferment
glucose, galactose, and saccharose.
OMURTAG, OMURTAG, and ORDAL (12) isolated S. thermophi-lus, 'a lactobacilthermophi-lus, and two kinds of yeast from Turkish Yoğurt.
Presumably KERN's Dispora caucasicum, BEYERİNCK's Bact.
ca-ucasicum, PREUDENREICH's Bact. caucasicum (21), İZMEN's
Ther-mobacterium yoğurt (9), and ROSELIı's (22) and BROCHU's (2)
plo-camobacterium yoghurtii are idenUcal with REFİK and şADİ's BaciL.
of Turk.
it is suggested to consider the taxonomy of Lact. bulgaricus as
Turkish Regulations Concering Yoğurt
Turkish regulations conceming yoğurt are as follows (26)
CHAPTER.2.
Section V
Yoğurt
Paragraph 50 : Yoğurt is a lactic fermentation product availabI
for human eonsumption which is produced by adding yoğurt cultur
to boiled milk. .
Yoğurt can be made from either whole milk or 50 % whole an
50 % skim milk of cows, sheep, water buffalo, or goats. According to
Paragraph 23: Torba yoğurt made from skim milk may be sold. But it
is unlawful to seıı any other type of yoğurt made from skim milk.
Paragraph 51 : Constituents of Yoğurt
% Fat' % Non-fat dry solids
Whole milk of cows 3 8
Whole milk of sheep 6 10
Whole milk of water buffalo 7 ~. 9
Whole milk of goats 4 .. .... ... . 8.5
50 % skim milk of cows 2 8
50 % skim milk of sheep 4 10
50 % skim milk' of water buffalo 4.6... 8
50 % skim milk of goats 3 8.5
The consistency, appearance, odor; and tests must be natural.
Yog1ırt may be made by mixing not more than two kinds of mik
in equal parts. The fat content of such yoğurt must at least egual half the sum of the fa;t content of each of the two milks used in the mixtu-I
re. The required non-fat dry solids content is at least half the sum of the non-fat dry solids of each of the two types of milk combined to
pro-du ce the mixture. .
Paragraph 52 : The cont2jner must be covered with a waterproof
paper. The container must carry alabel whieh identifies the type of
yoğurt (made from whole milk, made from 50 % whole and 50 % skim milk, or torba yoğurt). gives the type of milk use d (cows', sheep, 2tc,),
lists the net weight, gives the date of produetion, and names the firm
Paragraph 53: The addition of stareh, any kind of animal fat; ete.
is prohibited. Yo~rt eontaining dirt or any foreign material must not
be sold. Torba yoğurt may contain 2 %' of salt.
Paragraph 54 : Dirty, spoiled, rancid, moldy or imprcperly fermen- •
ed yo~rt or yo~rt made from unhealthy milk can not be sold.
Paragraph 55 : Containers which affect the yo~rt or permit its
contamination by unsanitary material must not be used.
EXPERIMENT S
MATERİAL: Twenty samples of yo~rt made from 50% whole and
5U % skim milk of cows were bought in Ankara in July
1958.-METHOD : The method which v.rasuse d in this study was the
mo-dification of BABCOCK method for the detetmination of fat content
of yo~rt by OMURTAG and TUCKEY (3).
RES1JLTS
Number ol samples % "of Icd c:oııtent Number ol scunples" % ol Icd coııtent
1 ... 2.8 11
...
2.2 2...
2.8 12...
2.0 3 ... 2.8 13...
2.4 4...
2.6 14...
2.2 5...
1.9 15...
2.4 6...
2.2 16 ... 2.2 7...
2.5 17...
2.2 8 ... 2.5 18...
2.4 2.2 19.
9 ......
2.5 10...
2.2 20...
2.2Table (1): % of fat eontent of the samples.
DISCUSSION
According to the Turkish Regulations, Paragraph 51, the fat
con-tent of 50 % whole and 50 % skim milk of- cows yo~rt should be 2
%. In this study the fat content of the only 5 % of the samples were
below the legal limit.
'SUMMARY.
In this study the fat content of 20 samples of 50 % whole and
!LO % skim milk of cows yo~rt were determined by the modification of
Accortong to this study thecontent of 5 % of the samples were la wer than the legal limit, 5 % were at the legal level and 90 % were hig
her than the minimum legal limit.
ÖZET
Denemeye alınan 20 adet yarım yağlı ine k yoğurdunun yağ muht
vısı OMURTAG ve TUCKEY tarafından modifiye edilmiş olan
BAB-COCK metodu ile tayin edilmiştir.
Bu çalışmaya göre, numunelerden 1/20 sinin yağ muhtevisi, yanın
yağlı ine k yoğurduna ait kanuni hadden aşa~, 1/20 si tam kanuni limit
üzerinde ve 18/20 sinin de kanl\Ili hadden yüksek olduğu bulunmuştur.
LiTERATÜR
] - AYGÜN, S.T. 119401 : Hayvanlardan elde edilen gıdalar. gıda hıfzıssıhlıası ve gıda tahlili : T.C. Ziraat Vekaleli. Talepe Derskılavuzu. Sayı 16. Sahife. 48,' _
489.
2 - EROeBU. S. 119351 : The eommereial manulacture ol yoghurt mUk,. milk Plant Monthly 24. 5. 37 .. Bak: BURK:EY. L. A. (1947) : How to ma!:e yogJı.url.
BDiM-Inf-2. ,
3 - DAMKAa, F (1954): Therapeutie uses of yoğurl. New York., Bak: YÖNEY. Z. (1957) : İnsan sağlığında yoğurl.. A. Ü.. Ziraat Fakültesi 1957 yıllığı lasıkül 2
Sahife 190 - 20ı. i
.ı -
GOLEM, S. B. (1944) : Eberthe]Ja typhosa'nın Ankara ayranlarında yaşa:ııa müddeti. Hıfzıı;ıhha ve Teerü"~i Biyoloji Dergisi 45 - GÜ:'MEZOGLU, E., v•• FİŞEK, N. H. (1956) : i. Yoğulta riboflavin. Biolin vp Nikotinik asit .mildarı. Türk İjyün ve Teerübi Biyoloji Dergisi. Cilt xvı, sayı 3. sahife 222-227
ii - GÜRSEL, A. (1957) : Le F~uvoir Bacterieide du Yoğhurt Sur le Myeobaeteriunı Tubereulosis. Türk İjyen ve Teerübi Biyoloji Dergisi, Cilt XVıı. sayı. I.II sabire 40 - S8,
7 - GÜRSEL, A, ve FİşEK, N. B. (1953) : Yoğurt Plorası ve Yoğurdun Bakterisil tesiri. Türk İjyen ve Teerübı Biyoloji Dergisi Cilt xııı . Sayı: i. Sahife: 79.87 B - HONDA, Y. (938) : Bacjeriologieal observations on sour milk in Inner M.:>r..
golia" Dairy Scienee Abstr, 1939.40 Vol. ı. P. 69.
9 -
İZMEN, E. R. (1955) :Süt ve maınülleri bilgisi ders ki!'ıbı. Ankara Ün .. Zire:a! Fakültesi Yayınları: 63, Cers K:tabı 28.(O - KABASOY, M. (1952) : Men~eı hayvoni gıda konservelerin':!eı. bazıları üze .. rinde tetkikat ve hayvanlardan gıda vasıtası ile insanlara bulaşan mikroplonr. gıda konservelerinde yaşama müddeli. Ankara Üniversitesi Veteriner Fakültesi yayınları 31. 77-81.
i i - Mahmiidüı - Kaşqari (J 066) : Divan. al - lügat . at . Türk. (See. ÜRESİN. E. R., (935) : Silivri yoğurfunun yapılışı ve terhbi hakkında araştırmalar T. C. Yüksek Ziraat Enstitüsü çalışmalarından. sayı LI. sahife. i I.
2 OMUR'lAG. A. C •. OMURTAG. E. H .. and OBDAL, Z. J. (1957) : The Mierob:oi. ogy of Turkish yoğurl. Universily of III., U. S. A., Unpublished dala.
'1 OMURTAG. A. C .• and TUCKEY. S. L. (ı957) The study on fal conlenıaf Tur-kish yoğurl. Universily of III .• U. S. A. Unpublishe-d dala.
4 PENKO. P. (1955) : The micraflora of yoğun .. Dairy Science Absır, 1955, Vci. 17, No. h. P. 503.'
S PETTE. J. W .. and LOLKEMA. H. (1950) : Yağlıurt. III. Acid produelion and are ma rormalion in yoğhurl.. Dairy Science Absır .. 1952. Vol-14. No.~ 5. P. :;50 6 _ PETTE. J. W. anda LOLK'EMA. R. (1951) : Yoğhurl. IV Foelors irrfluencing lhe
proporlion ai streptocoeci and iaclobaciili ın a yoğhurl eullure. Dairy Seienee Absır., 1952, VoL. 14 No. 5. P. 35ı.
7 PETTE. J, W. and LOLKEMA. R. (1950) : Yoğhı:rl ı. Symbiosis and antibiosıs in mixed eullers of Laclobacillus bulgarieus and S.lreplocoeeus lhermophilus. Dairy Science, Absır. Vol. 14. No. 5. P. 350.
18 POLYMENAKOS. L. G. (954) : Anlibiolic enterocnlilis .. Dairy Scienee Abstr, 1954. vol. 16. No. 6. P. 478
19 -._ REFİK ve ŞADİ (1924>' Yoğurt hakkında baklerilojik lelkikalı ve TürkbasH; İslanbul Hıfsıhha Müessesesi Neşriyalından. 1-16.
20 _ llEICREL. M. (955) : Yoğhurl produclion with P. H. canlrol.. Dairy Scienct! Absır., 1955 VoL. 17. No 6 P. 472.
21 _ ROGERS. L. A. (1916) : Revised by ALBUS W. R. (1928): Fermenlei Milkı; United S. Deparı. of .Agr. Deparment Bullelin No. 319. 20-23.
22 _ R05ELL. J. M. (1935) : The manufacture of popular European special milkB. milk Dealer. 24-7,41 .. Bak: BURKEY. A. (1947): Hcw lo make yoğhurl. BDIM-Inf - 2., U. S., Depl. Agr. Agrieulcural Ressarch Adminislration, Bureau of Dairy Induslry.
23 _ RUDANOVSKAYA, A. (1955) : Tablels for lhe preparalion of SOUr mUk pro-duels: Dairy Science Absır. 1955. Vol. 17. No. ı. P. 473.
24 _ SENECA. H .. HENDEJlSON. E.. and COLLINS, A. (1950) : Baelerial properlies of yoğhurl.', Dairy Science Absır, 1951. Vol. 13. No. 4. P. 492.
25 _ SOULIDES. D. A. (1955) : A. synerqism between yoğhurl baeleria and yeasls and lhe elfeel of their associalion upon the viability of the baeleTia. Appl
Mierobiology. Voı 3. No. 3. P. 129-131.
26 _ T. C. Sağlık Sosyal yardım Bakanlığı. (1952) Gıda maddelerınin ve UmumI Sağlığı ilgilendiren Eşya ve Levazırnın Husus; vasıflarını gösteren lüzük. p..r..
kara Başbakanlık Devlet Maıbaası. Yayın No. 16ı. Sahife: 13-15.
27 _ VLEESCHAUWEB, lL DE .. OKERMJ1N. F. and NAYDTS. M. 119541: Th-e Prop-erlies of lhe yoğhurt baderia, Dc1iry Scieınce Absır, 1955. Vol. 17, No. 6 P. ~.'i, 28 _ YÖNEY. Z. 119571 : İnsan sağlığında yoğurl.. A. Ü. Ziraal Faküllesi 1957 yıllığı.
Fasiklil 2, Sahile 190 - 20 i
29 ~ YUSUF HASRACİB (1064) : Kuladgu - Bilig (see ÜRESİN, E. A. (19351 SiliYri yoğurlunun yapılu; ve lerkibi hakkında araştırmalar - C. Yüksek Zircıal E~~. litüsü çalışmalarından. sayı II. Sahife: i O
