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Journal ArticleDOI

Fatty acid profile and cholesterol content of Ghezel sheep milk during lactation period

27 Oct 2017-Acta Alimentaria (Akadémiai Kiadó)-Vol. 46, Iss: 4, pp 457-463

TL;DR: The chemical composition, fatty acid profile, and cholesterol content of milk fat were analysed during the lactation period of thirty Iranian Ghezel sheep when they were fed dry hay for the first three months and grazed on fresh grass to the end of lactation.
Abstract: The chemical composition, fatty acid profile, and cholesterol content of milk fat were analysed during the lactation period of thirty Iranian Ghezel sheep. They were fed dry hay for the first three months and then grazed on fresh grass to the end of lactation, along with barley and wheat middling during the whole period. Fatty acid profile analysis showed palmitic acid to be the dominant fatty acid (45.24±1.88%). During lactation C6:0, C8:0, C10:0, C12:0, and C14:0 contents decreased, while C18:0, C18:1, C18:2, and CLA increased significantly, which can be associated with the change of nutrition from hay to fresh grazing. The cholesterol content of the sheep milk reached 14.88 mg/100 ml milk or 283.43 mg/100 g fat as an average for the whole period of milking. Regression analysis showed a significant increase in cholesterol from 5.42 to 32.87 mg/100 g milk during the lactation period.
Topics: Sheep milk (59%), Lactation (57%), Fatty acid (54%), Hay (53%), Palmitic acid (52%)

Summary (2 min read)

Introduction

  • Iran (received: 3 December 2016; accepted: 23 January 2017).
  • The effect of lactation period on milk composition in different sheep breeds have been studied by several authors (KUCHTIK et al., 2008), but the results do not support each other probably because of different factors that may change sheep milk composition (NUDDA et al., 2002) According to the FAO (2014) reports, Iran ranks eighth in the world for sheep milk production, which is about 5% of the total milk production by country.
  • The sheep in the region are mostly, more than 95%, of the Ghezel breed, which has been noted as one of the two distinctive milk type breeds in Iran (VALIZADEH, 2010).
  • Therefore, the aim of the present study is to evaluate the major chemical components, fatty acid profi le, and cholesterol content of sheep milk throughout the lactation period in order to report an average for the content and needed changes in the procedure during the lactation period to help dairy technologists, cheese producers, nutritionists, and physicians.

1.1. Animals feeding and sampling

  • The study was carried out on thirty Iranian Ghezel sheep, maintained in the most experienced and biggest traditional farm of the region, Eidi.
  • The manuscript contains experimental animals, the study was conducted in accordance with the internationally accepted principles for laboratory animal use and care, and their ethical committee on animal care approved the protocol.
  • All of the selected animals were in good condition and clinically healthy.
  • They were numbered and fed the same diet as all cattle, a prevalent way of feeding in the region.
  • Milk samples were gathered from each encoded sheep every month from two weeks of parturition after the colostrum stage to the end of lactation lasting about six months.

1.2. Chemical composition analysis

  • Milk samples were analysed for fat, protein, lactose, and total solids (TS) contents using MilkoScan (Minor 78100, FOSS, Denmark), which was calibrated each month before the tests.
  • Soluble nitrogen content was detected by the standard Kjeldahl method according to the AOAC 16.041 (1990).
  • 1.3. Fatty acid profi le Fatty acid composition of the frozen milk samples was determined with the direct transesterifi cation method as proposed by LEPAGE and ROY (1986).
  • The injection volume was 1 μl and the split ratio was set at 1:100.
  • Injection and detection temperatures were 240 °C and 260 °C, respectively.

1.4. Cholesterol analysis

  • After centrifugation at 2000 g, the upper phase was separated for injection to GC (FLETOURIS et al., 1998).
  • The column was capillary TRB sterol (30 m × 0.22 mm × 0.22 μm) (Teknokroma, Italy).
  • Oven temperature was set at 285 °C, while injection temperature was 300 °C.
  • Equal concentrations of standard cholesterol and alphacholestane (as internal standard) were prepared and injected to GC.
  • The resulted peak areas were divided to reach a factor (F).

1.5. Statistical analysis

  • One-way analysis of variance and subsequent comparison of means by the least signifi cant difference (LSD) method at 5% probability level was carried out.
  • Chemical composition was assessed by regression model.
  • Software including SAS and SPSS were used for statistical calculations.

2.1. Milk composition

  • Chemical composition of milk samples from thirty sheep (Ghezel breed) gathered during the six months of the lactation period is shown in Table 1.
  • Breed could also be an important factor that identifi es sheep milk composition (BOCQUIER & CAJA, 1999).
  • It can be concluded that fat, protein, and TS contents increased, while lactose content decreased during the lactation period.
  • Medium-chain fatty acids of C10:0, C12:0, C14:0, and C16:0 contributed to 62% of the total in this study, while the short-chain fatty acid (SCFA) content of C4:0, C6:0, and C8:0 was 4.05%.
  • Milk is an important source of CLA that could respond to more than 75% of human Acta Alimentaria 46, 2017 nutritional demands.

2.3. Cholesterol content

  • The cholesterol content of the sheep milk was obtained as 14.88 mg/100 ml milk as an average for the whole period.
  • Considering the average fat content of the milk (5.25 g/100 g milk), the cholesterol content could be reported as 283.43 mg/100 g fat.
  • GOUDJIL and co-workers (2003) have reported a range between 15–30 mg/100 ml milk and 288 mg/100 g fat.
  • WOJTOWSKI and co-workers (2001) reported 26.11 mg/100 ml milk for sheep milk, as well.
  • Regression analysis of cholesterol content during the lactation period showed a signifi cant increase (P<0.05).

3. Conclusions

  • It can be concluded that with the progress of lactation, the fat, protein, and total solids content of sheep milk increased, while lactose content decreased signifi cantly.
  • Furthermore, the sheep milk of the region had a high protein and low fat content compared to other reports.
  • Fatty acid profi le analysis showed palmitic acid to be dominant, with permanent content during lactation period.
  • The cholesterol content of the sheep milk increased towards the end of lactation independent of fat content.
  • The authors kindly acknowledge supports from the Tabriz Branch, Islamic Azad University, Tabriz, Iran.

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0139–3006 © 2017 Akadémiai Kiadó, Budapest
Acta Alimentaria, Vol. 46 (4), pp. 457–463 (2017)
DOI: 10.1556/066.2017.46.4.8
FATTY ACID PROFILE AND CHOLESTEROL CONTENT OF GHEZEL
SHEEP MILK DURING LACTATION PERIOD
A. ALIZADEH
a
*, M.R. EHSANI
b
and L. ROFEHGARINEJAD
a
a
Department of Food Science and Technology, Tabriz branch, Islamic Azad University, Tehran Rd., 5157944533,
Tabriz. Iran
b
Department of Food Science and Technology, Science and Research Branch, Islamic Azad University,
Daneshgah Blvd, Simon Bulivar Blvd, 1477893855, Tehran. Iran
(received: 3 December 2016; accepted: 23 January 2017)
The chemical composition, fatty acid pro le, and cholesterol content of milk fat were analysed during the lactation
period of thirty Iranian Ghezel sheep. They were fed dry hay for the rst three months and then grazed on fresh grass
to the end of lactation, along with barley and wheat middling during the whole period. Fatty acid pro le analysis
showed palmitic acid to be the dominant fatty acid (45.24±1.88%). During lactation C6:0, C8:0, C10:0, C12:0, and
C14:0 contents decreased, while C18:0, C18:1, C18:2, and CLA increased signi cantly, which can be associated
with the change of nutrition from hay to fresh grazing. The cholesterol content of the sheep milk reached 14.88
mg/100 ml
milk or 283.43 mg/100 g fat as an average for the whole period of milking. Regression analysis showed
a signi cant increase in cholesterol from 5.42 to 32.87 mg/100 g milk during the lactation period.
Keywords: chemical composition, cholesterol, fatty acid, milk, sheep
Milk has an important role in human nutrition due to its complex nutrients that meet the
metabolic and growth needs. Although milking cows produce a signi cant proportion of
worldwide milk production, small ruminants, such as goats and sheep, have a special place
regarding the speci c composition of their milk and its impact on health (STRZALKOWSKA et
al., 2009). Considering that dairy goat and sheep farming are a vital sector in some
Mediterranean and Middle Eastern economies, they require development towards becoming
more industrial. Information on the composition of sheep milk and related products would be
essential for this to occur (PARK & HAENLEIN, 2006). Milk composition is affected by several
factors such as breed, stage of lactation, milking system, health, environment, and feeding
(BOCQUIER & CAJA, 1999; KUCHTIK et al., 2008). The effect of lactation period on milk
composition in different sheep breeds have been studied by several authors (KUCHTIK et al.,
2008), but the results do not support each other probably because of different factors that may
change sheep milk composition (NUDDA et al., 2002)
According to the FAO (2014) reports, Iran ranks eighth in the world for sheep milk
production, which is about 5% of the total milk production by country. The sheep in the
region are mostly, more than 95%, of the Ghezel breed, which has been noted as one of the
two distinctive milk type breeds in Iran (VALIZADEH, 2010). The population of this breed is
about 1.8 million in Iran, and classi ed as fat-tail, heavy weight ones with mean lactation
yield of 100–220 kg (IZADIFARD & ZAMIRI, 1997; BANEH et al., 2013). Sheep milk in the region
is mostly processed as cheese. Lighvan is a village in a mountainous area in the province of
* To whom correspondence should be addressed.
Phone: +98 912 3309182; e-mails: a.alizadeh@iaut.ac.ir, ainaz_alizadeh@hotmail.com

458
ALIZADEH et al.: FATTY ACID AND CHOLESTEROL CONTENT OF SHEEP MILK
Acta Alimentaria 46, 2017
Azerbaijan in Iran, and is famous for its speci c semi-hard sheep-milk cheese. Although
Lighvan cheese's composition has been analysed in several papers, there is no study that
investigates this breed's milk composition. Meanwhile, studies on the cholesterol content of
sheep’s milk is limited to just a few studies and needs to be distinguished more with details
of different breeds.
Therefore, the aim of the present study is to evaluate the major chemical components,
fatty acid pro le, and cholesterol content of sheep milk throughout the lactation period in
order to report an average for the content and needed changes in the procedure during the
lactation period to help dairy technologists, cheese producers, nutritionists, and physicians.
1. Materials and methods
1.1. Animals feeding and sampling
The study was carried out on thirty Iranian Ghezel sheep, maintained in the most experienced
and biggest traditional farm of the region, Eidi. The manuscript contains experimental
animals, the study was conducted in accordance with the internationally accepted principles
for laboratory animal use and care, and our ethical committee on animal care approved the
protocol. Research has been done in the veterinary Faculty, Tabriz branch, Islamic Azad
University that is under supervision of the Science minister of Iran. The sheep were selected
with the help of a veterinarian in charge of milking the region’s animals. All of the selected
animals were in good condition and clinically healthy. They were numbered and fed the same
diet as all cattle, a prevalent way of feeding in the region. For the rst three months of
lactation (February–April), feeding was with dry hay in caves, but throughout the second
three months (May–July), hay was substituted with free fresh grazing. Barley and wheat
middling were also added to their diet during the period of lactation. This method of feeding
was similar to that of the other sheep keepers in the region, without any changes made in
order to attain the actual milk composition in the area. Milking was carried out by a combined
lamb-suckling and hand-milking procedure during the suckling period and by twice daily
hand-milking from weaning to the end of lactation. Lambs were weaned about 100 days after
lambing. Milk samples were gathered from each encoded sheep every month from two weeks
of parturition after the colostrum stage to the end of lactation lasting about six months. Milk
samples were kept in a freezer at –45 °C for analysis.
1.2. Chemical composition analysis
Milk samples were analysed for fat, protein, lactose, and total solids (TS) contents using
MilkoScan (Minor 78100, FOSS, Denmark), which was calibrated each month before the
tests. Soluble nitrogen content was detected by the standard Kjeldahl method according to the
AOAC 16.041 (1990).
1.3. Fatty acid pro le
Fatty acid composition of the frozen milk samples was determined with the direct
transesteri cation method as proposed by LEPAGE and ROY (1986). A 100 ml milk sample was
mixed with 2 ml methanol:benzene (4:1) and then 200 ml acetyl chloride was added. The
methanolised sample was kept at 45 °C
for 1 h, 5 ml K
2
CO
3
was added to cooled vials, and
nally it was centrifuged at 2000 g. The upper phase was injected to GC.

459ALIZADEH et al.: FATTY ACID AND CHOLESTEROL CONTENT OF SHEEP MILK
Acta Alimentaria 46, 2017
1.3.1. Gas chromatography (GC). GC (Model 610, Buck Scienti c, USA) was equipped
with a ame ionization detector and capillary column (TR-CN100, fused silica, 60 m ×
0.25 mm × 0.2 μm lm thickness, Teknokroma, Italy). The injection volume was 1 μl and the
split ratio was set at 1:100. Injection and detection temperatures were 240 °C and 260 °C,
respectively. The initial temperature of the oven was set at 190 °C for eight min, and then
increased with a rate of 1 °C min
–1
to reach 260 °C. Helium was used as the carrier gas with
a ow rate of 2 ml min
–1
. Fatty acid methyl esters were identi ed by comparison of their
retention times with authentic standards analysed under the same conditions. Results were
expressed as % w/w of total fatty acid.
1.4. Cholesterol analysis
1.4.1. Sample preparation. Five ml KOH was added to 0.5 g milk and mixed for 15 s. The
lower phase was heated at 80
°C
for 15 min and vortexed every ve minutes for 10 s. Then, 1
ml of water and 5 ml hexane were added to the sample and shaken vigorously for 1 min. After
centrifugation at 2000 g, the upper phase was separated for injection to GC (F
LETOURIS et al.,
1998).
1.4.2. GC condition for cholesterol analysis. The column was capillary TRB sterol (30
m × 0.22 mm × 0.22 μm) (Teknokroma, Italy). The detector was FID adjusted at 300 °C.
Oven temperature was set at 285
°C,
while injection temperature was 300 °C. Carrier gas was
helium with a ow rate of 3 ml min
–1
. Injection volume was 1 μl.
1.4.3. Quantitative analysis. Equal concentrations of standard cholesterol and alpha-
cholestane (as internal standard) were prepared and injected to GC. The resulted peak areas
were divided to reach a factor (F).
An identi ed quantity of internal standard (50 μg) was added to the sample and injected
to GC. The nal concentration of cholesterol was quanti ed by multiplying 50 F and
cholesterol peak area, which accordingly divided by internal standard peak area.
1.5. Statistical analysis
One-way analysis of variance and subsequent comparison of means by the least signi cant
difference (LSD) method at 5% probability level was carried out. Chemical composition was
assessed by regression model. Software including SAS and SPSS were used for statistical
calculations.
2. Results and discussion
2.1. Milk composition
Chemical composition of milk samples from thirty sheep (Ghezel breed) gathered during the
six months of the lactation period is shown in Table 1. Total average chemical composition
was obtained as: fat=5.41±1.48, protein=6.58±0.78, lactose=4.79±0.80, and total solids
17.52±2.03 (% w/w) (mean ± SD). Comparing these data with literature revealed an
unexpected result related to protein content, which was more than fat content, while most
studies have reported the opposite (PARK et al., 2007). In order to analyse this result, soluble
nitrogen and, accordingly, the casein content of the samples were detected. Casein content

460
ALIZADEH et al.: FATTY ACID AND CHOLESTEROL CONTENT OF SHEEP MILK
Acta Alimentaria 46, 2017
was 79±3% (mean ±SD) of the total protein, which was quite normal. This means that the
higher proportion of protein content in the sheep milk did not correlate with whey proteins
that might originate from diseases or other factors. Higher protein content could be related to
nutrition, in that a high level of nutrition and energy balance will decrease fat content and
increase protein content in sheep milk (BOCQUIER & CAJA, 1999). Furthermore, cereals in the
diet reduce acetate synthesis in the rumen, which is a precursor of fat (PULINA et al., 2006).
Breed could also be an important factor that identi es sheep milk composition (BOCQUIER &
CAJA, 1999). In the rst month, the average fat content of the samples in this study was very
low. Samples were aimed to be gathered after second weeks of parturition, where there was
a sharp increase in milk yield as reported by IZADIFARD and ZAMIRI (1997) in the second week
from lambing for Ghezel sheep.
Table 1. Sheep milk chemical composition across the 6 months of lactation
Lactation
months
Fat (%) Protein (%) Lactose (%) TS (%)
Mean SD Mean SD Mean SD Mean SD
1
st
2.61 0.83 5.46 0.65 5.57 0.15 14.42 0.83
2
nd
4.91 1.43 5.78 0.54 5.31 0.24 16.64 1.23
3
rd
5.16 1.15 6.65 0.66 5.07 0.22 17.46 1.06
4
th
5.60 1.08 7.09 0.70 4.65 0.29 18.04 1.40
5
th
5.27 1.01 7.25 0.56 4.82 0.15 17.89 1.06
6
th
7.93 1.24 9.03 2.46 3.29 1.44 20.67 2.21
LSD (5%) 1.02 1.03 0.55 1.23
Data are mean±SD (n=30). LSD (5%): Least Signi cant Difference at P<0.05
Milk composition changes during lactation were signi cant (P<0.05), the results of
which are shown in Table 1. It can be concluded that fat, protein, and TS contents increased,
while lactose content decreased during the lactation period. In milk of sheep and other cattle,
at the peak of lactation with maximum lactose synthesis, protein and fat synthesis cannot
keep up with the lactose increase (NUDDA et al., 2002). It was obvious in our study that at the
rst half of lactation lactose synthesis was high, but it decreased towards the end, because of
the lower milk yield. Sharp changes in sheep milk composition at the sixth month were
related to the very low daily milk yield that decreased from 1600 g at rst month to about 200
g at sixth month. It would therefore be advisable to study a ve-month period of lactation in
future studies. Fat content did not change signi cantly between the second and fth month,
while the maximum protein content was reported for the fourth and fth months (P<0.05)
excluding the sixth month. The lowest and highest lactose contents occurred at the fourth and
rst months, respectively, and nally, the lowest total solids content was recorded for the rst
month (P<0.05).
2.2. Fatty acid pro le
Fatty acid pro les of the sixty milk samples gathered during the six months of lactation are
shown in Table 2. Palmitic acid was the dominant fatty acid. Although, high palmitic acid is

461ALIZADEH et al.: FATTY ACID AND CHOLESTEROL CONTENT OF SHEEP MILK
Acta Alimentaria 46, 2017
a feature of the majority of mammals, in this study the content was more than twice the oleic
acid content (45.24 vs. 21.08%), while most studies have reported approximately equal
percentages of the two fatty acids (JANDAL, 1996; PARK et al., 2007; CARLONI et al., 2009).
Medium-chain fatty acids (MCFAs) of C10:0, C12:0, C14:0, and C16:0 contributed to 62%
of the total in this study, while the short-chain fatty acid (SCFA) content of C4:0, C6:0, and
C8:0 was 4.05%. Obviously, C4:0 and C10:0 percentages were less and palmitic acid contents
were higher than previously reported by PARK and co-workers (2007). Such results could
relate to nutrition and the cereals rich in palmitic acid that were added to the sheep’s diet.
Other signi cant factors such as race, climate, and some other minor elements could also be
important.
Table 2. Sheep milk fatty acids pro le during six months of lactation period
Fatty
acid
(%)
Months of lactation
1st
Mean ±SD
2nd
Mean ± SD
3rd
Mean ±SD
4th
Mean ±SD
5th
Mean ± SD
6th
Mean ± SD
LSD
5%
C4:0 0.97 0.14 0.86 0.28 0.68 0.21 0.83 0.22 0.81 0.29 0.81 0.36 0.13
C6:0 2.73 0.66 2.37 1.00 1.89 0.56 1.12 0.36 1.24 0.24 0.95 0.46 0.18
C8:0 2.59 0.48 2.13 0.87 1.75 0.37 0.97 0.26 1.12 0.24 0.60 0.32 0.16
C10:0 4.85 1.17 4.17 1.46 3.78 1.12 1.69 0.52 2.02 0.47 0.99 0.55 0.23
C12:0 3.58 0.96 3.11 0.84 3.24 1.04 1.52 0.40 1.81 0.30 1.08 0.39 0.19
C14:0 13.30 1.19 14.42 1.26 14.87 2.13 8.83 1.84 11.42 0.72 9.14 3.08 0.25
C15:0 0.85 0.38 0.90 0.35 0.79 0.13 0.84 0.17 1.10 0.17 0.84 0.20 0.11
C16:0 45.64 2.99 46.36 4.14 45.74 2.50 41.85 3.67 47.26 1.56 44.60 2.98 0.21
C16:1 1.34 0.24 1.24 0.23 1.45 0.29 2.23 0.68 1.45 0.46 1.82 0.31 0.14
C18:0 6.90 1.14 7.29 1.05 7.19 1.11 9.24 2.32 9.10 0.77 9.06 2.51 0.24
C18:1 15.85 2.39 15.76 1.97 17.17 2.60 28.84 3.78 20.64 1.85 28.26 5.09 0.30
C18:2 1.33 0.33 1.20 0.21 1.27 0.23 1.75 0.29 1.62 0.32 1.60 0.30 0.11
CLA 0.09 0.05 0.20 0.12 0.18 0.08 0.29 0.17 0.42 0.15 0.28 0.10 0.10
Data are mean±SD (n=30). LSD (5%): Least Signi cant Difference at P<0.05
Changes in fatty acid pro le during the lactation period were signi cant except for C4:0,
C15:0, C16:0, and C16:1 (P<0.05). Regression analysis for the fatty acids indicated that
during lactation, C6:0, C8:0, C10:0, C12:0, and C14:0 contents decreased, while C18:0,
C18:1, C18:2, and CLA contents increased signi cantly (P<0.05). This should be in
accordance with the change of nutrition from hay to fresh grazing.
Fatty acids of 4–14 carbon atoms are synthesized de novo in the mammary gland, while
C18 acids are take in from the circulating blood. C16:0 originates from both, and is less
altered (HUPPERTZ et al., 2009).
Polyunsaturated fatty acid (PUFA) content is very important, as these fatty acids have
an impact on health. In particular, CLA has such biological activity (STRZALKOWSKA et al.,
2009). Milk is an important source of CLA that could respond to more than 75% of human

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TL;DR: This one-step direct transesterification procedure carried out in methanol-benzene 4:1 with acetyl chloride is superior to currently used methods not onlyBecause of its simplicity and speed, but also because of its added precision.
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Abstract: Physico-chemical characteristics of milk are related to its composition for a particular animal species. Sheep milk contains higher levels of total solids and major nutrient than goat and cow milk. Lipids in sheep and goat milk have higher physical characteristics than in cow milk, but physico-chemical indices (i.e., saponification, Reichert Meissl and Polenske values) vary between different reports. Micelle structures in goat and sheep milk differ in average diameter, hydration, and mineralization from those of cow milk. Caprine casein micelles contain more calcium and inorganic phosphorus, are less solvated, less heat stable, and lose β-casein more readily than bovine casein micelles. Renneting parameters in cheese making of sheep milk are affected by physico-chemical properties, including pH, larger casein micelle, more calcium per casein weight, and other mineral contents in milk, which cause differences in coagulation time, coagulation rate, curd firmness, and amount of rennet needed. Renneting time for goat milk is shorter than for cow milk, and the weak consistency of the gel is beneficial for human digestion but decreases its cheese yield. Triacylglycerols (TAG) constitute the biggest part of milk lipids (nearly 98%), including a large number of esterified fatty acids. Sheep and goat milk also have simple lipids (diacylglycerols, monoacylglycerols, cholesterol esters), complex lipids (phospholipids), and liposoluble compounds (sterols, cholesterol esters, hydrocarbons). The average fat globule size is smallest ( 75% of total fatty acids in goat and sheep milk. Levels of the metabolically valuable short and medium chain fatty acids, caproic (C6:0) (2.9%, 2.4%, 1.6%), caprylic (C8:0) (2.6%, 2.7%, 1.3%), capric (C10:0) (7.8%, 10.0%, 3.0%), and lauric (C12:0) (4.4%, 5.0%, 3.1%) are significantly higher in sheep and goat than in cow milk, respectively. Principal caseins (CN) in goat, sheep and cow milk are αs1-CN, αs2-CN, β-CN and κ-CN. The main forms of caprine and ovine caseino-macropeptides (CMP), which are the soluble C-terminal derivatives from the action of chymosin on κ-casein during the milk clotting process of cheesemaking, have been identified and are a good source of antithrombotic peptides. Sheep and goat milk proteins are also important sources of bioactive angiotensin converting enzyme (ACE) inhibitory peptides and antihypertensive peptides. They can provide a non-immune disease defence and control of microbial infections. Important minor milk proteins include immunoglobulins, lactoferrin, transferrin, ferritin, proteose peptone, calmodulin (calcium binding protein), prolactin, and folate-binding protein. Non-protein nitrogen (NPN) contents of goat and human milks are higher than in cow milk. Taurine in goat and sheep milk derived from sulphur-containing amino acids has important metabolic functions as does carnitine, which is a valuable nutrient for the human neonate. Mineral and vitamin contents of goat and sheep milk are mostly higher than in cow milk.

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J. M. Jandal1Institutions (1)
TL;DR: This paper deals with changes in milk constituents due to heat treatments as well as dairy products produced from these species to focus international attention on the dairy products which can be produced a large scale in many countries.
Abstract: The purpose of this paper is to review the several differences in physico-chemical, medical, nutritional, biological, radioactivity and immunological aspects of goat and sheep milk. It also deals with changes in milk constituents due to heat treatments as well as dairy products produced from these species to focus international attention on the dairy products which can be produced a large scale in many countries.

218 citations


Journal ArticleDOI
Abstract: This review discusses current knowledge of the main nutritional factors that influence composition of sheep milk and, consequently, its processing into cheese, with special focus on milk fat and protein concentration and characteristics, content of bioactive compounds, somatic cell content, content of aromatic compounds able to improve its organoleptic characteristics and content of toxic substances. Sheep milk composition is strongly influenced by ewe nutrition, especially in highly productive animals. Milk fat concentration is markedly affected by the ewe's net energy (NE) balance, dietary NDF content and dietary supplementation with ruminally protected/inert or unprotected marine and vegetable oils. Milk fat composition can be modified to contain higher levels of human healthy fatty acids (FA), such as conjugated linoleic acid and omega-3 FA. Milk protein content, and its characteristics, are more difficult to change than milk fat, although dietary energy seems to have a major role, while diet protein and amino acid supplementation only marginally affect milk protein level and its characteristics. Nutritional stress, and some vitamins, affect the somatic cell content of milk and this impacts cheese yield and quality. Feeds in the diet can markedly influence milk aroma and, consequently, play a role in determining cheese flavor, especially when ewes are pastured. Possible sources and causes of contamination of sheep milk by heavy metals or dioxins, and mycotoxins, through the diet are also addressed. Overall, quality and safety of sheep milk can be modified and improved by the nutrition characteristics of the diet.

158 citations


Journal ArticleDOI
TL;DR: Overall recovery was 98.6%, and the linearity was excellent for the fortification range examined, which suggested an overall relative standard deviation value of 1.4%.
Abstract: A simple method is described for the determination of cholesterol in milk and milk products. Samples (0.2 g) are saponified in capped tubes with 0.5 M methanolic KOH solution by heating for 15 min at 80 degrees C. Water is added to the mixtures, and the unsaponifiable fractions are extracted with hexane to be further analyzed by capillary gas chromatography. Because of the rapid sample preparation and gas chromatographic procedures, a single sample can be analyzed in 30 min. Overall recovery was 98.6%, and the linearity was excellent for the fortification range examined. Precision data that were based on the variation within and between days suggested an overall relative standard deviation value of 1.4%. The method has been successfully applied to quantitate cholesterol in a variety of milk products.

121 citations