alexa Variation of Fatty Acid Content in Zamorano-Type Ovine Cheese According to the Milk Conjugated Linoleic Acid Content | Open Access Journals
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Variation of Fatty Acid Content in Zamorano-Type Ovine Cheese According to the Milk Conjugated Linoleic Acid Content

Domingo Fernández1, Ricardo Arenas1, Carlos Gonzalo2*, Eliana Barbosa2, Bernardo Prieto1, Carlos Palacios3, L. Fernando De La Fuente2 and José María Fresno1

1Departamento de Higiene y Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de León,24071-León, Spain

2Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, 24071-León, Spain

3Departamento de Construcción y Agronomía, Facultad de Ciencias Agrarias y Ambientales, Universidad de Salamanca, 37007 Salamanca, Spain

*Corresponding Author:
Gonzalo C
Departamento de Producción Animal
Facultad de Veterinaria, Universidad de León, Spain
Tel: +34987291115
E-mail: [email protected]

Received date: September 03, 2015 Accepted date: September 30, 2015 Published date: Octomber 02, 2015

Citation: Fernández D, Arenas R, Gonzalo C, Barbosa E, Prieto B, et al. (2015) Variation of Fatty Acid Content in Zamorano-Type Ovine Cheese According to the Milk Conjugated Linoleic Acid Content. J Adv Dairy Res. 3:147. doi:10.4172/2329-888X.1000147

Copyright: © 2015 Gonzalo C, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract

A total of 30 Zamorano-type cheeses were manufactured in order to study the effects of milk conjugated linoleic acid (CLA) content, ripening time, and interactions between both effects on fatty acid (FA) profile. Cheeses elaborated from milk with a high CLA content showed higher contents of vaccenic, oleic, alpha-linolenic (ALA), CLA, monounsaturated (MUFA) and polyunsaturated (PUFA) FA, and lower contents of capric, lauric, myristic, palmitic, estearic, linoleic, and saturated (SFA) FA than cheese from milk with a low CLA content. Content of unsaturated C18 FA along with MUFA and PUFA groups increased throughout the ripening, while SFA content decreased. The interactions between milk CLA content and ripening time were significant for palmitic, linoleic, CLA, SFA, and omega-6/omega-3 ratio in Zamorano-type cheese. Decreases in cheese omega-6/omega-3 ratio were obtained from milk with a high CLA content; this ratio worsened over ripening in cheeses from low-CLA milk. In conclusion, these results emphasize the importance of the initial CLA content in milk with regard to improve the lipid profile in cheese for consumption.

Keywords

Sheep; Cheese; Fatty acids; Conjugated linoleic acid

Introduction

The world cheese production in 2010 was 20.698 thousand tonnes, 50% of which were produced in European countries [1], the mean consumption of cheese in several Mediterranean countries being greater than 20 kg per person and year. Ewe milk is a product that is high in fat and protein and is mainly used for commercial or artisanal cheeses. Fatty acids (FA) in cheese are becoming more and more important because of the link between the FA content in the diet and certain illnesses. Nevertheless, fat in dairy foods also contain compounds which can improve health like butyrate, sphingolipids, conjugated linoleic acid (CLA) and omega-3 [2,3]. The CLA is a mixture of positional and geometric isomers of octadecadienoic acid with conjugated double bond system. Omega-3 FA are a form of essential polyunsaturated fat, the most nutritionally notable being alpha-linolenic acid (C18:3 cis-9, cis-12, cis-15; ALA) in milk and cheese products. Biomedical studies with animal models have evidenced several profitable properties (anticarcinogenic, antiatherogenic, antioxidant, antiobesity, antidiabetic, etc) attributed to CLA [4,5], omega-3 [6,7], and other FA, which have been related to human health because of their unsaturated nature [8,9]. In addition, the relationship among FA in the final product is also important. Western diets are deficient in omega-3 FA, and have excessive amounts of omega-6 FA compared with the diet on which human beings evolved and their genetic patterns were established [10]. In addition, excessive amounts of omega-6 polyunsaturated FA and a very high omega-6/omega-3 ratio, as is found in today's Western diets, promote the pathogenesis of many diseases, including cardiovascular disease, cancer, and inflammatory and autoimmune diseases, whereas increased levels of omega-3 (a lower omega-6/omega-3 ratio), exert suppressive effects [11]. These aspects are of great interest in the cheese, which is a fat-product highly consumed in industrialized countries. In this context, the cheeses made from ewe's milk are characterized by a greater CLA content than those from other species [12] and there is evidence that the consumption of naturally enriched cheese in ALA, CLA and vaccenic FA possesses beneficial properties, since it ameliorates the plasma lipid profile and reduces endocannabinoid biosynthesis in hypercholesterolaemic subjects [13].

Factors influencing variation of FA content in ovine milk, such as flock, lactation stage, parity number, season or day of testing, have been studied in a previous paper [14], but very little information is disposable on the transference of these FA from milk to cheese and on the evolution of lipid profile during ripening [15]. In this sense, the variation of cheese lipid profile in function of milk CLA content could be of interest with view to final FA content because the cheese represents the main source of CLA for human consumption and an attempt should be made to know the relationship between the lipid profiles of milk and cheese and monitor their stability during cheese elaboration and ripening. Thus, we hypothesized that CLA level of milk is a main factor improving the final lipid profile of cheese for consumption.

Zamorano cheese is one of the best known among the ripened Spanish cheeses protected with designation of origin; it is a semi-hard non-cooked cheese, salted in brine, and produced in the Castilla and León region (Spain) from ewe´s milk. The shape is cylindrical (height and diameter less than 14 and 24 cm, respectively) and the weight range from 2.8 to 3.0 kg.

The objectives of this study were: first, to determine the transfer of main FA and FA groups from ewe’s milk to Zamorano-type cheese in function of milk CLA level, second, to evaluate the importance of ripening time on cheese FA content, and third, to study the interactions between both effects. The results of the study will provide valuable information for future efforts to maximize the content of CLA and other beneficial FA in cheese products.

Materials and Methods

Sampling and cheese making

From the recording system of bulk tank milk lipid profile implemented in the flocks of the Association National of Churra sheep (ANCHE) in Castilla and León region (Spain), 3 dairy sheep flocks with high, medium and low CLA content were selected for this experiment. From bulk tank milk of these 3 flocks, 3 batches (150 L of milk each) of 5 Zamorano-type cheeses per batch were manufactured in duplicate (75 L of milk per manufacture) in order to study the effect of several factors influencing the FA content in the cheese. The effects tested were the FA content provided by the milk of high, medium, and low CLA content, and the ripening time. The 3 batches corresponded with the design shown in Table 1. All cheeses were made according to the next cheese making procedure. Pasteurized ewe´s milk with calcium chloride (0.2 g/L) is warmed to 30-32ºC and a commercial lyophilized starter culture (MA11, 0.8%; Table 1) was added after milk pasteurization. After 30 min of milk acidification, 25 mL of commercial lamb rennet (80% chymosin; 75 Rennet Units) were added per 100 L of milk. Coagulation took place over 35–40 min and the curd was cut until a size of a grain of rice. The curd was then heated to 37–38ºC, being continuously stirred until it reached the desired consistency.

Batch no. CLA content
(g/100 g of total fatty acids)
Heat treatment Coagulation type Starter culture (0.8%) Ripening time (days)
1 High
C18:2 cis-9, trans-11 (CLA): 1.83
C18:2 trans-10, cis-12 (CLA): 0.04
Pasteurized milk Enzymatic MA111 1, 60, 120, 180, 240
2 Low
C18:2 cis-9, trans-11 (CLA): 0.48
C18:2 trans-10, cis-12 (CLA): 0.01
Pasteurized milk Enzymatic MA111 1, 60, 120, 180, 240
3 Medium
C18:2 cis-9, trans-11 (CLA): 0.82
C18:2 trans-10, cis-12 (CLA): 0.02
Pasteurized milk Enzymatic MA111 1, 60, 120, 180, 240

Table 1: Design of three batches of Zamorano cheese manufactured from ovine milk with high, low and medium CLA content.

1CHOOZITTMMA11LYO25DCU (Danisco, Sassenage, France): Lactococcus lactis subsp. lactis + Lc. lactis subsp. cremoris.

The whey was drained off and the curd was transferred to cylindrical moulds 14 cm deep by 24 cm diameter, and pressed over 4–5 hr until they reach a pH of 5.4–5.5. The curds with their characteristic cylindrical shape were salted in brine (17–18 ºBaumé; pH 5.4 and temperature 8-10 ºC) for between 16 and 18 hr. Finally, the cheeses were stored in ripening rooms at a temperature of approximately 10–12 ºC and a relative humidity of 85% for 240 days.

For each batch, duplicate one whole cheese of 3 kg was sampled at the ripening days indicated in Table 1. The cheese rind was discarded and the cheeses were minced and stored in hermetic containers at -30ºC until they were analyzed. The total number of cheeses analyzed was 30.

Milk samples were transported to the laboratory under refrigeration, were taken from each batch prior to addition of rennet and analyzed within 24 hr of sampling.

Analytical methods

The methods used in the analysis of basic chemical composition of milk were total solids by IDF Standard 021 [16]; protein by IDF Standard 020-5 [17]; fat by IDF Standard 105 [18]; lactose by IDF Standard 214 [19]. The pH was directly measured with a pHmeter GLP 22 (Crison, Barcelona, Spain). Titratable acidity was measured according to AOAC Standard 947.05 [20].

Dry matter, fat and salt in cheese were determined according to IDF Standards 004 [21] and 222 [22], and AOAC Standard 935.43 [23], respectively. The pH and titrable acidity of cheeses were measured using AOAC Standards 14022 [24] and 920.124 [25], respectively. Cheese water activity was determined by Aqualab Dew Point Analyzer (Decagon Devices Inc., Pullman, WA, USA).

Milk fat extraction was carried out by the method of Bligh and Dyer [26] using chloroform and methanol. Fat of cheese samples were extracted by the method of De Jong and Badings [27]. Lipid extracts were stored at −30°C until further analysis. Fatty acid analysis and identification was carried out according to methodology previously describes [14]. Briefly, fatty acid methyl esters (FAME) were prepared by base-catalyzed methanolysis of glycerides (NaOCH3) according to Aldai et al. [28]. FAME were separated by gas chromatography using a Tekno TR-CN 100 capillary column (60 m × 0.25 mm i.d. × 0.2-µm film thickness; Teknokroma, Barcelona, Spain) on a Hewlett-Packard chromatograph (model 6890, Wilmington, DE) equipped with an automatic injector (model 7683, Hewlett-Packard) and a mass selective detector (model 5973, Hewlett-Packard). The injection and detector temperatures were 230ºC. Helium was used as a carrier gas at a flow rate of 1 mL/min. Samples (1 µL) were injected into a split injector (split ratio 10:1).

Reference standards were used to determine recoveries and correction factors for individual FA (Supelco 37 Component FAME MIX and linoleic conjugated acid methyl ester, Sigma-Aldrich, Bellafonte, PA, USA).Identification of fatty acids and trans isomers was carried out by retention time and quantified by comparing the retention times and areas of their peaks to those observed for their respective standards, using nonanoic acid (C9) as an internal standard. The individual FA contents were expressed as weight percentages (g/100 g of total FA). All analyses were made in duplicate.

Dependent variables for the study of variation factors

Although 36 FA were initially determined analytically (Table 2), the statistical study of the variation factors was restricted to the most important 13 FA, 6 groups of FA, and 1 FA index, all of which were treated as dependent variables. The groups, which were based on the saturation level and chain length, were as follows: sum of saturated FA (SFA), sum of short-chain saturated FA (C4 to C10, SCFA), sum of medium-chain saturated FA (C12 to C15, MCFA), and sum of long-chain saturated FA (C16 to C24, LCFA). The 2 remaining groups were the sum of monounsaturated FA (MUFA), and the sum of polyunsaturated FA (PUFA). The index considered was the omega-6/omega-3 ratio, being omega-6 the sum of linoleic (C18:2 cis-9, cis-12) + gamma linolenic (C18:3 cis-6, cis-9, cis-12) + araquidonic (C20:4 cis-5, cis-8, cis-11, cis-14) FA, and omega-3 the ALA (C18:3 cis-9, cis-12, cis-15). The criteria for selecting the 13 FA as dependent variables were as follows: 1) considering the 11 quantitative most important FA, with percentages above 2.0% [14], and 2) including 2 additional FA of biological interest, which are CLA and ALA.

  Milk Cheese
Trait1,2 Median SD Minimum Maximum CV(%) Median SD Minimum Maximum CV(%)
C4:0 2.30 0.21 2.13 2.54 9.38 2.30 0.25 2.05 3.51 11.09
C6:0 2.20 0.10 2.09 2.29 4.61 2.29 0.17 2.03 2.78 7.51
C8:0 3.19 0.20 2.97 3.36 6.26 3.29 0.25 2.40 3.52 7.60
C10:0 8.53 0.13 8.39 8.63 1.51 8.26 0.57 7.33 9.34 6.95
C12:0 4.64 0.04 4.59 4.67 0.94 4.87 0.33 4.38 5.66 6.84
C13:0 0.16 0.01 0.15 0.18 9.35 0.16 0.03 0.10 0.22 21.95
C14:0iso 0.13 0.02 0.11 0.15 16.43 0.15 0.01 0.11 0.17 9.91
C14:0 9.70 0.34 9.31 9.92 3.52 9.68 0.42 9.05 10.51 4.38
C15:0iso 0.40 0.01 0.39 0.41 2.50 0.38 0.03 0.32 0.45 9.10
C14:1 cis-9 0.59 0.03 0.56 0.62 5.21 0.65 0.07 0.49 0.77 11.79
C15:0 1.13 0.01 1.12 1.14 0.88 1.24 0.08 1.09 1.38 6.81
C16:0iso 0.43 0.06 0.36 0.47 14.14 0.43 0.06 0.16 0.52 15.20
C16:0 22.21 2.21 19.68 23.73 9.94 21.63 1.98 19.62 25.02 9.17
C17:0 1.12 0.23 0.86 1.32 21.05 0.88 0.20 0.59 1.22 22.59
C16:1 cis-9 1.63 0.10 1.52 1.70 6.04 1.49 0.13 1.22 1.77 8.43
C17:0antiso 1.11 0.12 1.00 1.24 11.04 0.98 0.10 0.76 1.21 10.58
C18:0iso 0.14 0.02 0.13 0.16 12.37 0.15 0.03 0.08 0.20 20.88
C17:1 cis-10 0.42 0.09 0.32 0.48 21.17 0.36 0.09 0.14 0.47 23.88
C18:0 10.05 0.60 9.46 10.66 5.97 10.28 0.55 9.37 11.29 5.37
C18:1 trans-11 2.76 0.24 2.60 3.05 8.91 2.82 0.27 2.39 3.21 9.54
C18:1 cis-9 17.11 1.55 16.07 18.90 9.08 17.54 1.45 14.78 19.89 8.28
C18:1 cis-11 0.79 0.07 0.74 0.87 9.19 0.80 0.08 0.67 0.92 9.77
C18:1 cis-12 0.69 0.07 0.65 0.77 9.60 0.70 0.07 0.59 0.81 9.61
C18:2 trans-9, trans-12 0.51 0.03 0.47 0.53 6.79 0.70 0.29 0.38 1.18 41.72
C18:2 cis-9, cis-12 4.14 0.14 3.99 4.26 3.32 3.82 0.51 3.13 4.85 13.49
C20:0 0.37 0.03 0.33 0.39 9.36 0.36 0.04 0.29 0.47 11.10
C18:3 cis-6, cis-9,cis-12 0.04 0.01 0.03 0.06 35.25 0.06 0.01 0.03 0.10 26.68
C20:1 cis-9 0.02 0.01 0.01 0.03 50.00 0.03 0.01 0.01 0.05 30.98
C18:3 cis-9, cis-12, cis-15(ALA) 1.28 0.20 1.05 1.41 15.76 1.50 0.36 0.95 2.04 24.38
C18:2 cis-9, trans-11 (CLA) 1.04 0.70 0.48 1.83 67.30 1.11 0.48 0.67 1.81 43.00
C18:2 trans-10, cis-12 (CLA) 0.02 0.01 0.01 0.04 65.46 0.03 0.01 0.01 0.04 38.41
C21:0 0.18 0.06 0.14 0.25 33.79 0.18 0.07 0.11 0.30 40.47
C22:0 0.24 0.05 0.20 0.30 23.27 0.20 0.03 0.13 0.25 16.06
C20:4 cis-5, cis-8,cis-11,cis-14 0.41 0.05 0.35 0.44 12.13 0.43 0.11 0.22 0.68 24.57
C23:0 0.16 0.01 0.15 0.16 3.68 0.13 0.02 0.10 0.18 19.66
C24:0 0.13 0.01 0.11 0.14 12.06 0.10 0.02 0.07 0.13 14.57
SFA 68.52 2.94 65.12 70.26 4.30 67.95 2.79 64.00 72.79 4.11
SCFA 16.22 0.21 15.99 16.38 1.27 16.13 0.72 14.82 17.84 4.49
MCFA 16.16 0.36 15.75 16.38 2.21 16.49 0.59 15.56 17.44 3.57
LCFA 36.13 2.65 33.07 37.81 7.35 35.32 1.92 32.79 38.49 5.44
MUFA 24.02 2.05 22.48 26.35 8.53 24.40 2.04 20.54 27.54 8.37
PUFA 7.45 0.99 6.57 8.53 13.35 7.65 0.84 6.28 8.96 10.96
Ratio omega-6/omega-3 3.64 0.61 3.23 4.34 16.79 3.10 1.05 1.75 4.96 33.88

Table 2: Basic statistics of milk (n=3) and Zamorano-type cheese (n=30) fatty acid content.

Statistical analysis

The statistical analysis was carried out by the GLM procedure of SAS [29]. The model used was:

Yijk=μ+Ci+Rj+CRij+eijk

where Yijk refers to the 20 dependent variables of cheeses; that is, 13 FA, 6 groups of FA, and 1 FA index previously described. The factor Ci was the CLA level of milk (3 levels: high, low, and medium; Table 1). The factor Rj was the ripening time of cheese (5 levels: 1, 60, 120, 180, 240 days; Table 1). The factor CRij was the interaction between CLA level of milk and cheese ripening time. The factor eijk was the residual effect. Water activity, pH, titratable acidity, total solids, fat and salt content of cheeses were non-significant co-variables for the most of the dependent variables, and were excluded from the statistical models.

This research was carried out in accordance with EU Directive 2010/63/EU for animal experiments.

Results and Discussion

The statistics of the FA studied in milk and cheese are shown in Table 2. Similarly to other studies in ovine milk [14,30], some of the SFA, such as palmitic (C16:0, 22.2% and 21.6%), stearic (C18:0, 10.1% and 10.3%), capric (C10:0, 8.5% and 8.3%), myristic (C14:0, 9.7% and 9.7%), and lauric (C12:0, 4.6% and 4.9%) acids had relatively high contents in milk and cheese, respectively (Table 2). Similarly the contents of oleic acid (C18:1 cis-9, 17.1% and 17.5%) and linoleic acid (C18:2 cis-9 cis-12, 4.1% and 3.8%) were also high in milk and cheese, respectively. The C18:2 cis-9 trans-11 CLA isomer had a similar content in milk (1.04%) and cheese (1.11%), lower than the content of vaccenic (C18:1 trans-11, 2.8% and 2.8%) and ALA (C18:3 cis-9, cis-12, cis-15, 1.3% and 1.5%) acids. High SFA (68.5% and 68.0%), LCFA (36.1% and 35.3%) and MUFA (24.0% and 24.4%) contents, and low PUFA (7.5% and 7.7%) content and omega-6/omega-3 ratio (3.6 and 3.1) were also observed in ovine milk and cheese, respectively. Quantitative contents in FA, FA groups and FA index were very similar in both products; thus, a close relationship could be predicted between the milk and cheese lipid profiles.

Table 3 showed the test of significance for all studied effects on cheese FA profile. The CLA content and ripening time significantly contributed to variation of final FA profile. The importance of CLA content x ripening time interaction was lesser.

The CLA content of milk significantly contributed (p<0.001) to variation of the CLA and other FA related (ALA, linoleic, oleic, and vaccenic) in the cheese because the relationship among the unsaturated C18 FA family [14]. Also, CLA content of milk significantly influenced (p<0.001) the variation of MCFA and LCFA (C12:0 to C18:0), such as lauric, myristic, palmitic, and stearic FA (Tables 3 and 4).

Variable1 CLA content (df=2) Ripening time (df=8) Interaction (df=8) R2
C4:0 0.47NS 0.78NS 0.69NS 0.39
C6:0 5.36* 1.23NS 3.93* 0.76
C8:0 1.64NS 2.09NS 2.10NS 0.65
C10:0 4.65* 12.52*** 1.71NS 0.83
C12:0 32.17*** 5.57** 2.65* 0.88
C14:0 22.93*** 14.16*** 0.99NS 0.88
C16:0 89.36*** 24.39*** 7.28*** 0.96
C18:0 37.77*** 2.42NS 1.15NS 0.86
C18:1 trans-11 259.53*** 61.70*** 8.08NS 0.98
C18:1 cis-9 107.35*** 27.76*** 2.30NS 0.96
C18:2 cis-9, cis-12 127.84*** 11.71*** 9.29*** 0.96
C18:3 c-9, c-12, c-15(ALA) 225.40*** 7.79** 3.48* 0.97
C18:2 cis-9, trans-11 (CLA) 2838.84*** 13.21*** 4.84** 0.99
SFA 156.98*** 38.46*** 5.18** 0.97
SCFA 4.25* 5.06** 0.43NS 0.93
MCFA 45.00*** 24.25*** 3.93* 0.94
LCFA 75.20*** 12.67*** 3.89* 0.94
MUFA 143.35*** 34.61*** 3.70* 0.97
PUFA 45.28*** 10.98*** 3.56* 0.92
Ratio omega-6/omega-3 480.84*** 0.87NS 4.94** 0.98

Table 3: Analysis of variance (F values, significance and R2 of the model) for fatty acid content in Zamorano-type cheese

Variable1,2 Low Medium High p-value
C4:0 2.30a 2.36a 2.24a NS
C6:0 2.38a 2.21b 2.28ab *
C8:0 3.31a 3.35a 3.19a NS
C10:0 8.47a 8.29ab 8.02b *
C12:0 4.98a 5.10a 4.55b ***
C14:0 9.95a 9.76a 9.34b ***
C16:0 22.75a 22.47a 19.66b ***
C18:0 10.49a 10.69a 9.65b ***
C18:1 trans-11 2.68b 2.67b 3.12a ***
C18:1 cis-9 16.71b 16.81b 19.10a ***
C18:2 cis-9, cis-12 4.16a 4.05a 3.25b ***
C18:3 cis-9, cis-12, cis-15(ALA) 1.07c 1.55b 1.88a ***
C18:2 cis-9, trans-11 (CLA) 0.73c 0.83b 1.77a ***
SFA 69.66a 69.24a 64.96b ***
SCFA 16.46a 16.21ab 15.73b *
MCFA 16.79a 16.71a 15.99b ***
LCFA 36.41a 36.32a 33.24b ***
MUFA 23.32b 23.25b 26.62a ***
PUFA 7.01c 7.51b 8.43a ***
Ratio omega-6/omega-3 4.40a 2.94b 1.96c ***

Table 4: Least squares means for fatty acid content in Zamorano-type cheese by CLA content level of milk (low, medium and high).

With the only exception of linoleic acid, Table 4 showed increased values (p<0.001) of unsaturated C18 FA family in cheeses manufactured from milk with high CLA content in comparison with those values found in cheeses obtained from milk with low CLA content. In addition, milk CLA content affected the cheese content of stearic, palmitic, myristic and lauric FA (p<0.01 to p<0.001), but in a negative sense (Table 4), probably due to the negative correlations among CLA content and C12, C14, C16 and C18 saturated FA contents.

As a whole, cheeses elaborated from milk with a high CLA content showed increased (p<0.001) vaccenic, oleic, ALA, CLA, MUFA and PUFA contents and decreased lauric, myristic, palmitic, estearic, linoleic, SFA, MCFA, LCFA contents and omega-6/omega-3 ratio (Table 4).Indeed, according results evidenced in Table 4, omega-6/omega3 ratio was much improved in the cheeses with a high CLA content (1.96) in comparison with cheeses with a low CLA content (4.40).

These results evidenced that cheeses elaborated from milk with a high CLA content improved their lipid profile from the point of view of human health, by increasing the content of CLA, ALA and unsaturated FA and decreasing omega-6/omega-3 ratio.

The effect of ripening time is showed in Table 5. The content of all unsaturated C18 FA along with MUFA and PUFA groups increased (p<0.01 to p<0.001) throughout the ripening, while SFA content decreased (p<0.01 to p<0.001).Therefore, cheese with long ripening periods showed a healthier lipid profile than those with short ripening ones due to beneficial FA enrichment over ripening. These results were also in agreement with those obtained by [31] for the transfer of C18:1 and C18:2 FA isomers from ewe’s milk to Peccorino Toscano cheese.

Variable1,2 Ripening time (days) p-value
1 60 120 180 240  
C4:0 2.47a 2.25a 2.24a 2.28a 2.24a NS
C6:0 2.31a 2.28a 2.22a 2.36a 2.26a NS
C8:0 3.23a 3.20a 3.46a 3.36a 3.18a NS
C10:0 8.38b 8.49ab 8.87a 7.78c 7.79c ***
C12:0 4.84bc 5.03ab 5.05a 4.70c 4.76c **
C14:0 9.75b 9.83b 10.09a 9.34c 9.40c ***
C16:0 22.91a 22.50ab 21.86b 20.52c 20.35c ***
C18:0 10.24a 10.16a 10.08a 10.41a 10.52a NS
C18:1 trans-11 2.66c 2.72b 2.74b 2.99a 3.00a ***
C18:1 cis-9 16.69b 17.09b 16.93b 18.51a 18.49a ***
C18:2 cis-9, cis-12 3.67b 3.66b 3.71b 4.05a 4.02a ***
C18:3 cis-9, cis-12, cis-15(ALA) 1.47b 1.41b 1.42b 1.61a 1.60a **
C18:2 cis-9, trans-11 (CLA) 1.07b 1.08b 1.09b 1.16a 1.18a ***
SFA 69.44a 68.96a 69.07a 66.17b 66.12b ***
SCFA 16.40a 16.21a 16.80a 15.78b 15.47b **
MCFA 16.49b 16.72b 17.05a 16.00c 16.20c ***
LCFA 36.55a 36.03a 35.22b 34.39c 34.44c ***
MUFA 23.17b 23.73b 23.67b 25.70a 25.73a ***
PUFA 7.39b 7.31b 7.26b 8.14a 8.16a ***
Ratio omega-6/omega-3 3.08a 3.03a 3.04a 3.16a 3.18a NS

Table 5: Least of squares means for cheese fatty acid content by ripening time (days) in Zamorano-type cheese.

In addition, several authors [12,31,32] found that C18:2 cis-9, trans-11 isomer increased between 10% and 26% on total content of CLA during ripening of different cheeses, which is also compatible with our results.

This CLA increase has been associated to hydrogen donors in processed cheese [33]. Nevertheless, in other studies [34] the cis-9, trans-11 CLA decreased as consequence of biohydrogenation or of double bonds isomerisation, while the concentration of trans-10, cis-12 CLA increased.

The interactions between milk CLA content and ripening time were important effects (p<0.01) for palmitic, linoleic, CLA, SFA, and omega-6/omega-3 ratio in Zamorano-type cheese (Table 6).Thus, linoleic and CLA FA increased over ripening for cheeses manufactured from milk with low and medium CLA levels, whereas linoleic decreased and CLA showed a small variation over ripening from milk with a high CLA level. An opposite trend was found for SFA. The ratio omega-6/omega-3 increased (p<0.05) throughout the ripening in cheeses manufactured from milk with a low CLA content, and remained unchanged for medium CLA contents. These interactions have not been studied up to now and would explain some discrepancies about the CLA evolution over ripening found by several authors [12,31,32,34].

Variable1,2 Ripening time (days) p-value
1 60 120 180 240  
C16:0           7.28***
High CLA 19.67a 19.74a 19.62a 19.64a 19.63a  
Low CLA 24.74a 24.36a 22.60b 21.67b 20.36c  
Medium CLA 24.32a 23.39a 23.36a 20.23b 21.06b  
C18:2 cis-9, cis-12           9.29***
High CLA 3.46a 3.33a 3.17b 3.13b 3.14b  
Low CLA 3.94b 3.88b 4.00b 4.37a 4.62a  
Medium CLA 3.61d 3.76dc 3.95c 4.64b 4.30a  
C18:2 cis-9, trans-11 (CLA)           4.84**
High CLA 1.81a 1.72b 1.73bc 1.79ac 1.80a  
Low CLA 0.67c 0.74ab 0.71bc 0.75ab 0.80a  
Medium CLA 0.72c 0.77bc 0.81b 0.93a 0.93a  
SFa           5.18**
High CLA 65.25ab 65.03ab 66.26a 64.04b 64.20b  
Low CLA 71.13a 71.43a 70.39a 68.26b 67.08b  
Medium CLA 71.93a 70.41b 70.57b 66.19c 67.07c  
Ratio omega-6/omega-3           4.94**
High CLA 1.99ab 2.11ab 2.14a 1.79ab 1.76b  
Low CLA 4.30b 4.03b 4.09b 4.72a 4.85a  
Medium CLA 2.95a 2.94a 2.91a 2.96a 2.94a  

Table 6: Least of squares means for cheese fatty acid content by ripening time (days) in Zamorano-type cheese.

Conclusions

The lipid profile of ovine cheese was significantly influenced by CLA content of milk and ripening time. The highest vaccenic, oleic, ALA, CLA, MUFA and PUFA contents were for cheeses elaborated from milk with a high CLA content, and at the end of ripening time. On the contrary, SFA were highest in cheeses from a low-CLA milk and at beginning of ripening. Omega-6/omega-3 ratio was more beneficial in cheeses originated from milk with a high CLA content; this ratio worsened over ripening in cheeses from a low-CLA milk. As a whole, these results emphasize the importance of the initial CLA content in milk with regard to improve the lipid profile in cheese for consumption.

Acknowledgments

This work was supported by the Spanish Ministry of Science (Madrid, Spain; project AGL2005-04321) and the Castilla and León regional government (Junta de Castilla y Leon, Valladolid, Spain) by a grant for research groups of excellence (UIC number 056). The authors are grateful to ANCHE farmers for their participation in this study.

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