1. Introduction

In the past, food quality was more related to sensory, shelf-life and safety aspects of food products, but more recently it is associated with nutrition and health ^[1]. Meat and meat products are generally recognized as highly nutritious foods that provide valuable amounts of vitamins, minerals, fatty acids (FA) and other bioactive compounds ^[2], and consumers consider meat to be a healthy and important component of the diet ^[3].

Moreover, beef consumption become more important in China due to the improving economy and dietary habits change ^[4]. Beef consumption is promoted for the health benefits because of its nutritional value including vitamin and mineral content, but criticized for the high proportion of saturated fatty acid (SFA) in fat fraction especially in subcutaneous and intermuscular fat ^[5]. SFA increases plasma cholesterol and low density lipoprotein (LDL) levels ^{[6, 7, 8]}, promotes development of atherosclerosis leading to coronary heart disease (CHD) or cardiovascular disease (CVD) ^{[8, 9, 10]}, whereas polyunsaturated fatty acids (PUFA), especially n-3 serial PUFA, reduces the risk of CHD ^{[11, 12]}. Monounsaturated fatty acids (MUFA) as well as n-3 PUFA are recognized as benefit for health ^{[13, 14, 15]}. Previous studies confirm that FA profiles can be influenced by numerous factors such as breed ^{[16, 17, 18]}, diet ^{[19, 20]} and different regions ^[21]. Duckeet also reported that cooking can increase stearic acid and total SFA contents of intramuscular lipid and reduce total PUFA content ^[22].

On the other hand, the use of the microwave oven for cooking has increased considerably during the past few decades^[23]. There are numerous reports on the cooking of meat using microwaves. During microwave cooking, the air surrounding the meat is cold and water evaporating from meat which makes the meat condensed ^[24]. Microwave cooking also changes flavor qualities of food in a lesser extent as opposed to conventional heating ^[25]. Microwave cooking is caused by the ability of the food materials (mainly the moisture or water in food) to absorb microwave energy and convert it into heat. However, microwave can generate high temperature may affect the oxidation of the lipids and quantitatively change the FA composition ^{[26, 27]}. Garcı́a-Arias, Álvarez Pontes ^[28] found SFA increased, but n-3 PUFA reduced in sardine with microwave processing. Maranesi, Bochicchio ^[29] reported FA composition changed in lamb due to microwave treated, however limited research is available to document changes in FAs composition of beef with microwave cooking.

Previous studies have focused on nutritional value related to changes in FA composition during cooking ^{[29, 30, 31]}. However, few studies have examined the effects of different thermal treatment on FA of different lipid fractions ^{[22, 32]}. The objective of this study was to assess changes in FAs composition of the neutral lipid (NL), polar lipid (PL), and total lipid (TL) with boiling and microwave cooking, and evaluate the implications to human health.

2. Materials and Methods

Ten bulls of Chinese Yellow Cattle (live weight, 463 ± 35kg) ranging from 18 to 24 months of age were used in current experiment. Animals were pen-housed, fed with the common diet pattern including alfalfa, maize silage, and long-stem hay, followed by a diet consisting of maize for three months. The animals were slaughtered in a commercial meat processing abattoir (Changchun Haoyue Islam Meat Co. Ltd.) in northeastern China. After 2 days of chilling (0-2°C), carcasses were segmented, then semitendinosus muscles were obtained from left side. All samples were prepared 25mm thickness each, vacuum packed, and stored at -20°C until use.

Beef samples were thawed in room temperature (about 10°C) for 24 h and one steak sampled was used directly as the control (uncooked raw beef steak with room temperature about 10°C). Samples were individually placed inside polyethylene bags and cooked in a boiled water bath for approximate 60s, 130s, and 250s to get the final internal temperatures of 60°C, 70°C and 80°C respectively. Internal temperature was determined using thermocouples piercing probes attached to a thermometer. In microwave cooking treatment, preliminary testing was conducted first to attain the final internal temperature needed. Beef samples were placed in separate glass dishes in a pan placed in the centre of the carousel of a 2450 MHz, 700W variable power oven (G70F20N2L-DG(SO), Galanz, China). The power control was set at 350W for 30s, then shut down the microwave oven for 10s to permit the internal heat equilibration, and measured the internal temperature of beef samples with digital thermocouples piercing probes outside the microwave oven, and then went on with the repeated procedure of microwave cooking (30s) - shutting down (10s) - measuring internal temperature until the internal temperature reaching 60°C, 70°C or 80°C. Each treatment was conducted with three replications.

Beef samples were dissected free of intermuscular fat and the epimysium. The content of NL, PL and TL were extracted by Dry Column method ^[33], as described briefly below. Beef samples (2g) were ground in a 750ml porcelain mortar with granular anhydrous sodium sulfate (8g) and then with diatomaceous earth (6 g), and the resulting mixture was packed above an 1:9 CaHPO₄/diatomaceous earth trap (4g) in a glass chromatography column (16mm id×25cm with 8mm id×5cm drip tip) and charged first with 80ml of dichloromethane, when the last of the dichloromethane reached the top of the column packing, the volumetric flask (100ml) containing the collected eluate (NL) was replaced by a second 100ml flask, and the column was charged with 80ml of the 9:1 (v/v) CH₂Cl₂/MeOH solvent mixture. The first (NL) and second flasks (PL) were vacuum distilled in relatively low temperature (25°C). Another 2g of the sample was processed in the same manner, instead of charging with 80ml of the 9:1 solvent mixture directly, the third flask (TL) was collected and vacuum distilled.

The saponification, methylation, and FAs analyses of NL, PL and TL were based on the methods of ^{[34, 35]}, and the AOCS ^[36]. Lipids were saponified using methanolic NaOH and methylated using a freshly prepared methanolic BF₃ solution. The dry methanol solution of FA methyl esters was stored at 0°C in a refrigerator until analysis. To determine the FA composition, 100 mg of the extracted lipid was dissolved in 2ml of hexane and added with 50μg of heneicosanoic acid methyl ester (21:0, Augsburg, Germany) as an internal standard. For all steps in the procedure the extract was blanketed with nitrogen. Methylated lipid samples were analyzed using a flame ionization detector (FID) on a gas chromatograph (Shimadzu GC14A, Kyoto, Japan) equipped with a 50m × 0.32mm capillary column (CP-Sil 88, Varian Inc., CA, USA). Both injector and detector temperatures were set at 280°C. The initial oven temperature was 160°C, held for 2min, raised by a gradient of 5°C/min to 220°C, and held for 30min, for a total run time of 44 min. The pressures of the gases were 0.8kg/cm² for the carrier gas (nitrogen), 0.6kg/cm² for the hydrogen, 0.6kg/cm² for make-up gas (nitrogen), and 0.5kg/cm² for the combustion air. Chromatograms were recorded with a computing integrator (Shimadzu Chromatopac C-R6A). Identification of sample FAs was made by comparing the relative retention times of standard FA methyl-esters, and the relative proportions were determined as percentages of summed peak areas.

The group of SFA consists of 12:0, 14:0, 15:0, 16:0, 17:0 18:0 and 20:0, while group of MUFA consists of 14:1 cis-9, 16:1 trans-9, 16:1 cis-9, 18:1 trans-11, 18:1 cis-9, and 22:1 cis-13. The group of PUFA includes n-6 PUFA (omega-6 PUFA, including 18:2cis-9,12, 18:3 cis-6,9,12, 20:3 cis-8,11,14, 20:4 cis-5,8,11,14, 22:4 cis-7,10,13,16) and n-3 PUFA (omega-3 PUFA, including 18:3 cis-9,12,15, 20:5 cis-5,8,11,14,17, 22:5 cis-7,10,13,16,19, 22:6 cis-4,7,10,13,16,19). Ratios of PUFA to SFA (P/S), MUFA to SFA (M/S) and n-6 PUFA to n-3 PUFA (n-6/n-3) were calculated. Attempts were conducted to develop better indices of the potential health attributes of foods containing a mixture of FAs with their indices of atherogenicity (IA) and thrombogenicity (IT) ^[12]. The mg FA of 100g meat was used to calculate the indices.

Ratios and indices were calculated individually of each beef sample before (raw) or after thermal treatment with different internal temperature. Mean differences of FAs from different lipid fractions were analyzed as a 2×3 factorial experimental design, by GLM-ANOVA model, with the factors of thermal treatment (boiling and microwave cooking) and terminal temperature (60°C, 70°C and 80°C), and using the raw meat data as a covariate. The statistical analysis was performed using SPSS 20.0.

3. Results and Discussion

Table 1. Changes in fatty acid composition (%) in the neutral lipid (NL) of beef (n = 10) ^†

Download as

PowerPoint Slide

Larger image(png format)

Tables index

Veiw figure

View current table in a new window

View next table

Table 2. Changes in fatty acid composition (%) in the polar lipid (PL) (n = 10) ^†

Download as

PowerPoint Slide

Larger image(png format)

Tables index

Veiw figure

View current table in a new window

View previous table

View next table

Fatty acids profiles changed differently between boiling and microwave cooking. There was no interaction (P < 0.05) between thermal treatment (boiling or microwave cooking) and terminal temperature (60°C, 70°C, and 80°C) of the main FA composition in NL (Table 1), PL (Table 2), and TL (Table 3). Briefly, in TL, boiling treatment affected 15:0, 18:1 cis-9, 18:2 cis-9,trans-11, 18:3 cis-6,9,12, 20:0, 20:3 cis-8,11,14, 22:4 cis-7,10,13,16, 22:6 cis-4,7,10,13,16,19 (Table 3) and M/S ratio (Table 4); whistle, terminal temperature affect the FA of 15:0, 16:1 cis-9, 17:1 cis-9, 18:2 cis-9,trans-11, 18:3 cis-6,9,12, 18:3 cis-9,12,15, 20:0, 20:3 cis-8,11,14, 20:5 cis-5,8,11,14,17, 22:1 cis-13, 22:4 cis-7,10,13,16, 22:5 cis-7,10,13,16,19, the group of MUFA, n-3 PUFA (Table 3) and ratio of n-6/n-3 (Table 4). However, thermal treatment or terminal temperature did not affect (P > 0.05) SFA, PUFA, n-6 PUFA, P/S, IA and IT index.

Table 3. Changes in fatty acid composition (%) in the total lipid (TL) (n = 10) ^†

Download as

PowerPoint Slide

Larger image(png format)

Tables index

Veiw figure

View current table in a new window

View previous table

View next table

Table 4. Changes in ratios and indices in the total lipid (TL) (n = 10) ^†

Download as

PowerPoint Slide

Larger image(png format)

Tables index

Veiw figure

View current table in a new window

View previous table

In FA composition of NL, percentage of total SFA did not change with boiling or microwave cooking. However, boiling or microwave cooking increased (P < 0.05) percentage of total SFA more than 6% in PL when heated to 80°C (Figure 1), which mainly caused by significant increase (P < 0.01) of 16:0 percentage. In TL, percentages of 16:0, 16:0 + 18:0 and total SFA were increased (P < 0.05) significantly after boiling and microwave cooking treatment. It was noted that SFA increased (P < 0.05) 9.09% in TL with boiling at the internal temperature of 80°C, while SFA only increased about 5% (P > 0.05) when internal temperature reached 60°C or 70°C. SFA increased (P < 0.05) 7%~9% in TL when beef microwave cooking to internal temperature from 60°C to 80 °C. It is suggested that beef overcooked (internal temperature ≥ 80°C) was not good for human health as SFA increased significantly.

Figure 1. Changes in SFA composition (%) in beef different fraction (NL, PL and TL) before (RAW) and after boiling (B) or microwave cooking (M)

Download as

PowerPoint Slide

Larger image(png format)

Figures index

Veiw figure

View current figure in a new window

View next figure

The MUFA composition of NL (Figure 2) was slightly reduced (P > 0.05) after the beef cooked to an internal temperature of 80°C compared with control, which mainly due to a reduction in 18:1cis-9 percentage. However, MUFA composition was increased (P > 0.05) conversely after the beef microwave heated compared with raw beef in NL. The MUFA composition of PL was reduced (P > 0.05) after the beef cooked to an internal temperature of 80°C. However, percentage of 18:1cis-9 was increased (P > 0.05) slightly with beef microwave cooking compared with raw, and percentage of 17:1cis-9 did not change (P > 0.05). These changes caused the MUFA of PL increased (P > 0.05) conversely after the beef microwave cooked compared with raw. The proportion of MUFA in TL (Figure 2) did not differ significantly (P > 0.05) after boiling. However, percentage of 18:1cis-9 was increased (P < 0.05) which caused the proportion of MUFA in TL increased (P < 0.05) with microwave cooking.

Figure 2. Changes in MUFA composition (%) in beef different fraction (NL, PL and TL) before (RAW) and after boiling (B) or microwave cooking (M)

Download as

PowerPoint Slide

Larger image(png format)

Figures index

Veiw figure

View current figure in a new window

View previous figure

View next figure

The fatty acids of PUFA, especially n-3 serial PUFA, reduces the risk of CHD ^[12], thus, changes of n-3 PUFA deserve particular attention during beef boiled or microwave cooked. In NL (Figure 3), total PUFA and n-6 PUFA composition increased (P < 0.05) after boiling to the internal temperature of 60°C or 80°C (mainly caused by increase of 18:2 cis-9,12 and 20:4 cis-5,8,11,14). Salcedo-Sandoval also found that cooked pork samples had higher concentrations of MUFAs and PUFAs (both n-3 and n-6) compared with raw products ^[31]. Stephen investigated the chemical changes involved during cooking (boiling), frying, canning and microwave heating of skipjack tuna (Katsuwonus pelamis), and found that the cholesterol content and the health beneficial n-3 PUFA of heat processed tuna fish were increased comparing with raw fish, thus recommended that boiling and microwave heating could be used to process tuna to retain n-3 fatty acids ^[37]. Composition of PUFA did not change (P > 0.05) after microwave cooking. Moreover, composition of n-3 PUFA was reduced (P < 0.05) with beef microwave heated in NL. In PL (Table 2), percentage of 18:3 cis-9,12,15 was reduced (P < 0.05), which caused total PUFA and n-3 PUFA composition reduced (P < 0.05) after boiling to the internal temperature of 70°C and 80°C. Compositions of total PUFA and n-3 PUFA did not change (P > 0.05) after microwave cooking in PL. Fatty acid of 20:3 cis-8,11,14 was not detected after microwave cooking in the PL fraction. In TL (Table 3), percentage of 18:2 cis-9,12 was slightly reduced (P > 0.05), however, 18:3 cis-9,12,15 and 20:4 cis-5,8,11,14 decreased with two thermal treatment. These changes caused total PUFA and n-3 PUFA compositions reduced (P < 0.05) in TL after the internal temperature of boiling or microwave cooking over 70°C.

Figure 3. Changes in total (a), n-3 (b), and n-6 (c) PUFA composition (%) in beef different fraction (NL, PL and TL) before (RAW) and after boiling (B) or microwave cooking (M)

Download as

PowerPoint Slide

Larger image(png format)

Figures index

Veiw figure

View current figure in a new window

View previous figure

PUFA had relatively lower melting points and were more susceptible to oxidation comparing with MUFA and SFA ^[32]. Intramuscular lipids were composed of the NL primarily consisting of triglycerides and the PL containing mostly phospholipids. The FA composition of the PL fraction contained a large proportion of PUFA. Polar lipids were known to be more susceptible to oxidation and the PUFA content of PL was the primary substrate of rancidity development. The PUFA in the PL exhibited similar susceptibility to thermal oxidation where cooking affected the PL to a greater extent than it does the NL. Intramuscular fat content was increased primarily through accumulation of FA in the NL ^[38]. An increase in beef intramuscular fat content in Longissimus lumborum beef steaks had been associated with increased flavor liking by consumers or flavor intensity rated by trained panelists ^{[32, 39]}.

The undesirable effects of dietary trans fatty acids (TFA) on human health had been reported^[40], but a distinction had often been made between trans FA from undesirable industrial sources and those that occurred naturally in food derived from animals such as milk and meat. TFA in diet from animal source were always considered acceptable ^{[41, 42]}. In current study, percentage of 18:1 trans-11 did not change (P > 0.05) with beef cooked to internal temperature of 60°C, 70°C and 80°C comparing with raw beef. However, with microwave cooking, percentage of 18:1 trans-11 was reduced (P < 0.05) in NL at internal temperature of 70°C and 80°C. However, percentage of 18:1 trans-11 was increased (P < 0.05) in PL at internal temperature of 80°C, which resulted in no changes (P > 0.05) in TL when microwave heated to internal temperature of 80°C.

Boiling reduced the unknown FAs in NL, but increased the unknown FAs in PL, which result in percentage of unknown FAs did not change in TL (Table 1-Table 3). However, microwave cooking reduced percentage of unknown FAs (< C16, C16 - C18, or > C18) significantly comparing with raw beef in NL, PL and TL.

Boiling or microwave cooking lean beef without external fat resulted in changes in the FA composition between the lipid fractions. The NL fraction represents the storage component of the lipid, whereas the PL fraction is the membrane component of the cell. Fatty acid compositions of the fractions differ greatly, with storage (neutral) lipids contained high composition of SFA ^[33] and MUFA ^[43] and PUFA located predominately in the membrane fraction ^[44]. Different distributions of FAs between storage and membrane fraction results in different responses with boiling ^[22] or microwave cooking ^[29] treatment. However, Smith, Savell ^[30] reported no changes in the FA changes of TL of beef steak after boiling, this mainly caused that only the TL fraction was investigated, therefore changes of FAs composition been overlooked.

The primary TFA in current study was trans vaccenic acid (18:1 trans-11), a precursor of the conjugated linoleic acid (18:2 cis-9 trans-11), for which there is evidence of desirable health effects ^[45]. Conjugated linoleic acids (CLA) are intermediates in the ruminal bio-hydrogenation, and appear in the lipid fractions of ruminant’s meat in higher concentrations than in non-ruminant meat. CLA had the potential to reduce the risk of cancer, CVD, diabetes, and obesity, as well as to boost the immune system ^[46]. Efforts had been made to increase amounts of PUFA in beef, particularly n−3 PUFA, which may have health benefits for consumers. Of the isomers of CLA, 18:2 cis-9,trans-11 was the most abundant FA in present experiment, which agreed with the conclusion of Rule, Broughton ^[47]. In storage lipid (NL), the percentages of 18:2 cis-9,trans-11 were less than 0.2% in raw and cooked beef, and not detected in beef with microwave cooking. However, 18:2 cis-9,trans-11 detected in raw, cooked and microwave heated beef membrane fraction (PL), and microwave cooking reduced (P < 0.01) percentage of 18:2 cis-9,trans-11 significantly in PL. It is considered that instant high energy microwave cooking changes the spatial structure of CLA and produces other FAs we did not identified. Fatty acid of 18:2 cis-9,trans-11 did not change (P > 0.05) with beef cooked to 60°C and 70°C in TL, these agreed with reports from Scheeder, Casutt ^[48] that CLA unchanged with beef cooked, however, 18:2 cis-9,trans-11 percentage decreased (P < 0.05) when cooked to internal temperature of 80°C in TL. Percentage of 18:2 cis-9,trans-11 decreased (P < 0.01) significantly with beef microwave cooking in TL.

The P/S ratios (0.58 ~ 0.75) in present experiment were higher than the recommended value (0.45) ^[49], which was desirable and good for health. P/S ratio decreased (P < 0.05) with beef cooked and microwave heated to the internal temperature of 70°C (0.62 vs. 0.75) in TL (Table 4). However, when the neutral and polar fractions were investigated, FAs change did not consistent as that of TL. PUFA of neutral fraction was increased (P < 0.05), while SFA did not change (P > 0.05) with beef boiled, which caused P/S ratio increased (P < 0.05) in storage (neutral) lipid. Conversely, P/S ratio of neutral fraction was slightly decreased (P > 0.05) with beef microwave cooked. In membranes (polar) lipid, SFA was increased (P < 0.05) with beef boiled or microwave cooked, which caused P/S ratio decreased slightly (P > 0.05). Thus, it was supposed that beef with intramuscular fat (marbling) affluent shall be treated with boiling as P/S ratio increase in storage lipid.

Although the consumers concerned about the health aspect, they also wanted a product that was highly palatable. The concentration of MUFAs (and specifically oleic acid) in beef was positively correlated with beef or beef fat flavors, indicating that as the concentration of oleic acid increases, so did beefy flavors. Therefore, increasing the M/S ratio would increase the palatability as well as the healthfulness of beef and beef products.^[50] However, both SFA and MUFA increased with beef boiling or microwave cooking comparing with raw in current study, which caused ratios of M/S did not change (P > 0.05) significantly in TL when internal temperature up to 70°C (Table 4).

Among n-3 PUFA, the nutritional importance of α-linolenic acid was unclear, since α-linolenic acid was not as bioactive as longer chain of n-3 FAs, such as eicosapentaenoic acid (EPA) and docosaesaenoic acid (DHA) ^[51]. The long chain n-3 PUFA, such as EPA (C20:5), DPA (C22:5) and DHA (C22:6) were widely recognized for their beneficial effects on health ^{[14, 15]}. Recommended intake by humans of n-6 FAs was suggested to be about 4% of dietary energy with a minimum of 1.5% and intake of n-3 FAs should be about 0.75% of dietary energy to avoid essential fatty acid (EFA) deficiency. Enser, Hallett ^[49] recommended that the n-6/n-3 PUFA value should be less than 4. In present research, n-6/n-3 PUFA value was of 6.72 in raw beef (Table 4) and increased with boiling and microwave cooking, and when the internal temperature reached 80°C, n-6/n-3 ratios increased (P < 0.01) significantly to 11.15 and 10.46 with boiling or microwave cooking.

The IA (index of atherogenicity) values of 0.32-0.42 in raw, boiled or microwave cooked beef in the present experiments (Table 4) were less than 0.70-0.72 reported by Ulbricht and Southgate ^[12] and 0.56-0.69 reported by Knight ^[52]. Value of IA increased (P < 0.05) from 0.32 to 0.40 or 0.42 at the internal temperature of 80°C with boiling or microwave cooking comparing with raw beef. Value of IT (index of thrombogenicity) increased (P < 0.05) stepwise when beef boiled or microwave cooked at the internal temperature of 60°C, 70°C and 80°C comparing with raw beef.

4. Conclusion

Fatty acids profiles changed with different thermal treatment (boiling or microwave cooking). Based on the above-mentioned results, it is proposed that beef with abundant intramuscular fat should be treated with boiling, as ratios of P/S increased with boiling comparing with microwave cooking in neutral lipid (mainly intramuscular fat) and the thermal treatment of microwave cooking decreased CLA content substantially. Beef was not recommended to be over-cooked (boiling or microwave cooking), the core temperature of beef should be around with 70°C as value of some indices linked with the potential health attributes of foods including n-6/n-3 PUFA, IA and IT increased significantly when beef internal temperature reaching 80°C compared with 70°C.

Acknowledgements

This research was supported by project from the State Administration of Grain in China (201313010), project from Jiangsu Education Dept. (13KJB550010), and project from the Priority Academic Program Development of Jiangsu higher education institutions (PAPD).

References

[1]	Realini, C.E., et al., Relative importance of cues underlying Spanish consumers’ beef choice and segmentation, and consumer liking of beef enriched with n-3 and CLA fatty acids. Food Quality and Preference, 2014. 33(0): p. 74-85.
	In article		CrossRef
[2]	Olmedilla-Alonso, B., F. Jiménez-Colmenero, and F.J. Sánchez-Muniz, Development and assessment of healthy properties of meat and meat products designed as functional foods. Meat Science, 2013. 95(4): p. 919-930.
	In article		CrossRef PubMed
[3]	Verbeke, W., et al., European citizen and consumer attitudes and preferences regarding beef and pork. Meat Science, 2010. 84(2): p. 284-292.
	In article		CrossRef PubMed
[4]	Feng, J., et al., Development and evaluation on a RFID-based traceability system for cattle/beef quality safety in China. Food Control, 2013. 31(2): p. 314-325.
	In article		CrossRef
[5]	Enser, M., et al., Fatty acid content and composition of english beef, lamb and pork at retail. Meat Science, 1996. 42(4): p. 443-456.
	In article		CrossRef
[6]	Matsumori, R., et al., High levels of very long-chain saturated fatty acid in erythrocytes correlates with atherogenic lipoprotein profiles in subjects with metabolic syndrome. Diabetes Research and Clinical Practice, 2013. 99(1): p. 12-18.
	In article		CrossRef PubMed
[7]	Mensink, R.P., Fatty Acids: Health Effects of Saturated Fatty Acids, in Encyclopedia of Human Nutrition (Third Edition), B. Caballero, Editor. 2013, Academic Press: Waltham. p. 215-219.
	In article		CrossRef
[8]	Ruiz-Núñez, B., et al., Saturated fatty acid (SFA) status and SFA intake exhibit different relations with serum total cholesterol and lipoprotein cholesterol: a mechanistic explanation centered around lifestyle-induced low-grade inflammation. The Journal of Nutritional Biochemistry, 2014. 25(3): p. 304-312.
	In article		CrossRef PubMed
[9]	Hoenselaar, R., Saturated fat and cardiovascular disease: The discrepancy between the scientific literature and dietary advice. Nutrition, 2012. 28(2): p. 118-123.
	In article		CrossRef PubMed
[10]	Hoenselaar, R., Re: More discrepancies around saturated fat and cardiovascular diseases. Nutrition, 2012. 28(11–12): p. 1206-1207.
	In article		CrossRef PubMed
[11]	Wood, K.E., et al., A low omega-6 polyunsaturated fatty acid (n-6 PUFA) diet increases omega-3 (n-3) long chain PUFA status in plasma phospholipids in humans. Prostaglandins, Leukotrienes and Essential Fatty Acids (PLEFA), 2014. 90(4): p. 133-138.
	In article		CrossRef PubMed
[12]	Ulbricht, T.L.V. and D.A.T. Southgate, Coronary heart disease: seven dietary factors. The Lancet, 1991. 338(8773): p. 985-992.
	In article		CrossRef
[13]	Scollan, N.D., et al., Enhancing the nutritional and health value of beef lipids and their relationship with meat quality. Meat Science, 2014. 97(3): p. 384-394.
	In article		CrossRef PubMed
[14]	Daley, C.A., Abbott, A., Doyle, P.S., Nader, G. A., & Larson, S., A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef. Nutrition Journal, 2010. 9: p. 10.
	In article		CrossRef PubMed
[15]	McAfee, A.J., et al., Red meat consumption: An overview of the risks and benefits. Meat Science, 2010. 84(1): p. 1-13.
	In article		CrossRef PubMed
[16]	Brugiapaglia, A., C. Lussiana, and G. Destefanis, Fatty acid profile and cholesterol content of beef at retail of Piemontese, Limousin and Friesian breeds. Meat Science, 2014. 96(1): p. 568-573.
	In article		CrossRef PubMed
[17]	Mourot, B.P., et al., Breeds and muscle types modulate performance of near-infrared reflectance spectroscopy to predict the fatty acid composition of bovine meat. Meat Science, 2015. 99(0): p. 104-112.
	In article		CrossRef PubMed
[18]	Ekine-Dzivenu, C., et al., Estimates of genetic parameters for fatty acids in brisket adipose tissue of Canadian commercial crossbred beef steers. Meat Science, 2014. 96(4): p. 1517-1526.
	In article		CrossRef PubMed
[19]	He, M.L., et al., Substitution of wheat dried distillers grains with solubles for barley silage and barley grain in a finishing diet increases polyunsaturated fatty acids including linoleic and alpha-linolenic acids in beef. Animal Feed Science and Technology, 2012. 175(3–4): p. 114-120.
	In article		CrossRef
[20]	Albertí, P., et al., Effect of including linseed in a concentrate fed to young bulls on intramuscular fatty acids and beef color. Meat Science, 2014. 96(3): p. 1258-1265.
	In article		CrossRef PubMed
[21]	Díaz, M.T., et al., Fatty acid composition of meat from typical lamb production systems of Spain, United Kingdom, Germany and Uruguay. Meat Science, 2005. 71(2): p. 256-263.
	In article		CrossRef PubMed
[22]	Duckett, S.K. and D.G. Wagner, Effect of Cooking on the Fatty Acid Composition of Beef Intramuscular Lipid. Journal of Food Composition and Analysis, 1998. 11(4): p. 357-362.
	In article		CrossRef
[23]	23.Sumnu, G., A review on microwave baking of foods. International Journal of Food Science & Technology, 2001. 36(2): p. 117-127.
	In article		CrossRef
[24]	Chandrasekaran, S., S. Ramanathan, and T. Basak, Microwave food processing—A review. Food Research International, 2013. 52(1): p. 243-261.
	In article		CrossRef
[25]	Vadivambal, R. and D.S. Jayas, Non-uniform Temperature Distribution During Microwave Heating of Food Materials—A Review. Food and Bioprocess Technology, 2010. 3(2): p. 161-171.
	In article		CrossRef
[26]	Gai, Q.-Y., et al., Microwave-assisted aqueous enzymatic extraction of oil from Isatis indigotica seeds and its evaluation of physicochemical properties, fatty acid compositions and antioxidant activities. Industrial Crops and Products, 2013. 45(0): p. 303-311.
	In article		CrossRef
[27]	Jiao, J., et al., Microwave-assisted aqueous enzymatic extraction of oil from pumpkin seeds and evaluation of its physicochemical properties, fatty acid compositions and antioxidant activities. Food Chemistry, 2014. 147(0): p. 17-24.
	In article		CrossRef PubMed
[28]	Garcı́a-Arias, M.T., et al., Cooking–freezing–reheating (CFR) of sardine (Sardina pilchardus) fillets. Effect of different cooking and reheating procedures on the proximate and fatty acid compositions. Food Chemistry, 2003. 83(3): p. 349-356.
	In article		CrossRef
[29]	Maranesi, M., et al., Effect of microwave cooking or broiling on selected nutrient contents, fatty acid patterns and true retention values in separable lean from lamb rib-loins, with emphasis on conjugated linoleic acid. Food Chemistry, 2005. 90(1–2): p. 207-218.
	In article		CrossRef
[30]	Smith, D.R., et al., Fatty acid and proximate composition of raw and cooked retail cuts of beef trimmed to different external fat levels. Meat Science, 1989. 26(4): p. 295-311.
	In article		CrossRef
[31]	Salcedo-Sandoval, L., et al., Effect of cooking method on the fatty acid content of reduced-fat and PUFA-enriched pork patties formulated with a konjac-based oil bulking system. Meat Science, 2014. 98(4): p. 795-803.
	In article		CrossRef PubMed
[32]	Legako, J.F., et al., Effects of USDA beef quality grade and cooking on fatty acid composition of neutral and polar lipid fractions. Meat Science, 2015. 100(0): p. 246-255.
	In article		CrossRef PubMed
[33]	Manner, W., R.J. Maxwell, and J.E. Williams, Effects of Dietary Regimen and Tissue Site on Bovine Fatty Acid Profiles. Journal of Animal Science, 1984. 59(1): p. 109-121.
	In article
[34]	Slover, H.T. and E. Lanza, Quantitative analysis of food fatty acids by capillary gas chromatography. Journal of the American Oil Chemists’ Society, 1979. 56(12): p. 933-943.
	In article		CrossRef
[35]	Maxwell, R.J. and W.N. Marmer, Systematic protocol for the accumulation of fatty acid data from multiple tissue samples: tissue handling, lipid extraction and class separation, and capillary gas chromatographic analysis. Lipids, 1983. 18(7): p. 453-9.
	In article		CrossRef PubMed
[36]	AOCS, Fats, Oils and Lipid Related Analytical Methods Official Method Ce 1b-89. 5th ed ed. 2001, Illinois: Champaign.
	In article
[37]	Stephen, N., et al., Effect of different types of heat processing on chemical changes in tuna. Journal of Food Science and Technology, 2010. 47(2): p. 174-181.
	In article		CrossRef PubMed
[38]	Wood, J.D., et al., Fat deposition, fatty acid composition and meat quality: A review. Meat Science, 2008. 78(4): p. 343-358.
	In article		CrossRef PubMed
[39]	Hunt, M.R., et al., Consumer assessment of beef palatability from four beef muscles from USDA Choice and Select graded carcasses. Meat Science, 2014. 98(1): p. 1-8.
	In article		CrossRef PubMed
[40]	Chowdhury, R., et al., Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med, 2014. 160(6): p. 398-406.
	In article		CrossRef PubMed
[41]	Jacome-Sosa, M.M., et al., Diets enriched in trans-11 vaccenic acid alleviate ectopic lipid accumulation in a rat model of NAFLD and metabolic syndrome. Journal of Nutritional Biochemistry. 25(7): p. 692-701.
	In article		CrossRef PubMed
[42]	Purchas, R.W., et al., A comparison of the trans fatty acid content of uncooked and cooked lean meat, edible offal and adipose tissue from New Zealand beef and lamb. Journal of Food Composition and Analysis, 2015. 41(0): p. 151-156.
	In article		CrossRef
[43]	Sturdivant, C.A., et al., Fatty acid composition of subcutaneous and intramuscular adipose tissues and M. longissimus dorsi of Wagyu cattle. Meat Science, 1992. 32(4): p. 449-458.
	In article		CrossRef
[44]	Sweeten, M.K., Cross, H.R., Smith, G.C. and Smith, S.B., Subcellular Distribution and Composition of Lipids in Muscle and Adipose Tissues. Journal of Food Science, 1990. 55: p. 43–45.
	In article		CrossRef
[45]	Dilzer, A. and Y. Park, Implication of Conjugated Linoleic Acid (CLA) in Human Health. Critical Reviews in Food Science and Nutrition, 2012. 52(6): p. 488-513.
	In article		CrossRef PubMed
[46]	Kallas, Z., C.E. Realini, and J.M. Gil, Health information impact on the relative importance of beef attributes including its enrichment with polyunsaturated fatty acids (omega-3 and conjugated linoleic acid). Meat Science, 2014. 97(4): p. 497-503.
	In article		CrossRef PubMed
[47]	Rule, D.C., et al., Comparison of muscle fatty acid profiles and cholesterol concentrations of bison, beef cattle, elk, and chicken. J Anim Sci, 2002. 80(5): p. 1202-11.
	In article		PubMed
[48]	Scheeder, M.R.L., et al., Fatty acid composition, cooking loss and texture of beef patties from meat of bulls fed different fats. Meat Science, 2001. 58(3): p. 321-328.
	In article		CrossRef
[49]	Enser, M., et al., Fatty acid content and composition of UK beef and lamb muscle in relation to production system and implications for human nutrition. Meat Science, 1998. 49(3): p. 329-341.
	In article		CrossRef
[50]	Blackmon, T., et al., Ground beef patties prepared from brisket, flank and plate have unique fatty acid and sensory characteristics. Meat Science, 2015. 103(0): p. 46-53.
	In article		CrossRef PubMed
[51]	Decker, E.A. and Y. Park, Healthier meat products as functional foods. Meat Science, 2010. 86(1): p. 49-55.
	In article		CrossRef PubMed
[52]	Knight, T.W., et al., Factors affecting the variation in fatty acid concentrations in lean beef from grass‐fed cattle in New Zealand and the implications for human health. New Zealand Journal of Agricultural Research, 2003. 46(2): p. 83-95.
	In article		CrossRef