Effect of dietary conjugated linoleic acid in combination with monounsaturated fatty acids on the meat composition and quality traits of dry-cured loin

Three levels (0%, 1% and 2%) of an enriched conjugated linoleic acid oil (CLA) were combined with two levels of monounsaturated fatty acids (MUFA) (low −19% average and high −39% average) for pig feeding. Composition, weight losses, lipid oxidation (thiobarbituric acid test, TBARs), change in the fatty acid content of the lipid fractions and sensory analysis of dry-cured loin as affected by dietary CLA, MUFA and CLA × MUFA interaction were studied. CLA and CLA × MUFA did not affect moisture and intramuscular fat content of dry-cured loin, weight losses during the processing, changes in the content of most fatty acids from lipid fractions and sensory traits. CLA and MUFA supplementation led to lower TBARs values (1.3 mg MDA/kg sample for 0% CLA and 0.9 mg MDA/kg sample for 2% CLA; 1.2 mg MDA/kg sample for low MUFA diets and 0.9 mg MDA/kg sample for high MUFA diets), the highest TBARs values being detected for 0% CLA-low MUFA diets [1.5 mg MDA/kg sample]. The combination of dietary CLA with different MUFA levels in pig diets did not affect most composition and quality traits of dry-cured loin. Dietary CLA and MUFA seemed to lead to lower lipid oxidation in this product.     

Oxidative changes of fresh loin from pig,caused by dietary conjugated linoleic acid and monounsaturated fatty acids,during refrigerated storage

Three levels (0%, 1% and 2%) of a conjugated linoleic acid enriched oil (CLA) were combined with two levels of monounsaturated fatty acids (MUFA) (19% and 39% average) for pig feeding. Changes in instrumental colour, lipid oxidation (thiobarbituric acid reactive substances, TBARS) and volatile profile of fresh loin chops, as affected by dietary CLA, MUFA and CLA × MUFA, were studied throughout 7 days of refrigerated storage. Lightness (L∗) evolution was conditioned by dietary CLA, whereas changes in redness (a∗) and yellowness (b∗) were unaffected by dietary supplements. Dietary CLA at 2% led to higher TBARS values of loin chops at day 7 of refrigerated storage (p < 0.05), while MUFA supplementation and CLA × MUFA interaction did not affect lipid oxidation. Dietary CLA, MUFA or CLA × MUFA did not affect most volatile compounds of loin chops after 7 days of storage.     

Volatile compounds of fresh and dry-cured loin as affected by dietary conjugated linoleic acid and monounsaturated fatty acids

Three levels (0%, 1% and 2%) of an enriched conjugated linoleic acid oil (CLA) were combined with two levels of monounsaturated fatty acids (MUFA) (low (19%) average and high (39%) average) for pig feeding. The profile of volatile compounds of fresh and dry-cured loin as affected by dietary CLA, MUFA and CLA × MUFA interaction was studied by headspace-solid phase microextraction coupled to gas chromatography–mass spectrometry. A total of 27 and 69 compounds were identified in fresh loin and dry-cured loin, respectively. Identified compounds were alcohols, aldehydes, aliphatic hydrocarbons, aromatic hydrocarbons, esters, furans, ketones, nitrogen compounds, sulphur compounds and terpenes. No qualitative differences in volatile compounds caused by the assayed treatments were found neither in fresh loin nor in dry-cured loin. Dietary CLA, MUFA and their interaction did not affect the level of most detected volatiles. Nevertheless, in fresh loin, the level of heptanal significantly increased due to dietary CLA (p = 0.001) and the area units (AU) for ethyl benzene and 1,3-dimethyl benzene increased at 1% CLA (p < 0.05). In the case of dry-cured loin, the AU of heptanal, nonanal and 2-nonenal contents increased due to dietary CLA (p = 0.016, 0.024 and 0.019, respectively).     

Effect of cooking methods on fatty acids,conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat

The effect of boiling, microwaving and grilling on the composition and nutritional quality of beef intramuscular fat from cattle fed with two diets was investigated. Longissimus lumborum muscle from 15 Alentejano young bulls fed on concentrate or pasture was analyzed. Cooking losses and, consequently, total lipids, increased directly with the cooking time and internal temperature reached by meat (microwaving > boiling > grilling). The major changes in fatty acid composition, which implicated 16 out of 34 fatty acids, resulted in higher percentages in cooked beef of SFA and MUFA and lower proportions of PUFA, relative to raw meat, while conjugated linoleic acid (CLA) isomers revealed a great stability to thermal processes. Heating decreased the PUFA/SFA ratio of meat but did not change its n−6/n−3 index. Thermal procedures induced only slight oxidative changes in meat immediately after treatment but hardly affected the true retention values of its individual fatty acids (72–168%), including CLA isomers (81–128%).     

Volatile compounds of experimental liver pâté from pigs fed conjugated linoleic acid in combination with monounsaturated fatty acids

BACKGROUND: Feeding conjugated linoleic acid (CLA) to pigs leads to CLA‐enriched meat products, which are of current interest owing to the potential health properties of CLA. However, dietary CLA increases the ratio of saturated to monounsaturated fatty acids (MUFA) in pig tissues. Combining CLA with high MUFA levels in pig diets may counteract this effect. Owing to the modification of fatty acid composition, variation in the volatile profile of derived meat products might be expected. The aim of the present work was to study the volatile profile, and its change during storage, of experimental liver pâté manufactured from pigs fed different levels of CLA and MUFA. RESULTS: Regardless of the CLA or MUFA level, 98 compounds were identified. Lower area units were observed for most branched aldehydes, ketones and alcohols and some furans, sulfur compounds and nitrogen compounds with increasing CLA and MUFA contents. Levels of nonanal, propan‐2‐one, dodecane, 2‐pentylfuran and ethylbenzene were higher in CLA pâtes. The effect of experimental diets on the change in volatiles during storage was not significant. CONCLUSION: Supplementation of pig diets with CLA isomers in combination with low or high MUFA levels seems to have a significant effect on the volatile profile of pork liver pâté. Copyright © 2009 Society of Chemical Industry     

Fatty acid profile,carcass and meat quality traits of young Nellore bulls fed crude glycerin replacing energy sources in the concentrate

Carcass and meat quality traits of 60 Nellore young bulls fed diets without crude glycerin (CG); with CG replacing corn (CGc; 10% of dry matter — DM) in the concentrate; and with CG replacing soybean hull (CGsh; 10% of DM) in the concentrate were evaluated. Diets were evaluated at two concentrate levels (CLs). The CL did not affect cold carcass weight (CCW; P = 0.6074), cold carcass dressing (CCD; P = 0.9636), rib fat thickness (RFT; P = 0.8696) and longissimus muscle area (LMA; P = 0.7524). Animals fed diets with CGc or CGsh showed meat with greater deposition of monounsaturated fatty acid (MUFA; P = 0.0022) and CLA (18:2 cis-9, trans-11) contents (P = 0.0001) than animals fed diets without CG. The inclusion of 10% of CG in diets CGc or CGsh does not affect the carcass and meat quality traits; however, it increases the MUFA and CLA contents in beef, although these changes are very small in nutritional terms.     

Influence of the type of forage supplied to ewes in pre- and post-partum periods on the meat fatty acids of suckling lambs

The aim of this study was to evaluate the use of forage diets (grazing vs. hay) around the time of ewe parturition, on the fatty acids profile of suckling lamb meat (10-12 kg body weight). Forty-eight multiparous single-bearing ewes were used. The experimental treatments were conducted during the last 5 weeks of pregnancy and the 5 weeks of lactation in a 2 × 2 factorial design. Ewes were fed ad libitum on pastures or hay in the autumn. Results showed that milk from grazing ewes during the pre-partum period had a higher content of PUFA and CLA (P < 0.05) and VA, CLA in their suckling lambs' meat (P < 0.05). The effect in post-partum feeding was greater, revealing higher CLA, PUFA/SFA, PUFA n-3 and PUFA n-6/n-3 in milk and meat (P < 0.05). The CLA, VA and PUFA n-6/n-3 ratios are those that are most affected by grazing. Pre-partum grazing, regardless of post-partum feeding, improves FA composition, increasing CLA content in both milk and meat.     

Effect of different cooking methods on lipid oxidation and formation of volatile compounds in foal meat

The influence of four different cooking methods (roasting, grilling, microwaving and frying) on cooking loss, lipid oxidation and volatile profile of foal meat was studied. Cooking loss were significantly (P < 0.001) affected by thermal treatment, being higher (32.5%) after microwaving and lower after grilling (22.5%) and frying (23.8%). As expected, all the cooking methods increased TBARs content, since high temperature during cooking causes increased oxidation in foal steaks, this increase was significantly (P < 0.001) higher when foal steaks were microwaved or roasted.     

Effect of different temperature–time combinations on physicochemical,microbiological, textural and structural features of sous-vide cooked lamb loins

Lamb loins were subjected to sous-vide cooking at different combinations of temperature (60, 70, and 80 °C) and time (6, 12, and 24 h). Different physicochemical, histological and structural parameters were studied. Increasing cooking temperatures led to higher weight losses and lower moisture contents, whereas the effect of cooking time on these variables was limited. Samples cooked at 60 °C showed the highest lightness and redness, while increasing cooking temperature and cooking time produced higher yellowness values. Most textural variables in a texture profile analysis showed a marked interaction between cooking temperature and time. Samples cooked for 24 h showed significantly lower values for most of the studied textural parameters for all the temperatures considered. Connective tissue granulation at 60 °C and gelation at 70 °C were observed in the SEM micrographs. The sous-vide cooking of lamb loins dramatically reduced microbial population even with the less intense heat treatment studied (60 °C–6 h).     

Relationship between the solubility,dosage and antioxidant capacity of carnosic acid in raw and cooked ground buffalo meat patties and chicken patties

Antioxidant capacity of oil soluble and water dispersible carnosic acid (CA) extracted from dried rosemary leaves using HPLC was evaluated at two different dosages (22.5 ppm vs 130 ppm) in raw and cooked ground buffalo meat patties and chicken patties. Irrespective of total phenolic content, CA extracts reduced (p < 0.05) the thiobarbituric acid reactive substances (TBARS) by 39%–47% and 37%–40% in cooked buffalo meat and chicken patties at lower dosage (22.5 ppm) relative to control samples. However, at higher dosage (130 ppm) the TBARS values were reduced (p < 0.05) by 86%–96% and 78%–87% in cooked buffalo meat and chicken patties compared to controls. The CA extracts were also effective in inhibiting (p < 0.05) peroxide value and free fatty acids in cooked buffalo meat and chicken patties. The CA extracts when used at higher dosage, were also effective in stabilizing raw buffalo meat color.     

Chemical characteristics,fatty acid composition and conjugated linoleic acid (CLA) content of traditional Greek yogurts

Many studies with conjugated linoleic acid (CLA) indicate that it has a protective effect against mammary cancer. Because dairy products are the most important dietary sources of CLA, we have investigated the CLA concentrations and additionally the fatty acid profiles and chemical composition of several commercial, traditional, Greek yogurts from different geographical origin. The fat content of yogurts was in the order of goat < cow < sheep. Cow, sheep and goat milk yogurts contain respectively 0.128–1.501, 0.405–1.250 and 0.433–0.976 g CLA/100 g fat. Low-fat milk yogurts showed lower values of c-9, t-11 CLA content on lipid basis compared to full-fat yogurts. Samples from mountain areas showed average c-9, t-11 CLA content higher than those from prairie districts. The highest amounts of saturated fatty acids (SFA) were found in low-fat yogurts, of monounsaturated fatty acids (MUFA) in sheep milk yogurts and of polyunsaturated fatty acid (PUFA) in low-fat cow milk yogurts.     

Effect of cooking on the capsaicinoids and phenolics contents of Mexican peppers

Raw and cooked (boiled and grilled) Poblano, Bell, Chilaca, Caribe, Jalapeño, Serrano, Habanero, and Manzano peppers were evaluated for tristimulus colour, capsaicinoids (capsaicin, dihydrocapsaicin, nordihydrocapscapsaicin), and total phenolic contents. Boiling (96 °C) and grilling (210 °C) was performed under household conditions according to typical procedures of the Mexican cuisine. Contents of capsaicin (0.6–913.8 μg/g), dihydrocapsaicin (0–756.9 μg/g), nordihydrocapsaicin (0–68.2 μg/g), and total phenolics (1150.5–2190.0 μg of gallic acid equivalents/g) in raw peppers varied widely between types of peppers. Moderate losses (1.1–28.1%) in capsaicinoids were induced by boiling while grilling caused a significant increase (2.6–924.9%) in the content of these compounds. Proportion of individual capsaicinoids was similar in raw and cooked peppers. Boiling and grilling sequentially increased (7.4–137.0%) the total phenolic content in pungent peppers. Total phenolic content in non-pungent Bell peppers was reduced by cooking (1.6–26.9%). Boiling induced smaller changes in colour values (L*, a*, and b*) compared to grilling. The results demonstrated that Mexican raw peppers are rich in capsaicinoids and phenolic compounds. Household cooking can cause either decreases or increases in the content of such compounds in peppers.     

Cooking effect on fatty acid profile of pork breakfast sausages enriched in conjugated linoleic acid by dietary supplementation or direct addition

The effectiveness of increasing CLA in pork products through animal dietary supplementation or direct addition in the product formulation has been studied, and the effect of grilling on dry matter and fat contents and fatty acid composition has been analysed. Sausages made with meat and back fat from pigs with CLA dietary supplementation had the highest saturated fatty acid content. Sausages from dietary supplementation and direct addition had CLA levels between 6% and 7% of total fatty acids. Moisture and fat contents decreased and increased respectively after cooking for the three sausage types (control, dietary supplementation, direct addition). Grilling had little effect on fatty acid levels, especially for sausages with direct addition in the product formulation. In general, saturated fatty acids increased and poly-unsaturated fatty acids decreased due to the increase of C16:0 and to the decrease of C18:2 n − 6c and C18:3 n − 3 fatty acids. Added CLA, both from animal dietary supplementation or direct addition, remained at similar levels in cooked sausages to those found in raw sausages.     

The effect of seasonality of the growing–finishing period on carcass,meat and fat characteristics of heavy barrows and gilts

A trial was conducted to study the effect of gender (barrows; gilts) and seasonality of growing–finishing period (S, summer; W, winter) on the carcass and meat characteristics and fatty acid (FA) profile of subcutaneous fat of pigs slaughtered at 131 kg of body weight. No significant gender × seasonality interaction was detected and the differences between genders were scarce. The S pigs had a 13.2% thinner fat depth over the Gluteus medius muscle and a higher yield of shoulders and loins by 10.6% and 10.0%, respectively than W pigs. Meat from S pigs had 32.5% lower intramuscular fat content and higher cooking losses (9.1%) and shear force (6.4%) than meat from W pigs. Subcutaneous fat from S pigs had a 7.8% higher percentage of saturated FA and 4.9% lower monounsaturated FA than that from W pigs. It is concluded that in Spanish natural-environment facilities, the seasonality of the growing–finishing period affects the carcass, and meat and fat quality of heavy pigs.     

Flavour differences of cooked longissimus muscle from Chinese indigenous pig breeds and hybrid pig breed (Duroc × Landrace × Large White)

The objectives of this study were to investigate the flavour quality and volatile aroma compounds of cooked longissimus muscle from five typical Chinese indigenous pig breeds: Lantang (LT), Dahuabai (HB), Laiwu (LW), Rongchang (RC), Tongcheng (TC) and typical hybrid pig breed Duroc × Landrace × Large White (DLW). The chemical compositions of the main meat flavour precursors of the longissimus muscle from all six breeds were also examined. Distinct differences in amino acid composition and fatty acid composition of longissimus muscle, between the breeds, were observed. Among all six breeds, LW and RC had the highest intramuscular fat content and the lowest crude protein content; DLW had the lowest longissimus muscle fat content and the highest crude protein content. One-way analysis of variance showed that 23 volatile compounds were significantly affected by breed. Sensory analysis indicated that cooked longissimus muscle from DLW had the lowest pork flavour intensity and flavour-liking, compared with the Chinese indigenous breeds. LW and HB showed the highest pork flavour intensity and flavour-liking in cooked longissimus muscle.     

Electrical conductivity changes of minced beef–fat blends during ohmic cooking

Minced beef–fat blends having different fat level (2%, 9% and 15%) and full meat-fat samples were ohmically cooked by different voltage gradients (20, 30 and 40 V/cm). Main factors affecting the electrical conductivity were the temperature and the composition of the blends. Although the effect of initial fat content on electrical conductivity was statistically significant, voltage gradient did not affect the electrical conductivity changes during cooking treatment (p > 0.05). The electrical conductivity of the samples increased with increasing temperature up to the critical initial cooking temperature (60–70 °C) depending on the fat level, and then decreased due to structural changes and the increase in the bound water during cooking. The results of the nonlinear mathematical model including the effects of initial fat level and the temperature on the electrical conductivity changes had good agreement (r = 0.952; SEM = 0.009) with the experimental data. The determination of electrical conductivity changes being affected by process variables is crucial to characterize the ohmic cooking of meat products and design of ohmic systems.     

Preliminary investigation on the relationship of Raman spectra of sheep meat with shear force and cooking loss

A prototype handheld Raman system was used as a rapid non-invasive optical device to measure raw sheep meat to estimate cooked meat tenderness and cooking loss. Raman measurements were conducted on m. longissimus thoracis et lumborum samples from two sheep flocks from two different origins which had been aged for five days at 3–4 °C before deep freezing and further analysis. The Raman data of 140 samples were correlated with shear force and cooking loss data using PLS regression. Both sample origins could be discriminated and separate correlation models yielded better correlations than the joint correlation model. For shear force, R² = 0.79 and R² = 0.86 were obtained for the two sites. Results for cooking loss were comparable: separate models yielded R² = 0.79 and R² = 0.83 for the two sites. The results show the potential usefulness of Raman spectra which can be recorded during meat processing for the prediction of quality traits such as tenderness and cooking loss.     

Evaluation of the effects of selected plant-derived nutraceuticals on the quality and shelf-life stability of raw and cooked pork sausages

The effect of lutein (200 μg/g meat), sesamol (250 μg/g meat), ellagic acid (300 μg/g meat) and olive leaf extract (200 μg/g meat) on total viable counts (TVC), pH, water holding capacity (WHC), cooking loss, lipid oxidation (thiobarbituric acid-reactive substances, TBARs), colour stability, texture and sensory evaluation of fresh and cooked pork sausages stored in aerobic or modified atmosphere packs (MAP) was investigated. Addition of sesamol, ellagic acid and olive leaf extract reduced (P < 0.001) lipid oxidation in all packaged raw and cooked pork sausages. Antioxidant potency followed the order: sesamol 250 > ellagic acid 300 > olive leaf extract 200 > lutein 200 for both raw and cooked pork sausages. Addition of sesamol increased (P < 0.001) WHC on days 2 and 12 of MAP storage. Meat addition of lutein, sesamol, ellagic acid and olive leaf extract had no detrimental effect on pH, cooking losses, TVCs, tenderness, juiciness, texture or product flavour. Lutein, sesamol, ellagic acid and olive leaf extract were effective as natural functional ingredients in suppressing lipid oxidation and have the potential to be incorporated into functional raw and cooked pork sausages.     

Ohmic cooking of ground beef: Effects on quality

Conventional cooking tends to be slow and the surface of the food always receives a much more severe heating treatment than the rest of the food. Ohmic heating has the potential to be much faster and produces even more cooking. In this work cylindrical ground beef samples having different initial fat contents (2%, 9% and 15%) were cooked ohmically (20, 30 and 40 V/cm) and conventionally. Ohmic cooking was faster than the conventional cooking (p < 0.05). Ohmically cooked samples were firmer than those conventionally cooked but yield and fat retention was similar. However, the reduction in volume during cooking was significantly smaller from 5.36% to 6.97% in ohmic cooking than the conventional system which was measured from 26.01 to 31.59. The voltage gradient applied during ohmic cooking was not related to the quality of the cooked meat. These results show that ohmic cooking could be a fast-alternative method for meat products.     

Trans-18:1 and conjugated linoleic acid profiles after the inclusion of buffer,sodium sesquicarbonate,in the concentrate of finishing steers

Ninety-six European crossbred steers were fed a barley-based finishing diet for differing lengths of time (34–104 days) to investigate if adding dietary buffer (sodium sesquicarbonate at 1.5% as fed) could improve the trans-18:1 (GC-FID) and CLA (Ag⁺-HPLC-DAD) content and isomeric profile of beef produced. Results indicate that the addition of buffer to diets of cattle fed high concentrate diets has limited effects on the overall fatty acid composition of backfat and muscle tissues. However, buffer addition can help to prevent a 10t- shift by maintaining a better (higher) 11t-/10t-18:1 ratio in both meat and backfat during the first 30–60 days of feeding a high grain diet. Over time, however, the effect is lost becoming equal in tissues from animals with or without buffer addition to their diets.