Evaluation of E-beam irradiation and storage time in pork exudates using NMR metabolomics.

Seventy-two exudates from pork tenderloin samples, subjected to E-beam irradiation treatments, have been employed to monitor, through 1H NMR analysis, the effects of irradiation dose (0, 1, 2 and 6 kGy) and storage time (1, 6 and 12 days). As far as we know, this is the first study where meat exudate is employed to monitor the effects of irradiation dose and storage time. The 1H NMR spectra, obtained after ~ 2 min, allowed to determine the main components of the pork exudate. Results show that 1H NMR-based metabolomics provides valuable information about the metabolic changes suffered during storage and how these transformations could be affected by E-beam irradiation treatment. The ease to obtain exudates, the simple NMR sample preparation, the good correlation between the selected metabolites, the irradiation treatment and the storage times point to that this study could be the first step to develop a new method for analysis and control of meat conservation and to evaluate its irradiation treatment.

Use of MRI as a predictive tool for physicochemical and rheologycal features during cured ham manufacturing.

Magnetic resonance imaging (MRI) was used to study the structural changes during dry-cured ham manufacturing. T1, T2 and apparent diffusion coefficient (ADC) were determined. Dry cured hams were analysed at different steps of the manufacturing process (raw, salted, post salted, half-cured and cured). Structural changes were linked with the rheological behaviour, estimated by texture profile analysis (TPA) performed in three different muscles of hams (semimembranosus, semitendinosus and biceps femoris). A decrease for T1, T2 and ADC parameters during the curing process was observed, connected to the dehydration kinetics and salt diffusion. Curing process increased hardness and chewiness and reduced elasticity and cohesiveness. Mathematical models were defined to obtain useful equations to monitor ripening. Multiple and simple linear regression models were performed to predict water and salt content and rheological features evolution through MRI parameters. Best settings were achieved with water and salt content for the three studied muscles (R2 around 0.90). T1, T2 and ADC showed a negative correlation with hardness and a positive relation with springiness and cohesiveness.

Effect of sex, dietary glycerol or dietary fat during late fattening, on fatty acid composition and positional distribution of fatty acids within the triglyceride in pigs.

The effect of sex, source of saturated fat (lard v. palm oil) and glycerol inclusion in the fattening diet on composition and fatty acid positional distribution in the triglyceride molecule was studied in pigs from 78 to 110 kg BW. Average daily gain and carcass characteristics, including ham and loin weight, were not affected by dietary treatment but sex affected backfat depth (P < 0.01). A significant interaction between sex and glycerol inclusion was observed; dietary glycerol increased lean content in gilts but not in barrows (P < 0.05 for the interaction). Individual and total saturated fatty acid (SFA) concentrations were greater in barrows than in gilts. In contrast, the concentration of total polyunsaturated fatty acids (PUFA) and of C18:2n-6, C18:3n-3, C20:3n-9 and C20:4n-6 in the intramuscular fat (IMF) was higher (P < 0.05) in gilts than in barrows. Sex did not affect total monounsaturated fatty acids (MUFA) concentration in the IMF. The proportion of SFA in the subcutaneous fat (SF) was higher in barrows than in gilts (P < 0.001). Within the individual SFA, sex affected only the concentrations of C14:0 and C16:0 (P < 0.001). Dietary fat did not affect total SFA or PUFA concentrations of the IMF but the subcutaneous total MUFA concentration tended to be higher (P = 0.079) in pigs fed lard than in pigs fed palm oil. Dietary glycerol increased total MUFA and C18:1n-9 concentration in the IMF and increased total MUFA and decreased C18:2n-6, C18:3n-3 and total PUFA concentrations in the SF. The data indicate that altering the fatty acid composition of the triglyceride molecule at the 2-position, by dietary intervention during the fattening phase, is very limited.

Effect of fatty acid composition and positional distribution within the triglyceride on selected physical properties of dry-cured ham subcutaneous fat.

Analysis of fatty acid (FA) positional distribution within the triglyceride (TG) and selected physical properties of dry-cured ham subcutaneous fat (SF) were carried out. The slip point (SP) of the SF was related to the concentration and positional distribution of FA. When C16:0 was in Sn-2, the SP depended on the FA present in Sn-1,3. Hardness was related to the FA concentration in external positions of TG. A significant direct linear correlation between hardness against C18:0, SFA and average chain length (ACL) and inverse against C18:1, C18:2 and PUFA and unsaturation index (UI) in external positions was found. Adhesiveness was related to SFA, C16:0, C18:0, C18:1, MUFA, UI and ACL exclusively in Sn-2 position. A different role of FA in Sn-2 and Sn-1,3 positions on SP and texture properties of fat was found.

Alternative method for intramuscular fat analysis using common laboratory equipment.

A procedure to quantify intramuscular fat was developed using common inexpensive laboratory equipment. Three homogenization methods of lyophilized muscle samples (Ball-mill, Grinder and Mortar) and two extraction methods (Ball-mill or Vortex) were used in turkey meat and pork. Two-hundred mg of lyophilized and homogenized samples were accurately weighed and mixed with 1.5 mL of dichloromethane-methanol (8:2) and shaken either in a Mixer Mill (MM400, Retsch Technology) or in a Vortex. The final mixture was separated by centrifugation. Solvent was evaporated under a nitrogen stream and lipid content was gravimetrically determined. Besides, it was checked that the fatty acid profile was not altered by the protocol used. Moreover, the analysis of 4 replicas from the same sample showed different variation coefficients (16-29%) for the new procedures proposed over a wide range of IMF content. The combination of Grinder and Vortex methodologies can be proposed as a simple and inexpensive alternative to previous ones.

The suitability of plasma powder for cold-set binding of pork and restructured dry ham.

To determine the ability of cold-set binder plasma powder (PP) for manufacturing restructured deboned dry ham, the effect of meat pre-treatment and PP preparation on the binding rate (k) and maximum binding force (BFmax) of pork model systems and deboned ham were evaluated. In pork model systems, the highest values for k (about 0.4Ncm(-2)h(-1)) and BFmax (about 2.5Ncm(-2)) were obtained when powder or rehydrated plasma [in water or in NaCl aqueous solution at 0.5%] was applied onto the meat surface without additional pre-treatment or prior immersion in saline aqueous solution. Similar meat pre-treatment and PP preparation were used to restructure fresh deboned leg resulting in stable meat binding performances during salting and drying. An important increase in the binding force (BFmax>10Ncm(-2)) occurred over the drying period (after 4weeks). Scanning electron microscopy showed different morphologies of the binding area, mainly depending on whether powder or rehydrated plasma was used.

Dry-cured ham restructured with fibrin.

The viability of a fibrinogen-thrombin system (FT) to bind fresh deboned hams for incorporation in the salting and ripening processes, to produce cured ham, was studied. The effects of the different processing variables (pH, NaCl concentration, temperature and gelation time) on FT, a meat emulsion mixed with FT, fresh pork portions and deboned hams restructured with FT were analyzed. The most stable and firmest fibrin gels were obtained after 6h of adding the FT, with less than 2% NaCl and pH 7-8.4. Scanning electron microscopy of the fibrin gel showed fibrillar structures with a high degree of cross-linking and a high density. Two structures were found in the binding area of restructured meat; one in the central part with similar characteristics to fibrin gels and, another in the area of contact between the meat surfaces, where a filamentous structure connected the fibrin gels with the muscle bundles.

Use of e-beam for shelf-life extension and sanitizing of marinated pork loin.

The effectiveness of E-beam radiation to extend the shelf-life of marinated pork loin slices stored at 4 and 8°C (temperature abuse) has been studied. The shelf-life was extended from 7 to 16 and >20 days after the application of 1 and 2 kGy, respectively. In the event of a temperature abuse occuring during the product distribution (e.g., increase to 8°C), the shelf-life would be extended from 5 to 10 and 16 days, respectively, when applying the doses mentioned previously. From a public health point of view, the irradiation of marinated pork loin may be marketable for a longer period of time of up to two weeks, and guarantees a practically Salmonella and Listeria-free product. Minor changes are produced by the E-beam treatment in the main sensory and rheological characteristics. The odor was the most affected feature, but the off-odors diminished with increased storage. In any case, testers judged the samples to be adequate for marketing.

Lack of growth of Listeria monocytogenes and Staphylococcus aureus in temperature abuse of E-beam treated ready-to-eat (RTE) cooked ham.

The behaviour of Listeria monocytogenes and Staphylococcus aureus in vacuum-packed cooked ham slices treated with an electron beam and stored at 4, 7 and 10 degrees C was investigated. Cooked ham slices were inoculated with L. monocytogenes and S. aureus and electron beam treated at 2 and 3 kGy. After treatment, a long temperature-dependent death phase was observed, followed by growth at a slower rate than in untreated samples. Assuming a hypothetical load of 10 cells/g or cm(2) of L. monocytogenes and S. aureus as an original contamination in an industrial situation, an E-beam treatment of vacuum-packed cooked ham slices at 2 kGy guarantees the microbiological safety of the product along its shelf life, even if a noticeable temperature (10 degrees C) abuse occur during its storage period. Likewise, the E-beam treatment gave rise to a substantial increase of the RTE cooked ham shelf life off-sensory features associated to the spoilage only were detected in non-treated samples (controls) after 8 and 18 days of storage at 10 degrees C and 7 degrees C, respectively.

Microbial transglutaminase for cold-set binding of unsalted/salted pork models and restructured dry ham.

The viability of using microbial transglutaminase (MTGase) as a cold-set binder for restructuring and manufacturing deboned dry ham (RDH) was evaluated. The influence of meat pre-treatment, preparation of the MTGase, packing system and set temperature on the binding rate and force was tested using pork models and deboned legs. The best binding parameters were obtained when meat surfaces were evenly distributed with salts (NaCl, KNO(3), NaNO(2)) and then washed with a saline solution (W), afterwards powder (P) or liquid (L) MTGase was applied, and simultaneous salting and vacuum packing (S) set at 7 degrees C were performed. The RDH manufactured following these procedures (WPS and WLS) was stable during drying and could resist the handling and production process. Binding force increased (p<0.05) during 8 weeks of drying. Scanning electron microscopy analysis showed an increase of cross-links during the drying period of RDH related to the increase in binding force.

Safety and quality of ready-to-eat dry fermented sausages subjected to E-beam radiation.

The inactivation kinetics in the death of Listeriainnocua NTC 11288 (more radioresistant than five different strains of Listeriamonocytogenes) and Salmonella Enterica serovar Enteritidis and S. enterica serovar Typhimurium by E-beam irradiation has been studied in two types of vacuum-packed RTE dry fermented sausages ("salchichon" and "chorizo") in order to optimize the sanitation treatment of these products. A treatment of 1.29kGy was calculated to reach the food safety objective (FSO) according to the "zero tolerance" criterion for the three strains. No irradiation treatment was necessary to meet the 10(2)c.f.u./g microbiological criterion for L. monocytogenes. Dry fermented sausages treated with ⩽2kGy had negligible sensory (appearance, odour and taste) modifications. Therefore, this treatment produces safe dry fermented sausages with similar sensory properties to the non-irradiated product.

Elimination of Listeria monocytogenes from vacuum-packed dry-cured ham by E-beam radiation.

The inactivation kinetics for Listeria monocytogenes Scott A (CIP 103575, serotype 4b) and Listeria innocua (NTC 11288) after E-beam radiation were studied in vacuum-packed ready-to-eat dry-cured ham to optimize the sanitation treatment of this product. A treatment of 1.12 kGy was calculated to reach the food safety objective according to the U.S. Department of Agriculture criterion. No irradiation treatment is necessary to meet the European Union microbiological criterion for this bacterium. No changes (at doses < or =4 kGy) in the 2-thiobarbituric acid reactive substances values and texture were observed. Dry-cured hams treated with 1 and 2 kGy had negligible sensory modifications (appearance, odor, and flavor). However, the application of 3 and 4 kGy resulted in an increase in the intensity of off-odors and off-flavors. Despite these effects, all irradiated vacuum-packed dry-cured hams treated at < or =4 kGy were deemed acceptable for trading.

Impact of feeding and rearing systems of Iberian pigs on volatile profile and sensory characteristics of dry-cured loin.

The effect of growing pigs on free-range (FR) or in confinement with three different diets [acorn (A), acorn and grass (A-G) and formulated diet (FD)] on composition, volatile profile and sensory characteristics of dry-cured loin was studied. The FR, A and A-G diets, in comparison with FD, induce a higher α- and γ-tocopherol concentration, which limits the TBARs values at 24h of air exposure. Sixty volatile compounds were identified in the headspace, including 14 aldehydes, 10 hydrocarbons, eight alcohols, five ketones, four furans, four pyrazines, four sulphur compounds, three acids, three esters, three phenols, one pyridine and one pyrrole. Volatiles from amino acid catabolism stressed the difference among batches FR being the batch with the highest level of these compounds. Products from FD showed the lowest fat content and L(∗) value. FR loins obtained the highest scores for appearance, odour and flavour in the rank order test sensory analysis.

Enrichment of dry-cured ham with α-linolenic acid and α-tocopherol by the use of linseed oil and α-tocopheryl acetate in pig diets.

The use of α-linolenic acid and α-tocopherol enriched pork on the fatty acids and the sensory characteristics of Spanish dry-cured hams have been studied. Five batches of hams were manufactured using the posterior legs of pigs fed on diets with the same ingredients except for the oil source: sunflower (C), linseed (L) or linseed and olive (1/1, w/w, LO). Two different α-tocopheryl acetate concentrations [20 (C, L and LO) or 220 (LOE and LE)mg/kg diet] were used. Biceps femoris and Semitendinosus/Semimembranosus muscles from hams with low polyunsaturated fatty acid n-6/n-3 ratio (less than 3) were obtained from animals fed on linseed and linseed/olive oil enriched diets. However, hams from animals fed on diets added with linseed and α-tocopheryl acetate (20mg/kg diet) (batch L) were rejected by consumers because of less acceptable sensory characteristics and higher TBARs. The remaining hams had satisfactory sensory and nutritional characteristics.

Tensile properties of cooked meat sausages and their correlation with texture profile analysis (TPA) parameters and physico-chemical characteristics.

The possibilities of using breaking strength (BS) and energy to fracture (EF) for monitoring textural properties of some cooked meat sausages (chopped, mortadella and galantines) were studied. Texture profile analysis (TPA), folding test and physico-chemical measurements were also performed. Principal component analysis enabled these meat products to be grouped into three textural profiles which showed significant (p<0.05) differences mainly for BS, hardness, adhesiveness and cohesiveness. Multivariate analysis indicated that BS, EF and TPA parameters were correlated (p<0.05) for every individual meat product (chopped, mortadella and galantines) and all products together. On the basis of these results, TPA parameters could be used for constructing regression models to predict BS. The resulting regression model for all cooked meat products was BS=-0.160+6.600∗cohesiveness-1.255∗adhesiveness+0.048∗hardness-506.31∗springiness (R(2)=0.745, p<0.00005). Simple linear regression analysis showed significant coefficients of determination between BS (R(2)=0.586, p<0.0001) versus folding test grade (FG) and EF versus FG (R(2)=0.564, p<0.0001).

Raman spectroscopy study of the structural effect of microbial transglutaminase on meat systems and its relationship with textural characteristics.

Raman spectroscopy and texture analysis (TPA) studies were carried out to determine the effect of adding different levels of microbial transglutaminase (MTGase) to meat systems. This addition produced a significant (p<0.05) increase in hardness, springiness and cohesiveness in the meat systems. Raman spectroscopy analysis revealed the occurrence of secondary structural changes in meat proteins due to MTGase. Modifications in the amide I (1650-1680cm(-1)) and amide III (1200-1300cm(-1)) regions indicated a significant (p<0.05) decrease in α-helix content, accompanied by a significant (p<0.05) increase in ß-sheets and turns due to the addition of the enzyme to meat systems. Significant (p<0.05) correlations were found between these secondary structural changes in meat proteins and the textural properties (hardness, adhesiveness, springiness and cohesiveness) of meat systems.

Magnetic resonance imaging, rheological properties, and physicochemical characteristics of meat systems with fibrinogen and thrombin.

Magnetic resonance imaging (MRI) and textural and physicochemical analyses were carried out to evaluate the effect of fibrinogen and thrombin (Fibrimex) addition to meat systems formulated with and without NaCl. For this purpose, different model systems were elaborated: fibrinogen and thrombin (FT), meat emulsion (ME), and meat emulsion with fibrinogen and thrombin (MEFT), with 0, 1, and 2% of NaCl. The addition of fibrinogen-thrombin to meat emulsions results in a gel network with modified physicochemical and textural characteristics, increasing the hardness and springiness. The addition of NaCl at 2% to FT and MEFT systems reduced the gel hardness. MRI parameters (T2, T1, and apparent diffusion coefficient) indicated that systems with fibrinogen and thrombin (FT and MEFT) presented a structure with many and large pores, bulk water, and higher translational motion of water. Significant correlations were found between MRI, texture, and physicochemical parameters.

Breaking strength of dry fermented sausages and their correlation with texture profile analysis (TPA) and physico-chemical characteristics.

In order to assess its usefulness for monitoring textural properties of dry fermented sausages (chorizo, salchichon, salami, fuet and mini-fuet) the determination of breaking strength (BS) was evaluated. Texture profile analysis (TPA) and physico-chemical measurements (pH, aw, dry matter, fat content) were also performed. The BS determined by tensile test and TPA analysis produced complementary information that allowed these meat products to be grouped according to four different textural profiles. These profiles were characterized (p<0.05) by the values of BS, hardness, adhesiveness, cohesiveness and springiness. Multivariate analysis confirmed that BS and TPA parameters were correlated significantly (p<0.00005). On basis of these results, TPA parameters could be used to construct regression models to predict BS and therefore, to obtain a more complete textural property description of the dry fermented sausages. The resulting regression model was BS=-0.777+0.728∗adhesiveness-16881∗cohesiveness+1884.61∗springiness+0.042∗hardness (R(2)=0.634, p<0.00005).

Effect of dietary linseed oil and α-tocopherol on pork tenderloin (Psoas major) muscle.

The effect of linseed oil and α-tocopheryl acetate on the fatty acid composition and the susceptibility to oxidation of lipid fraction from pork tenderloin (Psoas major) muscle has been studied. Muscles were obtained from animals fed on diets with the same ingredients excepting the oil source [sunflower (C), linseed (L) and linseed and olive (1/1, w/w) (LO)] and α-tocopherol [20 (C, L and LO) or 200 (LOE and LE) mg/kg diet]. The n-6/n-3 ratio in pork tenderloin was markedly modified by dietary linseed oil administration, which was due to the increase in the C18:3n-3 (and total n-3 fatty acids) and the decrease in the C18:2n-6 (and total n-6 fatty acids) contents (P<0.05). The α-tocopherol content of tenderloin from batches LE and LOE was about 2.8 mg/kg of muscle, significantly greater (P<0.05) than about 0.7 mg/kg muscle found in tenderloin from pigs receiving C, L and LO. Dietary supplementation with α-tocopheryl acetate markedly reduced tenderloin lipid oxidation from animals fed diets enriched in n-3 fatty acids (L or LO vs LE or LOE).

Antimutagenic effect of fruit and vegetable ethanolic extracts against N-nitrosamines evaluated by the Ames test.

The inhibitory effect of nine fruit and vegetable ethanolic extracts against the mutagenicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA), and N-nitrosopiperidine (NPIP) was evaluated by means of the Ames test. Licorice ethanolic extract was the only one that showed an inhibitory effect (ranging from moderate to strong) against mutagenicity of all N-nitrosamines tested. This ethanolic extract showed the greatest inhibition effect against NPIP (72%), NDMA (45%), and NPYR (39%). The greatest inhibition effect (51%) of the mutagenicity of NDBA was shown by kiwi ethanolic extract. Vegetable and fruit ethanolic extracts that exhibited an antimutagenic effect (at the range 50-2000 microg/plate), in decreasing order, against NDMA and NPYR were as follows: licorice > kiwi > carrot and licorice > broccoli > pineapple > kiwi, respectively. Decreasing orders against NDBA and NPIP were, respectively, kiwi > onion > licorice = garlic > green pepper > carrot and licorice > garlic > pineapple > carrot.