Radio frequency heating improves water retention of pork myofibrillar protein gel: An analysis from water distribution and structure.

This study was to explore effects of hot air assisted or not assisted radio frequency (RF, 27.12 MHz, 1.4 kW) heating with different electrode gaps (100 mm, 120 mm, and 140 mm) on the water-holding capacity (WHC) of myofibrillar protein (MP) gel and to understand the underlying mechanism through chemical forces, water distribution, and structure. The results showed that the MP gels heated by RF (100 mm) had the highest WHC and uniform gel network structure. As for RF with 100 mm electrode gap, the increased ionic and hydrogen bonds might be conducive to the WHC compared to water bath heating, which was verified by Low-field nuclear magnetic resonance results that the free water converted into the immobilized water. Raman spectroscopy results revealed that RF (100 mm) induced the self-assembly of ß-sheet to α-helix, which conduced to the stable and ordered gel network structure.

Effect of edible composite film based on chitosan and cumin essential oil-loaded nanoemulsion combined with low-dose gamma irradiation on microbiological safety and quality of beef loins during refrigerated storage.

This research was conducted to assess the combined effect of chitosan (Ch) film containing cumin essential oil nanoemulsion (CNE) and low-dose gamma irradiation (GI) at 2.5 kGy on microbiological safety and quality of beef loins during 21 days of chilled storage. The growth of mesophilic and psychrophilic bacteria, Enterobacteriaceae, and lactic acid bacteria were retarded in all treated groups (Ch, GI, Ch + CNE, Ch + GI, and Ch + CNE + GI groups) compared to control group during storage time. The treatments also slowed down the increasing level of total volatile basic nitrogen and pH during storage, while irradiation increased the levels of thiobarbituric acid reactive substances and protein carbonyls in beef loins. All treatments except Ch were effective to control the growth of inoculated pathogenic bacteria, including Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella typhimurium, in loin samples. The combination of Ch + CNE + GI was the most effective treatment to control the population of microbial flora and inoculated pathogens, slow down some physicochemical changes, and enhance the storage life of beef loins. As a result, the combination of active chitosan film and low-dose gamma irradiation can ensure microbiological safety and is suggested for long time preservation of beef during chilled storage.

Effect of freezing/irradiation/thawing processes and subsequent aging on tenderness, color, and oxidative properties of beef.

This study evaluated the use of gamma irradiation (3, 6 and 9 kGy) in frozen vacuum-packed beef and subsequent thawing and aging for up to 14 days. The effects on tenderness, color, and oxidative properties were determined and compared to non-irradiated controls for frozen/thawed and chilled vacuum-packed beef. The combined irradiation and freezing/thawing processes increased total exudate loss and reduced the meat water-holding capacity, regardless of the dose used. Myofibrillar fragmentation was favored by the freezing/thawing processes and negatively affected by irradiation. Lower shear force values were observed in the non-irradiated frozen/thawed samples. Frozen samples irradiated at 9 kGy had a higher percentage of soluble collagen, lipid peroxidation, and a more reddish color tone. The meat reducing capacity and oxygen consumption were reduced by freezing and further by irradiation, which also included accumulation of metmyoglobin. It was concluded that irradiation of frozen meat and its subsequent thawing and aging does not confer any additional advantages for beef technological quality.

Combined effects of gamma irradiation and aging on tenderness and quality of beef from Nellore cattle.

Combined effects of gamma irradiation (0, 3, 6 and 9 kGy) and aging (1 and 14 days) on quality attributes of vacuum-packaged beef from Nellore cattle were evaluated. The meat water holding capacity was affected by irradiation, increasing (p < 0.05) purge and cooking loss regardless of the dose used. Irradiation negatively affected myofibrillar fragmentation, but samples irradiated at 9 kGy had (p < 0.05) higher soluble collagen and lower shear force values. The meat metmyoglobin reducing activity was reduced (p < 0.05) by the irradiation process, inducing the metmyoglobin accumulation with increasing dose applied. Samples irradiated at 9 kGy presented (p < 0.05) higher lipid oxidation and lower oxymyoglobin proportion and color redness and chroma values. It was concluded that irradiation at 9 kGy combined with aging can be used as an effective tool for improving the tenderness of Nellore beef, but resulted in a discoloration of the beef.

Light exposure accelerates oxidative protein polymerization in beef stored in high oxygen atmosphere.

Protein oxidation of beef patties stored in high oxygen modified atmosphere packaging for 9 days was investigated. Meat was either stored in the dark, under light, or in the dark with addition of FeCl2/H2O2/myoglobin (forced oxidation). SDS-PAGE analysis showed high degree of protein polymerization for meat exposed to light, compared to the other samples. Light exposure induced reducible (disulfide) and non-reducible cross-links, while mainly disulfides were formed in meat stored in the dark. Light exposure was responsible for 58% loss of free thiols (Cys residues). No significant loss of other amino acid residues was observed and none of the most common oxidation products of tryptophan, tyrosine, and phenylalanine were detected. Intrinsic fluorescence measurements of tryptophan showed 27% loss in samples exposed to light, which was ascribed to loss of protein solubility via protein polymerization rather than tryptophan oxidation. Protein carbonyls were mainly detected in forced oxidized samples at Day 0.

Physicochemical and sensory properties of beef muscles after Pulsed Electric Field processing.

This study investigated the effects of pulsed electric field (PEF) processing on the sensory and physicochemical properties of beef biceps femoris (BF) and semitendinosus (ST) muscles. The fresh and frozen-thawed muscles were treated at an electric field strength of 0.8-1.1 kV/cm, pulse width of 20 µs, frequency of 50 Hz and specific energy of 130 kJ/kg. PEF treated samples improved meat tenderness and colour. However increased fat oxidation and increased saturated fatty acids were evident in PEF processed frozen samples. Temporal dominance of sensations results showed that although oxidation was the most dominant in temporal perception, the samples were only found to be detrimental to the sensory quality of PEF processed beef muscles stored for 7 days.

Efeito da radiação gama sobre a oxidação lipídica da carne bovina / Effect of gamma radiation on lipid oxidation of beef

Objetivou-se avaliar o efeito de diferentes doses de radiação (1, 2, 3, 6 e 9 kGy) sobre a oxidação lipídica de contrafilés bovinos pela determinação das substâncias reativas ao ácido 2-tiobarbitúrico (TBARS) e por cromatografia gasosa utilizando a técnica de microextração em fase sólida (SPME). As amostras irradiadas apresentaram maior concentração de aldeídos, com maior incidência de nonanal, independentemente da dose aplicada. Maiores concentrações de hexanal foram observadas nas amostras irradiadas por maiores doses (6 e 9 kGy), mas os maiores valores de TBARS foram observados nas amostras irradiadas por 3 e 6 kGy. Uma redução nos valores de aldeídos, especialmente nonanal e octanal, foi observada para amostras irradiadas por 2 kGy quando comparadas às demais amostras irradiadas. Conclui-se que o processo de irradiação aumentou o grau de oxidação das amostras, que consequentemente, aumentou a concentração dos aldeídos presentes.

Percepção sensorial do off-odor em carnes bovinas irradiadas em embalagens á vácuo contendo carvão ativado / Off-odor perception in irradiated beef vacuum packaged with charcoal

Objetivou-se avaliar a utilização de carvão ativo na redução de compostos voláteis responsáveis pelo off-odor de carnes bovinas irradiadas. Para tal, contrafilés bovinos, embalados a vácuo, com e sem carvão ativo, e irradiados (1, 2 e 3 kGy), foram analisados quanto a formação de compostos de enxofre e quanto a percepção sensorial de off-odor. O único composto de enxofre identificado nas amostras foi o dimetil sulfeto (DMS), sendo encontrado em menor concentração nas amostras irradiadas com carvão ativo na embalagem. Independentemente da utilização do carvão, os painelistas perceberam o off-odor das carnes irradiadas em qualquer dose quando comparado à carne não-irradiada. Quando foi comparado as carnes irradiadas com carvão em relação àquelas irradiadas sem carvão, os painelistas foram capazes de identificar o off-odor apenas nas amostras irradiadas com 1 kGy. Conclui-se que o carvão ativo reduziu a concentração de DMS na embalagem de carnes irradiadas.

Inactivation of Escherichia coli O157 and Salmonella Enteritidis in raw beef liver by gamma irradiation.

Irradiation of ground beef and beef liver inoculated with Escherichia coli O157 466 and DT66 and Salmonella Enteritidis 3313 were performed with gamma rays from cobalt-60 at refrigerated and frozen temperatures under air- and vacuum-packaged conditions. Results showed that D10 values for all pathogens in frozen beef liver were higher than those in frozen ground beef samples, with significant differences observed between the D10 values of E. coli O157 466 and S. Enteritidis 3313 under air-packaged conditions, as well as in E. coli O157 DT66 and S. Enteritidis 3313 under vacuum-packaged conditions. To verify effective bacterial inactivation under high bacterial-contamination levels (105-107 CFU/g), survival/death interfaces of E. coli O157 DT66 and S. Enteritidis 3313 inoculated in beef liver under vacuum-packaged and frozen conditions were constructed, with results suggesting that doses from 5.3 kGy to 5.5 kGy and 8.2 kGy-8.5 kGy would be sufficient to kill 105 CFU/g of E. coli O157 and S. Enteritidis 3313, respectively, at a 95%-99% predicted confidence interval. These results suggested that food matrixes containing high amounts of antioxidants (such as beef liver) and treated under frozen and vacuum-packaged conditions require additional consideration and evaluation for applications of irradiation treatment.

Rapid Communication: Effect of machine, anatomical location, and replication on instrumental color of boneless pork loins.

The objective was to determine the effect of machine, anatomical location, and replication (multiple readings) on instrumental color and to characterize the amount of variation each factor contributed to overall color. Instrumental color was measured three times on the anterior and three times on the posterior end of 250 pork loins with two different Minolta CR-400 Chroma meter devices. Each Minolta was programed to use a D65 illuminant, 2° observer with an 8 mm aperture, and calibrated with white tiles specific to each machine. Therefore, a total of 12 instrumental color measurements were collected on each loin. The VARCOMP procedure in SAS was used to estimate the proportion of variation contributed by each factor to CIE L*, a*, b*, chroma, and hue. Based on previous research, the average untrained consumer is able to distinguish between 3-L* units, 0.4-a* units, and 0.9-hue angle units. Loins evaluated with machine 1 were 0.71 L* units darker (P < 0.01), 1.09 b* units more yellow (P < 0.01), 0.47 chroma units more saturated (P < 0.01), and had a hue angle 5.12 units greater (P < 0.01) than when evaluated with machine 2 but did not differ (P = 0.24) in redness. The anterior portion of the loin was lighter, less red, more yellow, more saturated and had a greater hue angle than the posterior end (P < 0.01). All color trait values decreased (P < 0.01) as replication number increased. Inherent color differences among loins contributed the greatest proportion of variability for lightness (58%), redness (57%), yellowness (70%), saturation (70%), and hue angle (49%). Machine contributed 1% variability to lightness 3% to saturation, 23% to yellowness, and 31% to hue angle (31%) but did not contribute to variability for redness. Anatomical location contributed 41% to lightness, 43% to redness, 7% to yellowness, 27% to saturation, and 31% to hue angle. Replication did not contribute to total variation for any color traits, even though it did differ among measurements. Overall, there were differences in instrumental color values between the two machines tested, but those differences were likely less than the threshold for detection by a consumer. Even so, inherent color differences between loins were a greater contributor to total variability than the differences between the two machines. Therefore, it is more important to define the location of measurements than replication or machine when using a Minolta CR-400 when performing color evaluations, assuming the settings are the same.

Application of high temperature (14°C) aging of beef M. semimembranosus with low-dose electron beam and X-ray irradiation.

The effects of irradiation source (electron beam [EB] and X-ray [XR]), aging temperature (4°C and 14°C), and aging time (0, 3, 7, and 14days) were evaluated on microbial quality, physicochemical properties, and calpain-1 autolysis in beef M. semimembranosus. Regardless of irradiation source, irradiation prior to aging reduced the total number of aerobic bacteria in beef and this reduction was maintained during aging. Irradiation did not affect the pH, b⁎ value, shear force, or myofibrillar fragmentation index of beef at day 0. Degradation of sarcoplasmic and myofibrillar proteins was greater in beef aged at 14°C compared with beef aged at 4°C. EB- or XR-irradiated samples showed slower autolysis of calpain-1; however, beef tenderness was not affected. Therefore, EB or XR irradiation can be applied to beef prior to aging to control microbial growth during high temperature (14°C) aging, thus shortening the aging time without adversely affecting the physicochemical properties of beef.

Influence of Gamma Irradiation on Porcine Serum Albumin Structural Properties and Allergenicity.

Pork provides an ideal source of food energy; however, pork can elicit an allergic reaction, and porcine serum albumin (PSA) has been identified as a major allergen. This study examined the impact of gamma irradiation on the allergenicity and structural qualities of PSA; the PSA solution was gamma-irradiated at 1, 2, 4, 6, and 8 kGy. Allergenicity was investigated by immunoblotting and competitive indirect ELISA using serum from patients who are allergic to pork, and conformational changes in irradiated PSA were measured by circular dichroism, sulfhydryl group detection, and fluorescence emission spectra. The secondary and tertiary structures of gamma-irradiated PSA were altered, and the allergenicity of PSA was lowered by boosting the amount of irradiation. In addition, there is high correlation between depletion in the α-helix and immunoglobulin E-binding capability of PSA. The results show a new possibility in using gamma irradiation to reduce the allergenicity of pork products.

Simultaneous analysis of Cr and Pb in contaminated pork by laser-induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) as a rapid and green method was used to detect heavy metals Cr and Pb in pork contaminated in the lab. The laser-induced plasma was generated by a Q-switched Nd:YAG laser, and the LIBS signal was collected by a spectrometer with a charge-coupled device detector. The traditional calibration curves (CC) and multivariate partial least squares (PLS) algorithm were applied and compared to validate the accuracy in predicting the content of heavy metals in samples. The results demonstrated that the correlation coefficient of CC is poor by the classical univariate calibration method, so the univariate calibration analysis cannot effectively serve the quantitative purpose in analyzing heavy metals' residue in pork with a complex matrix. The analysis accuracy was improved effectively by the PLS method, and the correlation coefficient is 0.9894 for Cr and 0.9908 for Pb. The concentration of Cr and Pb in samples from a prediction set was obtained using the PLS calibration method, and the average relative errors for the 21 samples in the prediction set are lower than 6.53% and 7.82% for Cr and Pb, respectively. The investigated results display that the matrix effect would be reduced effectively during the quantitative analysis of pork by a LIBS-combined PLS model, and the predictive accuracy would be improved greatly compared to traditional univariate analysis.

Determination of 2-alkylcyclobutanones in ultraviolet light-irradiated fatty acids, triglycerides, corn oil, and pork samples: Identifying a new source of 2-alkylcyclobutanones.

Previous studies have established that 2-alkylcyclobutanones (2-ACBs) are unique radiolytic products in lipid-containing foods that could only be formed through exposure to ionizing radiation, but not by any other means of physical/heat treatment methods. Therefore, 2-ACBs are currently the marker molecules required by the European Committee for Standardization to be used to identify foods irradiated with ionizing irradiation. Using a spectrum of state-of-the-art analytical instruments, we present in this study for the first time that the generation of 2-ACBs was also possible when fatty acids and triglycerides are exposed to a non-ionizing, short-wavelength ultraviolet (UV-C) light source. An irradiation dosage-dependent formation of 2-ACBs was also observed in UV-C irradiated fatty acids, triglycerides, corn oil, and pork samples. With UV-C irradiation becoming an increasingly common food treatment procedure, it is anticipated that the results from this study will alert food scientists and regulatory officials to a potential new source for 2-ACBs.

RAPID COMMUNICATION: Impact of contemporary light sources on oxidation of fresh ground beef.

Meat color is considered one of the driving factors in consumer purchasing decisions. The objective of this study was to determine the impact of 2 different lighting sources on color and lipid oxidation of ground beef patties in a controlled environment. USDA Select top rounds ( = 20) were processed to produce ground beef at 2 different fat levels (5 and 25%) and made into patties (113.4 g). Patties were packaged with oxygen permeable polyvinyl chloride, assigned to one of three lighting treatments (low UV fluorescent [FLO], light emitting diode [LED], and no light [DRK, negative control]), and placed within deli cases at 5°C. Patty removal for evaluation occurred on retail display d 1, 3, 5, and 7. Objective color measurements were obtained using a HunterLab MiniScan 45/0 LAV. These values were utilized to determine myoglobin redox forms as a measure of myoglobin oxidation. Additionally, thiobarbituric acid reactive substances (TBARS) were measured to indicate lipid oxidation. Objective color measurement for a* (redness), decreased for all light treatments by retail display day ( < 0.0001). Oxymyoglobin values for all light treatments decreased daily but showed no differences between treatments until d 5 ( < 0.0001) where DRK > LED > FLO. Conversely, metmyoglobin values increased daily ( < 0.0001), but showed no differences between treatments until d 5 where FLO > LED > DRK. TBARS values increased by day for each fat percentage ( < 0.0001) with 5% fat patties having higher TBARS values indicating great oxidation occurring in the phospholipids than adipose tissues. Results indicate that light treatment affected discoloration and metmyoglobin formation in ground beef patties LED lighting may lead to increased meat quality shelf life in a retail setting.

Investigation of the effect of UV-LED exposure conditions on the production of vitamin D in pig skin.

The dietary intake of vitamin D is currently below the recommended intake of 10-20µg vitamin D/day. Foods with increased content of vitamin D or new products with enhanced vitamin D are warranted. Light-emitting diodes (LEDs) are a potential new resource in food production lines. In the present study the exposure conditions with ultraviolet (UV) LEDs were systematically investigated in the wavelength range 280-340nm for achieving optimal vitamin D bio-fortification in pig skin. A wavelength of 296nm was found to be optimal for vitamin D3 production. The maximum dose of 20kJ/m(2) produced 3.5-4µg vitamin D3/cm(2) pig skin. Vitamin D3 produced was independent on the combination of time and intensity of the LED source. The increased UV exposure by UV-LEDs may be readily implemented in existing food production facilities, without major modifications to the process or processing equipment, for bio-fortifying food products containing pork skin.

Determination of free cholesterol oxide products in food samples by gas chromatography and accelerated solvent extraction: influence of electron-beam irradiation on cholesterol oxide formation.

BACKGROUND: The aim of this study was to develop an efficient method for cholesterol oxide product (COP) determination in irradiated and non-irradiated ready-to-eat foods with high water content by gas chromatography-flame ionisation detector after accelerated solvent extraction (ASE), and derivatisation with a silylating reagent. RESULTS: The ASE solvent was an 85:15 v/v petroleum ether/chloroform mixture at 40 °C and 1500 psi followed by solid phase extraction. The ASE method was compared with the established lixiviation method, proving an advantageous alternative which reduces analysis time by a factor of 15 and solvent volume by 50%, and minimises the use of chlorinated solvents. COP derivative structures were identified by gas chromatography coupled with mass spectrometry. Analytical characteristics were determined from standards and recoveries were 63-95%, establishing the validity of the method. CONCLUSION: The results obtained and their analysis by chemometric techniques established COP formation in food samples after e-beam irradiation. Increase in COP concentration depended on both irradiation doses and food composition, mainly water and fat content, although linear correlations among variables were not found. © 2016 Society of Chemical Industry.