HS-SPME GC-MS characterization of volatiles in processed walnuts and their oxidative stability.

Processed walnuts including hot air-dried and roasted walnuts were prepared. Volatiles in raw and processed walnuts were analyzed using head-space solid phase microextraction combined with gas chromatography and mass spectrometry. Oxidative stability of hot air-dried walnuts in different antioxidants, with or without vacuum package was studied to find a proper package for oxidation stability of hot air-dried walnuts. The results showed that there were 14 volatiles in raw walnuts, 28 in hot air-dried walnuts and 38 in roasted walnuts. The changes of oil quality indices, total phenols, malondialdehyde and free radical scavenging activities during storage at 60 °C showed that the oil oxidation increased with storage time. The addition of antioxidants and vacuum package could slow down the oxidation. Vacuum aluminum foil package (14 × 20 cm) can delay the oil oxidation and extend the shelf life to ~ 230 days of hot air-dried walnuts at 20 °C. With added antioxidant this was extended to ~ 257 days.

Foal meat volatile compounds: effect of vacuum ageing on semimembranosus muscle.

BACKGROUND: Cooked meat flavor arises through a combination of thermally generated aroma volatile and nonvolatile compounds in a matrix of muscle fiber, connective tissue, and fat. Ageing could affect meat odor, taste, and flavor by the development of odor compounds in the raw product. The aim of the work is to assess the ageing effect on the volatile compounds profile by solid-phase microextraction and gas chromatography-mass spectrometry analysis of foal meat vacuum packaged for storage at 4 °C for a period of 14 days. RESULTS: Only pentane and 3,7-dimethylnonane were significantly affected by ageing time (P < 0.01). Octanal and nonanal presented an increasing trend with higher values at 14 ageing days compared with six ageing days (P < 0.01). CONCLUSIONS: Ageing poorly affects the volatile compounds production of foal meat. Probably, 14 days is considered to be a short maturation time in vacuum packaging for foal meat. © 2018 Society of Chemical Industry.

Effects of vacuum and modified atmosphere on textural parameters and structural proteins of cultured meagre (Argyrosomus regius) fillets.

The influence of two preservation strategies (vacuum package and modified atmosphere package) on the post-mortem changes of textural parameters, pH, water holding capacity, sarcoplasmic and myofibrillar proteins, and collagen content of meagre (Argyrosomus regius) fillets was studied. Fillets were stored in a cold room in aerobic (control, C), vacuum (V) and modified atmosphere (MA) package. Samples were withdrawn at six sampling points throughout 15-day storage, and post-mortem changes were assessed. The textural parameters were significantly enhanced in V and MA compared to C. Both V and MA treatments reduced the intensity of a group of myofibrillar protein fractions (140-195 kDa) and increased insoluble collagen compared to C. Consequently, the post-mortem flesh softening in C was attributed to increased proteolysis in both intracellular and extracellular structural proteins. The preservation of the textural and biochemical characteristics of meagre fillets subjected to V and MA treatments makes these two treatments highly recommendable for the commercialization of meagre fillets.

Shelf-life extension of vacuum-packaged meat from pheasant (Phasianus colchicus) by lactic acid treatment.

We investigated the influence of lactic acid treatment of pheasant meat before vacuum-packaged storage of 3, 7, and 10 d at +6°C on microbiota and pH. Breast muscle samples were collected from carcasses of slaughtered as well as from hunted (shot) wild pheasants. Immersion of meat samples in 3% (wt/wt) lactic acid for 60 s effectuated a significant drop in pH of approximately 0.5 to 0.7 units, which remained during the entire storage period. In parallel, total aerobic counts of such treated and stored samples were on an average 1.5 to 1.7 log units lower than in non-acid-treated samples. Similar results were found for Enterobacteriaceae. A significant decrease in pH was measured at d 7 and 10 in the acid-treated samples in comparison with the untreated ones. In summary, the immersion of pheasant breast meat cuts in dilute lactic acid significantly reduced microbiota during vacuum-packed storage, even at slight temperature abuse conditions.

Evaluating the Safety of Sous-Vide Cooking for Beef Products Inoculated with Single Strains of Salmonella enterica and Escherichia coli O157.

Sous-videcooking is a growing trend among retailers and consumers. Foodborne pathogens may survive the cooking if nonvalidated parameters are used or if pathogens have enhanced thermalresistance. Pathogen inactivation from sous-vide cooking was determined when introduced directly to beef products or via contaminated spices, and with or without a finishing step. Beef products (ground beef, tenderized, and nontenderized steaks) were inoculated with pathogens (Salmonella Montevideo and Escherichia coli O157:NM) in three ways: 1) directly onto the meat 2) ground black pepper incorporated into the recipe 3) ground pepper equilibrated at 30% RH (4 d) prior to incorporation. Beef samples were vacuum-packaged and submerged in a 62.5°C water bath for 120 min. Samples were sampled at 5, 10, 20, and 120 min (recommended from a partner quality study), and a duplicate was grilled to a specific internal temperature (74°C for ground beef, 57°C for steaks) and sampled. Sous-vide cooking reduced pathogen populations by >5 log CFU/g after most treatment times, but less than grilled counterparts (ca. 1-2 log CFU/g difference; p < 0.05).There were no statistically significant differences between inoculation methods, but the tenderization of steaks resulted in significantly lower reductions of pathogens from sous-vide cooking (p < 0.05). Thisresearch challenged sous-vide cooking parameters (120 min, 62.5°C). It showed sous-vide alone lowered pathogens by >4 log CFU/g after most 20-min treatments, but 120-min sous-vide treatments or grilling would be needed for >5-log reductions.Contaminated pepper led to less consistent reductions during the cooking process, yet 2-h sous-vide still achieved a 5-log reduction. Sous-vide cooking instructions must be validated as more products and recipes are marketed.

Evaluation of vacuum packaging for extending the shelf life of Sardinian fermented sausage.

Salsiccia sarda or Sardinian fermented sausage is a traditional dry-fermented sausage included in the list of traditional food products of Sardinia (Italy). At the request of some producing plants, the possibility of extending the shelf life of the vacuum-packed product up to 120 days was evaluated. Manufacturing of 90 samples, representing 3 different batches of Sardinian fermented sausage was carried out in two producing plants (A and B). In the packaged product and subsequently every 30 days for four months (T0, T30, T60, T120), the following analyses were conducted on all samples: physicochemical characteristics, total aerobic mesophilic count, Enterobacteriaceae count, detection of Listeria monocytogenes, Salmonella spp., mesophilic lactic acid bacteria, and coagulase-positive Staphylococci. Moreover, surfaces in contact and surfaces not in contact with food were sampled in both producing plants. Sensory profile analysis was also performed for every analysis time. At the end of the extended shelf life, pH values were equal to 5.90±0.11 (producing plant A) and 5.61±0.29 (producing plant B). Water activity mean values at T120 were 0.894±0.02 (producing plant A) and 0.875±0.01 (producing plant B). L. monocytogenes was detected in 73.3% (33/45) of the samples from producing plant A, with mean levels of 1.12±0.76 log10 CFU/g. In producing plant B, L. monocytogenes was never detected. Enterobacteriaceae were detected in 91.1% (41/45) of samples in producing plant A with mean values of 3.15±1.21 log10 CFU/g, and in 35.5% (16/45) samples in producing plant B samples with mean values of 0.72±0.86 log10 CFU/g. Salmonella and Staphylococcus aureus were never detected. Regarding environmental samples, the sites that were most contaminated by L. monocytogenes were the bagging table (contact surface) and processing room floor drains (non-contact surface) with a prevalence of 50% each (8/16 positive samples for both sampling sites). Sensory analysis results showed that at T30 the overall sensory quality was at its highest;moreover, the visual-tactile aspect, the olfactory characteristics, the gustatory aspects, and the texture showed significant differences in samples throughout the shelf life, with a decreased intensity at 120 days of storage. Overall, the quality and sensory acceptance of the vacuumpacked Sardinian fermented sausage was not affected until 120 days of shelf-life. However, the possible contamination by L. monocytogenes calls attention to the hygienic management of the entire technological process. The environmental sampling was confirmed as a useful verification tool during control.

Effects of chitosan coating combined with thermal treatment on physicochemical properties, bacterial diversity and volatile flavor of braised duck meat during refrigerated storage.

The current study aimed to assess the impact of chitosan coating (0.005 g/mL) combined with thermal treatment (85 °C for 30 min) on tenderness, lipid and protein oxidation, bacterial diversity, and volatile flavor compounds in braised duck leg meat under vacuum packaging during refrigerated storage (4 °C for 15 days). The findings revealed that the three preserved treatments significantly increased tenderness from days 1 to 3. There was a substantial decrease from days 6 to 12 compared to the control, but no significant differences were observed on day 15. Compared with the control, the three preserved treatments reduced TBARS values by 25.8%-78.6% (from days 6 to 12) and total sulfhydryl concentrations by 24.1%-75.7% (from days 3 to 9). The combination treatment had the lowest values (carbonyl concentration, TVC, and TEC) compared to the chitosan coating and thermal treatment, indicating a significant synergistic effect. The proportions of the four primary spoilage organisms, Brochothrix, Weissella, Acinetobacter, and Pseudomonas, were 74.8%, 76.3%, 70.7%, and 49.7% in control, chitosan coating, thermal treatment, and combination treatment, respectively. The combination treatment produced the most volatile flavor compounds (38 compounds) at the end of storage (15 days). Hexanal, 1-nonanal, 1-octen-3-ol, and 2, 3-octanedione were the main volatile flavor compounds, and the average relative peak area was above 80. Therefore, chitosan coating and thermal treatment could be developed as synergistic methods to preserve braised duck meat.

Survival of Escherichia coli o157:h7 co-cultured with different levels of pseudomonas fluorescens and lactobacillus plantarum on fresh beef.

The purpose of this study was to investigate the effect of different levels of Pseudomonas fluorescens (10(2) and 10(6) log10 cfu/ml) and Lactobacillus plantarum (10(2) and 10(4) log10 cfu/ml) on the growth of Escherichia coli O157:H7 on beef loins. Beef loins inoculated with E. coli O157:H7 and P. fluorescens were aerobically stored for 7 days at 4 ºC, while those inoculated with E. coli O157:H7 and L. plantarum were vacuum packaged and stored for 8 weeks at 4 ºC. Aerobic Plate Counts (APC), E. coli O157:H7 and either P. fluorescens or L. plantarum counts were determined at different storage intervals. For the aerobically packaged beef loins, E. coli O157:H7 was detected throughout the 7 day storage period regardless of the P. fluorescens level in the inoculum. For the vacuum packaged beef loins, similar inoculum levels of E. coli O157:H7 and L. plantarum allowed E. coli O157:H7 to survive until week 5 of storage, while a higher inoculum level of L. plantarum inhibited E. coli O157:H7 from week 3. Once fresh beef has been contaminated with E. coli O157:H7, the level of P. fluorescens in the background flora does not inhibit its survival and growth. However, under vacuum storage, the application of L. plantarum as a biopreservative inhibits the survival of E. coli O157:H7 on beef. The higher the level of L. plantarum in the system, the earlier the onset of the inhibition. Farmers and abattoirs have to strengthen preventive strategies to eliminate contamination of beef carcasses with E. coli O157:H7.

Wafer-Level Vacuum-Packaged Translatory MEMS Actuator with Large Stroke for NIR-FT Spectrometers.

We present a wafer-level vacuum-packaged (WLVP) translatory micro-electro-mechanical system (MEMS) actuator developed for a compact near-infrared-Fourier transform spectrometer (NIR-FTS) with 800-2500 nm spectral bandwidth and signal-nose-ratio (SNR) > 1000 in the smaller bandwidth range (1200-2500 nm) for 1 s measuring time. Although monolithic, highly miniaturized MEMS NIR-FTSs exist today, we follow a classical optical FT instrumentation using a resonant MEMS mirror of 5 mm diameter with precise out-of-plane translatory oscillation for optical path-length modulation. Compared to highly miniaturized MEMS NIR-FTS, the present concept features higher optical throughput and resolution, as well as mechanical robustness and insensitivity to vibration and mechanical shock, compared to conventional FTS mirror drives. The large-stroke MEMS design uses a fully symmetrical four-pantograph suspension, avoiding problems with tilting and parasitic modes. Due to significant gas damping, a permanent vacuum of ≤3.21 Pa is required. Therefore, an MEMS design with WLVP optimization for the NIR spectral range with minimized static and dynamic mirror deformation of ≤100 nm was developed. For hermetic sealing, glass-frit bonding at elevated process temperatures of 430-440 °C was used to ensure compatibility with a qualified MEMS processes. Finally, a WLVP MEMS with a vacuum pressure of ≤0.15 Pa and Q ≥ 38,600 was realized, resulting in a stroke of 700 µm at 267 Hz for driving at 4 V in parametric resonance. The long-term stability of the 0.2 Pa interior vacuum was successfully tested using a Ne fine-leakage test and resulted in an estimated lifetime of >10 years. This meets the requirements of a compact NIR-FTS.

Effect of a nano-silver coating on the quality of fresh turkey meat during storage after modified atmosphere or vacuum packaging.

Nano-silver is used in consumer products due to its antibacterial properties. The aim of this study was to evaluate the effect of a nano-silver-coated film on the quality of turkey meat during vacuum-sealed and modified atmosphere packaging up to 12 days of storage. In the first part of the experiment, turkey breasts were packaged using either vacuum packaging or modified atmosphere packages (MAPs) and contained films with or without a nano-silver coating (control film). Parameters such as pH, electrical conductivity, color (lightness L*, redness a*), myoglobin redox forms, thiobarbituric acid-reactive substances (TBARS), biogenic amines (BAs), total viable bacterial counts, Pseudomonas species counts, and Enterobacteriaceae species counts were evaluated on storage days 4, 8, and 12. In the second part of the study, the antimicrobial effect of a nano-silver-coated film on turkey breast was evaluated after inoculation with Escherichia coli (E. coli). Turkey meat packaged with the nano-silver film exhibited lower a* values on days 1 (3.15 ± 0.62), 4 (3.90 ± 0.68), and 8 (4.27 ± 0.76) compared to the packaged meat with the control film (3.41 ± 0.73, 4.35 ± 0.94, 4.85 ± 0.89, respectively), indicating special optical properties of nanoparticles. Concerning the BAs, silver packaged meat showed higher values of tyramine on day 12 (1274 ± 392 ng/g meat) and cadaverine on day 4 (1224 ± 435 ng/g meat) compared to the normal packaged products (647 ± 576 and 508 ± 314 ng/g meat, respectively). MAP meat revealed higher L* and TBARS values and lower microbial counts than the vacuum packaged products on all days. The MAP meat also showed lower a* results on days 4 and 8 and higher metmyoglobin (metMb) values on days 8 and 12 compared to th E: vacuum products. In the inoculation study, the microbial counts of the turkey meat were comparable between the two film types. The study showed that the nano-silver coating did not exhibit any advantageous effects on the quality and microbiological parameters of the turkey meat.

Survival of Escherichia coli o157: h7 co-cultured with different levels of Pseudomonas fluorescens and Lactobacillus plantarum on fresh beef

The purpose of this study was to investigate the effect of different levels of Pseudomonas fluorescens (10² and 10(6)log10 cfu/ml)and Lactobacillus plantarum (10² and 10(4)log10 cfu/ml)on the growth of Escherichia coli O157:H7 on beef loins. Beef loins inoculated with E. coli O157:H7 and P. fluorescens were aerobically stored for 7 days at 4 ºC, while those inoculated with E. coli O157:H7 and L. plantarum were vacuum packaged and stored for 8 weeks at 4 ºC. Aerobic Plate Counts (APC), E. coli O157:H7 and either P. fluorescens or L. plantarum counts were determined at different storage intervals. For the aerobically packaged beef loins, E. coli O157:H7 was detected throughout the 7 day storage period regardless of the P. fluorescens level in the inoculum. For the vacuum packaged beef loins, similar inoculum levels of E. coli O157:H7 and L. plantarum allowed E. coli O157:H7 to survive until week 5 of storage, while a higher inoculum level of L. plantarum inhibited E. coli O157:H7 from week 3. Once fresh beef has been contaminated with E. coli O157:H7, the level of P. fluorescens in the background flora does not inhibit its survival and growth. However, under vacuum storage, the application of L. plantarum as a biopreservative inhibits the survival of E. coli O157:H7 on beef. The higher the level of L. plantarum in the system, the earlier the onset of the inhibition. Farmers and abattoirs have to strengthen preventive strategies to eliminate contamination of beef carcasses with E. coli O157:H7.

Growth Potential of Individual Strains of Listeria monocytogenes in Fresh Vacuum-Packaged Refrigerated Ground Top Rounds of Beef.

Separate inocula of four strains of Listeria monocytogenes were prepared at 4°C and inoculated (3.58 to 4.67 log10 colony forming units [CFU]/g) in top round ground beef (< 4.0% fat) patties (78.8 ± 6.7 g) of normal (5.47 ± 0.03) or high (6.14 ± 0.08) pH, which were stored (4°C) vacuum-packaged for 56 days and analyzed for L. monocytogenes , total aerobic plate counts (APC) and pH. In normal-pH ground beef, strain N-7143 (serotype 3a), multiplied from 4.25 ± 0.71 log10 CFU/g at day of inoculation to 6.53 ± 0.34 log10 CFU/g at 35 days of storage (P < 0.05); a 2.3 log10 CFU/g increase. Populations of strain Na-19 (serotype 3b) increased 1.8 log10 CFU/g in 35 days of storage, while numbers of strain Na-16 (serotype 1/2a) did not change (P > 0.05) during the 56 days of storage. Strain Scott A (serotype 4b) decreased in numbers from 4.00 ± 1.21 log10 CFU/g at day-0 to 2.72 ± 0.98 log10 CFU/g at 56 days. Populations of strain Scott A were lower (P < 0.05) than other strains after 21 days of storage. In high-pH ground beef, populations of strains Na-19, N-7143 and Na-16 increased (P < 0.05) by 2.87, 2.64 and 2.24 log10 CFU/g, respectively, in 28 days. Populations of strain Scott A did not change significantly (P > 0.05), and they were lower (P< 0.05) than populations of other strains at 28 days. The results indicated that although growth of L. monocytogenes in vacuum-packaged, refrigerated ground beef was slow, it proceeded more rapidly in product of pH values above 6.0, and depended on strain of the pathogen tested.