Effect of modified atmosphere and temperature abuse on the growth from spores and cereulide production of Bacillus weihenstephanensis in a cooked chilled meat sausage

The effect of modified atmosphere packaging (MAP) on the germination and growth of toxin producing psychrotolerant Bacillus spp is not well described. A model agar system mimicking a cooked meat product was used in initial experiments. Incubation at refrigeration temperature of 8 °C for 5 weeks of 26 Bacillus weihenstephanensis including two emetic toxin (cereulide) producing strains showed that B. weihenstephanensis is sensitive to MAP containing CO₂. The sensitivity to 20% CO₂ was dependent on strain and oxygen level, being increased when oxygen was excluded from the MAP. Growth from spores was observed at the earliest within 2 weeks when 20% CO₂ was combined with 2% O₂ and in 3 weeks when combined with “0”% O₂ (the remaining atmosphere was made up from N₂). Results were validated in a cooked meat sausage model for two non-emetic and one emetic B. weihenstephanensis strain. The packaging film oxygen transfer rates (OTR) were 1.3 and 40 ml/m²/24 h and the atmospheres were 2% O₂/20% CO₂ and “0”% O₂/20% CO₂. Oxygen availability had a large impact on the growth from spores in the MAP meat sausage, only the most oxygen restricted condition (OTR of 1.3 ml/m²/24 h and “0”% O₂/20 % CO₂) inhibited growth of the three strains during 4 weeks storage at 8 °C. Cereulide production was undetectable during storage at 8 °C irrespective of choice of the MAP (quantified by liquid chromatography mass spectrometry/mass spectrometry). MAP storage at 8 °C for 1 and 3 weeks followed by opening of packages and temperature abuse for 1.5 h daily at 20 °C during 1 week resulted in increased cell counts and variable cereulide production in the meat sausage. A pre-history at 8 °C for 1 week in MAP with OTR of 1.3 or 40 ml/m²/24 h and 2% O₂ resulted in cereulide concentrations of 0.816 – 1.353 µg/g meat sausage, while a pre-history under the most oxygen restricted condition (OTR of 1.3 ml/m²/24 h, “0”% O₂/20 % CO₂) resulted in minimal cereulide production (0.004 µg/g meat sausage) at abuse condition. Extension of MAP storage at 8 °C for 3 weeks followed by abuse resulted in a substantially reduced cereulide production.Data demonstrates that MAP can be used to inhibit growth of a psychrotolerant toxin producing Bacillus spp. during chill storage at 8 °C, and substantially reduce the risk of emetic food poisoning at abuse condition. Results are of relevance for improving safety of ready to eat processed chilled foods of extended durability.     

Combined effect of MAP and active compounds on fresh blue fish burger

The combined effects of three essential oils [thymol, lemon extract and grapefruit seed extract (GFSE)] and modified atmosphere packaging conditions (MAP) on quality retention of blue fish burgers was studied and discussed. In particular, samples were packaged in air and in three different gas mix compositions: 30:40:30 O₂:CO₂:N₂, 50:50 O₂:CO₂ and 5:95 O₂:CO₂. During a 28-day storage period at 4 °C, the nutritional, microbiological and sensorial quality of the packed products was assessed. The potential development of biogenic amines was also evaluated.The obtained results highlight the possibility to improve the microbial quality of blue fish burgers by using very small amount of thymol (110 ppm), GFSE (100 ppm) and lemon extract (120 ppm) in combination with MAP. Based primarily on microbiological results, the combined use of the tested natural preservatives and a packaging system characterized by a high CO₂-concentration, was able to guarantee the microbial acceptability of fish burgers until the 28th day of storage at 4 °C. On the other hand, results from sensory analyses showed that sensorial quality was the sub-index that limited the burgers shelf life (to about 22–23 days), even if the proposed strategy was also effective in minimizing the sensory quality loss of the product having no effect on its nutritional quality.     

Addition of synthetic and natural antioxidants to α-tocopheryl acetate supplemented beef patties: effects of antioxidants and packaging on lipid oxidation

Friesian steers (n=5), aged 26–27 months, were fed a diet containing 2000 (supplemented) IU α-tocopheryl acetate/head/day for approximately 50 days prior to slaughter. Muscularis semimembranosus muscles from supplemented cattle were held in frozen storage (−20°C×12 weeks) following which they were minced and divided into five batches. The batches contained: (1) control, containing only vitamin E supplemented beef (C); (2) vitamin E supplemented beef with 4% soya oil (S); (3) vitamin E supplemented beef mixed with 0.2% Duralox NMC dissolved in 4% soya oil (R1); (4) vitamin E supplemented beef mixed with 0.25% Herbalox type 25 (containing 25 natural antioxidant extracts of rosemary) dissolved in 4% soya oil (R2); and (5) vitamin E supplemented beef mixed with a 1:1 mixture of 0.01% (w/w) BHA and 0.01% (w/w) BHT dissolved in 4% soya oil (B). The meat was then aerobically packaged (A) or packaged under the following modified atmospheres (MAP); 30:70 (M₁); 70:30 (M₂) or 80:20 (M₃) (O₂:CO₂). Oxidative stability (TBARS) and Hunter ‘a’ values (redness) were determined in all beef patties over 8 days of refrigerated (4°C) storage. Under MAP or aerobic packaging conditions, elevated oxygen levels brought about increased (P<0.05) TBARS numbers during refrigerated storage. However, the addition of rosemary extracts or BHA/BHT significantly (P<0.05) improved the oxidative stability of dietary α-tocopheryl acetate supplemented beef. Rosemary extracts were as effective in reducing TBARS as the combination of synthetic antioxidants, BHA/BHT.     

The triacylglycerol preparation of conjugated linoleic acid reduces lipid oxidation in irradiated, cooked ground beef patties

It is proposed that conjugated linoleic acid (CLA) would depress the lipid oxidation caused by irradiation of cooked, aerobically stored ground beef patties. The free fatty acid (FFA–CLA) and triacylglycerol (TAG–CLA) preparations of CLA were added at 0%, 1%, 2%, or 4% during the grinding process. Patties were irradiated at 1.5–2.0 kGy and frozen at −20 °C. Subsequently, the patties were tempered to 4 °C, cooked to 70 °C and held at 4 °C for 7 d. Enrichment of ground beef with CLA increased the cis-9,trans-11 and CLA trans-10,cis-12 CLA isomers in ground beef patties, even after cooking. Weight loss (P = 0.03) and percentage fat (P = 0.05) were higher in irradiated beef patties than in control patties. Irradiation decreased the concentration of α-linolenic acid (18:3n − 3) in the ground beef by over 60% (P = 0.07), whereas thiobarbituric acid reactive substances (TBARS) values were higher (P = 0.004) in irradiated beef patties than in control patties. The 1% concentration of added TAG–CLA reduced TBARS in irradiated ground beef patties, whereas 2% and 4% FFA–CLA depressed TBARS (CLA type × percentage interaction P = 0.04). Irradiation increased the cardboard and painty aromatic attributes (P  0.05), and FFA–CLA preparation increased the painty aromatic attribute and afterburn aftertaste, but these effects were not observed with the TAG–CLA preparation (CLA type × treatment interaction P < 0.04). Adding 1% TAG–CLA to ground beef during grinding can reduce lipid oxidation in irradiated, cooked ground beef patties without the negative aftertastes associated with the FFA–CLA preparation.     

Effect of dietary α-tocopherol supplementation on color and lipid stability in pork

Myoglobin and lipid oxidation are major causes of quality deterioration in fresh pork. A process to enhance color and lipid stability would prove valuable to the pork industry given the current trend of centralized packaging and distribution to retail markets. Our objective was to determine the effects of dietary α-tocopherol (α-Toc) supplementation on color and lipid stability in ground pork, and loin chops stored in modified atmosphere packaging (MAP). Yorkshire crossbred pigs (n=20) were randomized into two groups and fed diets containing 48 (CON) or 170 mg α-Toc acetate/kg feed (VIT-E) for 6 weeks before slaughter. Plasma α-Toc concentration was measured weekly. Post-slaughter, Boston butt shoulders were ground, formed into patties with or without 1.5% salt, and stored fresh at 4°C for 0, 2, 4, or 6 days, and frozen at −20°C for 45 or 90 days. Pork loin chops were packaged aerobically and stored at 4°C for 0, 2, 4 or 6 days, or in MAP at 4°C for 7, 10 or 13 days prior to Hunter L*,a*,b* and TBARS analyses. α-Toc concentration of longissimus dorsi, psoas major, biceps femoris, semimembranosus and semitendinosus muscles was determined. Plasma α-Toc was greater (P<0.05) in VIT-E animals compared with CON and α-Toc concentrations were greater (P<0.05) in all VIT-E muscles compared with CON. TBARS values of both fresh and salted patties were less in VIT-E than in CON meat following 6 days at 4°C; VIT-E TBARS of salted patties were less (P<0.05) after 45 days at −20°C compared with CON. α-Toc supplementation did not influence (P>0.05) color of aerobically packaged or MAP chops, or of fresh or salted pork patties. α-Toc supplementation reduced TBARS formation in fresh and salted pork but had no significant impact on color.     

Microbiological characteristics of poultry patties in relation to packaging atmospheres

Microbial characteristics under different atmospheres (vacuum, air, MAP₁: 80% O₂/20% CO₂ and MAP₂: 5% O₂/65% N₂/30% CO₂) of poultry patties made of a mixture of ostrich, chicken and turkey meat were evaluated. The meat preparations were examined for changes in pH, colour properties (CIE L*, a*, b*), headspace composition, and bacterial counts (total viable cell, psychrotrophs, Enterobacteriaceae, lactic acid bacteria, Staphylococcus spp., Brochothrix thermosphacta, Pseudomonas spp.). The use of a high O₂ atmosphere (MAP₁) quickly leads to a loss of the appealing red colour. A limited alteration occurred with use of MAP₂ and vacuum. For total viable counts a cell load higher than 8 log cfu g^?1 for the samples packaged in air, MAP₁ and MAP₂ at the end of storage was observed. Whereas, for the vacuum packed samples the cell load never reached values higher than 8 log cfu g^?1. Enterobacteriaceae, B. thermosphacta and Pseudomonas spp. cell load was less with the vacuum (7.60, 5.06 and 7.17 log cfu g^?1, respectively) and MAP₂ packaging (7.08, 5.60 and 7.40 log cfu g^?1, respectively). However, the high microbial loads suggest that an improvement of the microbiological quality of poultry meat is necessary if the producers are going to propose this new meat preparation on the market.     

Sensory shelf life determination of a processed meat product ‘rullepølse’ and microbial metabolites as potential indicators

Sensory profiling was performed for a Danish lightly fermented heat-processed cold cut pork product termed ‘rullepølse’. Product samples were stored under modified atmosphere (MAP, 30% CO₂/70% N₂) for 0, 28 and 34 days and with subsequent aerobic storage for 4 days (MAP–OPEN) at temperatures of 4 °C and 8 °C. Microbial growth and metabolism was also measured with a focus on lactic acid bacteria (LAB) and their organic acid metabolites including lactic acid, acetic acid and α-ketoisocaproic acid. These acids were examined for sensory shelf life indexing potential for the ‘rullepølse’. Storage temperature exerted distinct impacts on the sensory characterised shelf life of ‘rullepølse’ stored under MAP and MAP–OPEN conditions. The MAP stored ‘rullepølse’ with subsequent 4 days storage in air (MAP–OPEN) could be stored for at least 28 days at 4 °C without a decrease in the sensory quality when opened. Whilst MAP stored ‘rullepølse’ at 8 °C with subsequent open storage (MAP–OPEN), compared to the lower temperature displayed a reduced shelf life of less than 28 days if sensory quality of the ‘rullepølse’ was to be maintained. The stage of sensory deterioration was correlated with high bacterial counts exceeding 10⁶ CFU g⁻¹. With respect to indexing ability of the examined organic acids none were found to have clear potential for prediction of the sensory deterioration.     

Behaviour of Listeria monocytogenes in the presence of Listeria innocua during storage of minced beef under vacuum or in air at 0°C and 10°C

Minced beef was inoculated with low levels (1·2–1·7 log₁₀cfu g⁻¹) of Listeria monocytogenes or Listeria innocua, or a combination of the two strains. Inoculated samples were stored at 0 or 10°C under two packaging atmospheres (aerobic and vacuum) for up to 28 days and surviving organisms recovered on Palcam Agar. The only significant increases in numbers of Listeria spp. occurred in samples held at 10°C under aerobic conditions. In vacuum packs, growth of both strains was inhibited. Under aerobic conditions meat pH increased from an initial value of pH 5·85 to c. 8·85 within 28 days. The pH of vacuum packaged meat declined to c. 4·95 during the same period. These differences in pH may be related to differences in the nature and effects of different background microflora that were observed to develop under each of these packaging conditions.Pseudomonas spp. predominated in aerobically stored beef, whereas in vacuum packed beef lactic acid bacteria predominated. No significant differences were observed between the growth rates of Listeria spp. inoculated into beef mince in pure and mixed culture. This suggests that the more frequent prevalence of Listeria innocua than Listeria monocytogenes in meat and meat products is not due to overgrowth or inhibition of the pathogen (Listeria monocytogenes) by the non-pathogen(Listeria innocua) during low-temperature storage.     

Effect of lactate-enhancement, modified atmosphere packaging, and muscle source on the internal cooked colour of beef steaks

Earlier studies on lactate-mediated colour stability in beef did not address the possible influence on cooked colour. Our objective was to examine the effect of lactate-enhancement, muscle source, and modified atmosphere packaging (MAP) on the internal cooked colour of beef steaks. Longissimus lumborum (LL) and Psoas major (PM) muscles from 16 (n = 16) beef carcasses (USDA Select) were randomly assigned to 4 enhancement treatments (non-injected control, distilled water-enhanced control, 1.25% and 2.5% lactate), and fabricated into 2.54-cm steaks. Steaks were individually packaged in either vacuum (VP), high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), or carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), and stored for 0, 5, or 9 days at 1 °C. At the end of storage, surface and internal colour (visual and instrumental) was measured on raw steaks. Steaks were cooked to an internal temperature of 71 °C, and internal cooked colour (visual and instrumental) was evaluated. Lactate-enhancement at 2.5% level resulted in darker (P < 0.05) cooked interiors than other treatments. Interior cooked redness decreased (P < 0.05) during storage for steaks in VP and HIOX, whereas it was stable for steaks in CO. Our findings indicated that the beef industry could utilise a combination of lactate-enhancement and CO MAP to minimise premature browning in whole-muscle beef steaks.     

Combined effect of an oxygen absorber and oregano essential oil on shelf life extension of rainbow trout fillets stored at 4 °C

In the present study the combined effect of an O₂ absorber and oregano essential oil (0.4% v/w) on shelf life extension of rainbow trout fillets (Onchorynchus mykiss) stored under refrigeration (4 °C) was investigated. The study was based on microbiological [TVC, Pseudomonas spp., Lactic Acid Bacteria, H₂S-producing bacteria including Shewanella putrefaciens, Enterobacteriaceae and Clostridium spp.), physicochemical (pH, PV, TBA, TVBN and Drip loss) and sensory (odor, taste) changes occurring in the product as a function of treatment and storage time. Aerobically-packaged rainbow trout fillets stored at 4 °C were taken as control samples. Results showed that TVC exceeded 7 log cfu/g on day 4 of storage for control samples, day 7–8 for samples containing oregano oil, day 9 for samples containing the O₂ absorber and day 12–13 for samples containing the O₂ absorber and oregano oil. Pseudomonas spp., Enterobacteriaceae and LAB were only partially inhibited by the O₂ absorber and/or the oregano oil. In all cases the inhibition effect was more pronounced when the combination of O₂ absorber with oregano essential oil was used. pH decreased from an initial value of 6.65–6.09 and subsequently increased to 6.86 due to formation of protein decomposition products. % Drip loss ranged between 7% and 11–12% at the end of the product shelf life. PV values ranged between 11.4 and 27.0 meq O₂/kg oil while malondialdehyde (MDA) ranged between 9.6 and 24.5 mg/kg. TVBN ranged between 10.6 and 54.6 mg/kg at the time of sensory rejection. Sensory shelf life was 4 days for the control samples, 7–8 days for samples containing oregano oil, 13–14 days for samples containing the O₂ absorber and 17 days for samples containing the O₂ absorber plus oregano oil.     

Shelf life of ready to use peeled shrimps as affected by thymol essential oil and modified atmosphere packaging

In this work the influence of different packaging strategies on the shelf life of ready to use peeled shrimps was investigated. First, the effectiveness of the coating (Coat) and the active coating loaded with different concentrations of thymol (Coat-500, Coat-1000, and Coat-1500) on the quality loss of the investigated food product packaged in air was addressed; afterwards, the thymol concentration that had shown the best performance was used in combination with MAP (5% O₂; 95% CO₂). Microbial cell load of main spoilage microorganisms, pH and sensorial quality were monitored during the refrigerated storage. Results of the first step suggested that the sole coating did not affect the microbial growth. A slight antimicrobial effect was obtained when the coating was loaded with thymol and a concentration dependence was also observed. Moreover, the active coating was effective in minimizing the sensory quality loss of the investigated product, it was particularly true at the lowest thymol concentration. In the second step, the thymol concentration (1000 ppm) that showed the strike balance between microbial and sensorial quality was chosen in combination with MAP. As expected, MAP significantly affected the growth of the mesophilic bacteria. In particular, a cell load reduction of about 2 log cycle for the samples under MAP respect to that in air was obtained. Moreover, the MAP packaging inhibited the growth of the Pseudomonas spp. and hydrogen sulphide-producing bacteria. The MAP alone was not able to improve the shelf life of the uncoated samples. In fact, no significant difference between the control samples packaged in air and MAP was observed. Whilst, the use of coating under MAP condition prolonged the shelf life of about 6 days with respect to the same samples packaged in air. Moreover, when the MAP was used in combination with thymol, a further shelf life prolongation with respect to the samples packaged in air was observed. In particular, a shelf life of about 14 days for the active coating under MAP compared to the same samples in air (5 days) was obtained.     

Evaluation and predictive modeling of shelf life of minced beef stored in high-oxygen modified atmosphere packaging at different temperatures

The aims were: (1) to follow the freshness decay of minced beef stored in high-oxygen modified atmosphere packaging at different temperatures (4.3, 8.1 and 15.5 °C) by applying traditional methods (microbiological counts, color evaluation, thiobarbituric acid assay TBA, headspace gas composition) and e-nose; (2) to model the decay kinetics to obtain information about the maximum shelf life as function of storage conditions. The minced beef, packaged in modified atmosphere was supplied by a manufacturer at the beginning of its commercial life. The study demonstrated the ability of the traditional methods to describe the kinetics of freshness decay. The modeling of the experimental data and the comparison with microbiological or chemical thresholds allowed the setting, for each index, of a stability time above which the meat was no longer acceptable. The quality decay of meat was also evaluated by the headspace fingerprint of the same set of samples by means of a commercial e-nose. A clear discrimination between “fresh” and “old” samples was obtained using PCA and CA, determining at each temperature a specific range of stability time. The mean value of the stability times calculated for each index was 9 days at 4.3 °C (recommended storage temperature), 3–4 days at 8.1 °C (usual temperature in household refrigerators) and 2 days at 15.5 °C (abuse temperature). Resolution of the stability times allowed calculation of mean Q₁₀ values, i.e. the increase in rate for a 10 °C increase in temperature.The results show that the Q₁₀ values from the traditional methods (3.6–4.0 range) overlapped with those estimated with e-nose and color indexes (3.4 and 3.9, respectively).     

Synergic antimicrobial activity of lysozyme, nisin, and EDTA against Listeria monocytogenes in ostrich meat patties

Synergic antimicrobial activity of lysozyme (250 ppm), nisin (250 ppm), and disodium ethylenediamine tetraacetic acid (EDTA) (20 mM) against Listeria monocytogenes and meat-borne spoilage bacteria in ostrich patties packaged in air and vacuum was studied. The antimicrobial treatment decreased the L. monocytogenes population in ostrich patties below the official limit of the European Union (<2 log CFU/g). The total viable counts for the treated samples (air and vacuum) showed a reduction of 1 log cycle until to 2 d of storage; after this period the cell load increased. Moreover, the reduction of 2 log cycle for the lactic acid bacteria was observed. Enterobacteriaceae and Pseudomonas spp. were not affected by the antimicrobial treatment in both packaging atmospheres. Sensory evaluation did not differ between treated and untreated samples as regard to the color. The ostrich patties packaged in vacuum had a desirable odor during the storage time and were not affected by antimicrobial treatment. The off-odors for the patties packaged in air developed faster in the control while the odor scores for the treated samples remained above the rejection point up to the end of storage. PRACTICAL APPLICATION: Great interest is developing in food bio-preservation, because of the ever-increasing needs to protect consumers' health and to valorize the naturalness and safety of food products.     

Inactivation of Escherichia coli O157:H7 on surface-uninjured and -injured green pepper (Capsicum annuum L.) by chlorine dioxide gas as demonstrated by confocal laser scanning microscopy

Cells of Escherichia coli O157:H7 on uninjured and injured surfaces of green pepper were inactivated by 0·15–1·2 mg l⁻¹ClO₂gas treatments. A membrane-surface-plating method was used for resuscitation and enumeration of E. coli O157:H7 treated with ClO₂. The location and viability ofE. coli O157:H7 on uninjured and injured green pepper surfaces after ClO₂gas treatments were visualized using confocal laser scanning microscopy (CLSM). Live and dead cells of E. coli O157:H7 on pepper surfaces were labeled with a fluorescein isothiocyanate-labeled antibody and propidium iodide, respectively. A 7·27 log reduction of E. coli O157:H7 on uninjured green pepper surfaces was obtained with a 0·60 mg l⁻¹ClO₂gas treatment for 30 min at 20°C under 90–95% relative humidity. For injured surfaces, a 6·45 log reduction was achieved with a 1·2 mg l⁻¹ClO₂gas treatment. Each ClO₂gas treatment (0·15–1·2 mg l⁻¹ClO₂) for inoculated bacteria on uninjured surfaces showed significantly more reductions (1·23–4·24 log) than for those on injured surfaces (P<0·05). The microphotographs of CLSM showed that bacteria preferentially attached to injured surfaces and those bacteria could be protected from bacterial reduction by the injuries. This study indicates that ClO₂gas treatment can be a potential effective method of pathogen reduction for fresh fruits and vegetables.     

Survival kinetics of Ephestia kuehniella eggs during 46–75 °C heat treatment

The effect of heat treatment on the survival of Ephestia kuehniella eggs was examined. Samples of 60 eggs were immersed in hot water at constant temperature in the 46–75 °C range for 5–1200 s. Following heat treatment and cooling, the eggs were stored at 24 ± 1 °C in a growth chamber for 7 days before survival evaluation. Statistical analysis of the data demonstrated that the thermal survival kinetics were best represented by a first-order reaction. The rate constant had an Arrhenius-type dependence over the 54–75 °C temperature range. Kinetic parameters were estimated by non-linear regression. The activation energy (E_a) and rate constant (k_ref) at the reference temperature (T_ref = 64.8 °C), were determined as 102.2 ± 6.2 kJ mol⁻¹ and 0.061 ± 0.003 s⁻¹, respectively, over the 54–75 °C temperature range. A 0.01% survival rate was obtained after 50 s at 75 °C. The data at temperatures below 50 °C were not in accordance with those at higher temperatures. Above this temperature, mortality was likely due to physiological disorders, as noted on a DSC thermogram.     

Use of Lysozyme,Nisin, and EDTA Combined Treatments for Maintaining Quality of Packed Ostrich Patties

ABSTRACT: The antimicrobial effectiveness of lysozyme, nisin, and ethylene diamine tetraacetic acid (EDTA) combination treatments (Mix₁: 250 ppm lysozyme, 250 ppm nisin, 5 mM EDTA; Mix₂: 500 ppm lysozyme, 500 ppm nisin, 5 mM EDTA) on bacterial growth of ostrich patties packaged in air, vacuum, and 2 different modified atmospheres (MAP₁: 80% O₂, 20% CO₂; MAP₂: 5% O₂, 30% CO₂, 65% N₂) was evaluated. Moreover, the lipid oxidation was evaluated as well as color and sensory characteristics. The growth of total viable counts and lactic acid bacteria were strongly inhibited by the antimicrobial treatments in all the running time (Inhibition Index >97%) whereas for Enterobacteriaceae and Pseudomonas spp. lower inhibition indices from 12% to about 28% were observed. The lipid oxidation was more pronounced in the control respect to the treated meat patties. Moreover, the mixture at low concentration of lysozyme and nisin showed the best antioxidative effect. High concentrations of lysozyme and nisin showed the greatest color loss. Also, off-odors for the untreated patties developed faster than the treated samples. Practical Application: Great interest is developing in food bio-preservation, because of the ever-increasing needs to protect consumers' health and to valorize the naturalness and safety of food products.     

Chitosan effects on quality properties of Greek style fresh pork sausages

The effect of chitosan (0.5% and 1%) added individually or in combination with nitrites (150 ppm) on microbiological (Total Viable Counts, Lactic acid bacteria, Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae, yeasts and moulds), physicochemical-chemical (pH, chemical composition, lipid oxidation) and sensory properties of fresh pork sausages stored at 4 °C for 28 days was investigated. Chitosan addition resulted in significant (p < 0.05) inhibition of microbial growth, while nitrites did not seem to protect sausages from microbial spoilage. A gradual reduction of nitrites was observed till the end of storage, when nitrites were almost depleted in all nitrite containing samples. The rate of lipid oxidation in fresh pork sausages was significantly decreased (p < 0.05) by addition of increasing levels of chitosan, while samples containing both chitosan and nitrites showed the lowest malondialdehyde (MDA) values, indicating a synergistic antioxidative effect. Consequently, the samples containing the combination of nitrites and chitosan at any level deteriorated less rapidly and were judged as more acceptable than all the other samples.     

Storage stability of jackfruit (Artocarpus heterophyllus) powder packaged in aluminium laminated polyethylene and metallized co-extruded biaxially oriented polypropylene during storage

Total colour difference (ΔE), rates of adsorbed moisture and sensory attributes of drum-dried jackfruit powder packaged in aluminium laminated polyethylene (ALP) and metallized co-extruded biaxially oriented polypropylene (BOPP/MCPP) pouches stored at accelerated storage (38 °C, with 50%, 75% and 90% relative humidity (RH)) were determined over 12 weeks period. The changes in total colour followed zero order reaction kinetics. Packaging materials, storage temperature and RH values significantly (p < 0.05) influenced the rates of adsorbed moisture of jackfruit powder. There was a significant (p < 0.05) decrease in the intensities of the fruity odour, taste and increase in the lumpiness of the jackfruit powder stored at 38 °C with 90% RH. The shelf life of jackfruit powder stored at 38 °C and 90% RH was limited by overall acceptability and the intensity of fruity odour, taste and lumpiness at week 8 of storage. Jackfruit powder stored at 28 °C remained stable and acceptable throughout the storage period for all RH values. The powder packaged in ALP significantly (p < 0.05) reduced total colour change, rates of adsorbed moisture, lumpiness intensity of jackfruit powder and was rated higher in terms of overall acceptability over BOPP/MCPP. Results of this study suggested that ALP packaging with storage conditions of 28 °C and RH less than 75% was better suited for keeping jackfruit powder.     

Crystalline stability of self-assembled fibrillar networks of 12-hydroxystearic acid in edible oils

The stability of organogels differs based on the organogelator concentration, storage temperature, and solvent type. Organogel post-crystallization annealing was monitored at 5 °C, 15 °C, 20 °C or 30 °C for up to 1 month. Gels, stored at 5 °C, had highly immobilized oil, as judged from large T₂ relaxation peaks at 50–70 ms determined by pulsed nuclear magnetic resonance (pNMR) and visual observations. When the gels were stored at 30 °C, the 50–70 ms T₂ relaxation peak shifted to longer relaxation times, indicating that the oil was more mobile than at 5 °C. Along with the increase in syneresis at 30 °C, the 12HSA network’s crystallinity was also greater, having fewer inclusions of liquid oil, as determined by pNMR. The highly branched network observed at 5 °C changed more in time with regards to crystallinity although it entrained the oil to a much greater extent than the gels stored at 30 °C.     

Synergistic effect of Pulsed Electric Fields and CocoanOX 12% on the inactivation kinetics of Bacillus cereus in a mixed beverage of liquid whole egg and skim milk

With a view to extending the shelf-life and enhancing the safety of liquid whole egg/skim milk (LWE–SM) mixed beverages, a study was conducted with Bacillus cereus vegetative cells inoculated in skim milk (SM) and LWE–SM beverages, with or without antimicrobial cocoa powder. The beverages were treated with Pulsed Electric Field (PEF) technology and then stored at 5 °C for 15 days. The kinetic results were modeled with the Bigelow model, Weibull distribution function, modified Gompertz equation, and Log-logistic models.Maximum inactivation registered a reduction of around 3 log cycles at 40 kV/cm, 360 µs, 20 °C in both the SM and LWE–SM beverages. By contrast, in the beverages supplemented with the aforementioned antimicrobial compound, higher inactivation levels were obtained under the same treatment conditions, reaching a 3.30 log₁₀ cycle reduction.The model affording the best fit for all four beverages was the four-parameter Log-logistic model.After 15 days of storage, the antimicrobial compound lowered Bacillus cereus survival rates in the samples supplemented with CocoanOX 12% by a 4 log cycle reduction, as compared to the untreated samples without CocoanOX 12%. This could indicate that the PEF-antimicrobial combination has a synergistic effect on the bacterial cells under study, increasing their sensitivity to subsequent refrigerated storage.