Effect of packaging and storage conditions on quality of shelled walnuts

The present study investigated the effect of packaging and storage conditions on quality of raw shelled walnuts. Walnut kernels were packaged in: (a) low density polyethylene (LDPE), 55 μm in thickness in air, (b) polyethylene terephthalate||polyethylene (PET||PE), 70 μm in thickness under N₂, and (c) PET-SiO_x||PE pouches, 62 μm in thickness under N₂. Samples were stored either under fluorescent light or in the dark at 4 or 20 °C for a period of 12 months. Quality parameters monitored were peroxide value (PV), hexanal, 2-thiobarbituric acid (TBA), odor, and taste of product. PV ranged between 0.3 for fresh walnut kernels and 31.4 meq O₂/kg oil for walnuts packaged in PE pouches exposed to light after 12 months of storage. Respective values for hexanal were <28.5 μg/kg and 36.0 mg/kg and for TBA ca. 0.2 and 11 mg MDA/kg. Values for odor ranged between 0.2 for fresh walnut kernels and 5.7 for walnut kernels packaged in PE exposed to light after 12 months of storage at 20 °C. Respective values for taste were 0.7 and 6.8. Taste proved to be a more sensitive attribute than odor. Based on shelf life (taste) values and PV data it is proposed that the upper limit value for PV is close to 10.0 meq O₂/kg walnut oil. Respective limit values for hexanal are 1–2 mg hexanal/kg walnut and for TBA is 1–2 mg malondialdehyde/kg walnut. Walnuts retained acceptable quality for ca. 2 months in PE-air, 4–5 months in PET||PE-N₂ and at least 12 months in PET-SiO_x||PE-N₂ pouches at 20 °C, with samples stored in the dark retaining slightly higher quality than those exposed to light. The effect of parameters investigated followed the sequence: temperature > degree of O₂ barrier > lighting conditions.     

Effect of washing with citric acid and packaging in modified atmosphere on the sensory and microbiological quality of sliced mushrooms (Agaricus bisporus L.)

The effect of washing with citric acid before slicing and the effect of modified atmosphere packaging on the sensorial and microbiological quality of sliced mushrooms when stored at 5 °C for up to 17 days was evaluated.The atmosphere generated with the perforated PVC film was similar to that of air atmosphere. The non-perforated PVC film generated CO₂ concentrations inside the packages ranging from 6.9% to 3.1% and O₂ concentrations ranging from 2% to 6% depending on the storage time. Washing with citric acid reduced microbial counts by 2.5 log units on day 0. The anti-microbial effect of citric acid decreased during storage but remained significant on each sampling day. Modified atmospheres reduced the microbial counts by 0.8 log units throughout storage. The effect of washing with citric acid combined with packaging in modified atmosphere resulted additive. The reduction of microbial counts avoided bacterial blotch in washed mushrooms during 17 days of storage at 5 °C.     

Preventive effect of tannic acid in combination with modified atmospheric packaging on the quality losses of the refrigerated ground beef

Chemical, microbiological and sensorial changes of ground beef treated without and with tannic acid (200 mg/kg) and stored in air and under modified atmosphere packaging (MAP) (80%O₂/20%CO₂ or 10%O₂/20%CO₂/70%N₂) were monitored during 15 days of storage at 4 °C. During the storage, samples treated with tannic acid and kept under all packaging conditions contained lower peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) with coincidental lower non-haem iron content, compared with non-treated counterparts (P < 0.05). The sample packed in high oxygen MAP treated without and with tannic acid had the higher oxymyoglobin and a^* values and received the higher likeness scores for colour, whereas the samples stored in air and under low oxygen MAP showed the lower values, regardless of tannic acid treatment. After 15 days of storage, myosin heavy chain (MHC) and actin of all tannic acid treated samples underwent less degradation than those without tannic acid treatment for all packaging conditions. Degradation of MHC was more pronounced in samples kept under MAP with high oxygen. Psychrophilic bacterial count (PBC) of all tannic acid treated samples was lower, compared with that of non-treated samples (P < 0.05), irrespective of packaging condition. Therefore, tannic acid treated samples stored under high oxygen MAP could maintain the red colour and retard lipid oxidation and microbial growth of ground beef during refrigerated storage.     

Non-destructive assessment of oxygen levels in industrial modified atmosphere packaged cheddar cheese

An optical oxygen analyser was used in a small-scale industrial trial to non-destructively assess modified atmosphere packaged (MAP) cheese and the packaging process. Sixty seven samples of cheddar cheese, packaged under standard MAP conditions of 70% N₂: 30% CO₂ were monitored for residual oxygen using disposable sensor “stickers” incorporated in each pack and a benchtop optical analyser. Three faulty packs with oxygen leaks were identified in days 1, 4 and 11 after packaging, while in the remaining packs low levels of residual oxygen (<0.75%) were observed, as expected. Residual oxygen was monitored over 4 months of product shelf life at +4 °C, along with measurement of microbial growth. Good correlation between this system and established (destructive) methods of quality assessment of food packs was found. The optical oxygen sensor system was shown to provide valuable information about performance of the packaging process, product storage conditions and food quality in a convenient, non-destructive and cost-efficient fashion.     

The growth,physiology and toxigenic potential of Bacillus cereus in cooked rice during storage temperature abuse

The effect of storage temperature abuse on the growth and physiology of Bacillus cereus in cooked rice was examined using plate counting and flow cytometry (FCM). Concurrently, toxigenic potential was measured through recording phosphatidylcholine-specific phospholipase C (PC-PLC) activity. Rice spiked with endospores was incubated at 4 °C, 10 °C or 18 °C for 6 days. Growth was not recorded at 4 °C, whereas >1.0 × 10⁶ CFU g^?1 were detected at 10 °C and 18 °C. PC-PLC activity was temperature dependent and was not destroyed by microwaving. FCM population profiling complemented plate count data, providing novel physiological data e.g. on the membrane integrity, redox or intracellular activities of cells over time during low temperature incubation.     

Antimicrobial activity of clove (Syzgium aromaticum) oil in inhibiting Listeria monocytogenes on chicken frankfurters

The ability of Listeria monocytogenes to survive and grow at refrigeration temperature in some ready to eat (RTE) poultry products is a public health concern. The inhibitory effect of clove oil (1% and 2%, v/w) applied to the surface of RTE chicken frankfurters was determined on seven strains of L. monocytogenes inoculated at low (10²–10³ cfu/g) or high cell numbers (10⁴–10⁶ cfu/g), and stored at 5 °C for 2 weeks or at 15 °C for 1 week. All strains of L. monocytogenes survived and grew on control frankfurters at 5 °C and 15 °C but growth was inhibited under both storage conditions in the presence of either 1% or 2% clove oil. Depending on the sensory considerations, the addition of clove oil to frankfurters may be an effective strategy to control L. monocytogenes in chicken frankfurters.     

Efficiency of high pressure treatment on inactivation of pathogenic microorganisms and enzymes in apple,orange, apricot and sour cherry juices

The purpose of this study was to investigate the effect of high hydrostatic pressure with a mild heat treatment on Staphylococcus aureus 485, Escherichia coli O157:H7 933 and Salmonella Enteritidis FDA in apple, orange, apricot and sour cherry juices. The effectiveness of the treatment on polyphenol oxidase activity in apple juice and pectinesterase activity in orange juice were also determined. An inoculum of microorganisms was completely inactivated at 350 MPa and 40 °C in 5 min. The residual polyphenol oxidase activity in apple juice after treatment at 450 MPa and 50 °C for 60 min was obtained as 9 ± 2.2%. The residual pectinesterase activity in orange juice after treatment at 450 MPa and 50 °C for 30 min was determined as approximately 7 ± 1.6%. It compares with 12 ± 0.2% at a treatment of 40 °C and 450 MPa for 60 min. Pressure resistant isoenzymes were thought to be responsible for the final residual activity. The inactivation is irreversible and the enzyme is not reactivated upon storage. High pressure processing constitutes an effective technology to inactivate the enzymes in fruit juices. Pressures higher than 400 MPa can be combined with mild heat (<50 °C) to accelerate enzyme inactivation.     

Microbial and quality evaluation of green peppers stored in biodegradable film packaging

The effects of polylactic acid (PLA) based biodegradable film packaging on the microbial and physicochemical quality of green peppers (Capsicum annuum L.) were compared to the effects of low-density polyethylene (LDPE) film packaging, and perforated LDPE film packaging. Each package containing green peppers was heat-sealed and stored for 7 days at 10 °C. The microbial levels (aerobic bacteria, coliform bacteria, and yeast and moulds) and physicochemical properties such as colour, weight loss, hardness, ascorbic acid concentration, O₂ and CO₂ concentrations, were monitored during storage. Results indicated that the physicochemical properties of colour, hardness, ascorbic acid concentration, and microbial levels (total aerobic bacteria, and moulds and yeasts) did not show remarkable changes during storage period. The microbial levels in coliform bacteria were increased by less than 1 log CFU/g (0.2 log CFU/g) in the biodegradable film packaging, 2.3 log CFU/g in LDPE film package, and less than 1 log CFU/g (0.9 log CFU/g) in the perforated LDPE film package, after 7 days storage period. The results suggest that the biodegradable film with higher water vapor permeability can be used to maintain the quality and sanitary conditions (protection from microbial and insect contamination) of freshly harvested green peppers in modified atmosphere packaging.     

Patulin accumulation in apples during postharvest: Effect of controlled atmosphere storage and fungicide treatments

The aim of this study was to assess the opportunities of Penicillium expansum to develop and produce patulin in apples under two different CA storage methods (LOW and U-LOW) at 1 °C. Differences in lesion diameter and patulin accumulation depending on CO₂ and O₂ partial pressure were studied. Further apple rot and patulin production during a three days post-storing stage at 20 °C was also monitored so that effect of further storage at room temperature could be assesed.Two lots of apples of Golden variety with different ripeness degrees were used. Half of each lot was fungicide treated. Apples were inoculated with patulin producer P. expansum strains and stored at 1 °C for either two month or 2.5 months at both LOW and U-LOW conditions. The extent of lesions and patulin accumulation both at the end of CA cold storage and after three days at 20 °C were assessed. CA storage conditions had strong significance in P. expansum growth on apples and factors such as fruit ripeness, fungicide treatment and time at the storage room had significant influence. In general, bigger lesions were observed under U-LOW than under LOW conditions, lesions being similar or bigger when increasing the storage time from 2 to 2.5 months. P. expansum grew faster in riper apples, although fungicide application was clearly more effective for ripe rather than for underripe apples. Although lesions were evident after both storage conditions, no patulin was detected. Increase of lesion when fruits were subsequently stored at 20 °C was evident in all cases and patulin was detected at this moment. No differences in patulin content were found at this stage between LOW and U-LOW stored apples.     

Effect of orange dietary fibre,oregano essential oil and packaging conditions on shelf-life of bologna sausages

The objective of this work was to study the effect of orange dietary fibre (1%) (ODF), oregano essential oil (0.02%) (OEO) and the storage conditions (vacuum, air and modified atmosphere) on the shelf-life of bologna sausage. Samples with ODF + OEO stored in vacuum packaging showed the lowest TBA values. ODF + OEO samples stored in vacuum packaging showed the lowest aerobic and lactic acid bacteria counts. The sensory evaluation scores were similar for samples with ODF + OEO and stored either in air or vacuum packaging. Orange dietary fibre and oregano essential oil could find a use in the food industry to improve the shelf-life of meat products.     

The occurrence of volatile and semi-volatile aromatic hydrocarbons in virgin olive oils from north-eastern Italy

Twenty eight mono- (MAHs) and polyaromatic hydrocarbons (PAHs) were simultaneously determined in fifty-four virgin olive oils from three successive crops in the same geographical region. MAHs such as: toluene, C2-, C3- and C4-benzenes, and PAHs species containing 2, 3 and 4 aromatic rings were detected and quantified. MAHs were predominant in all of the samples, and had a mean concentration of 677 μg/kg. The mean concentration of total light PAHs was 80 μg/kg. Mean concentrations of C3- and C4-benzenes, which had not been previously quantified in olive oils, were 268 and 35 μg/kg, respectively. Finally, differences among crop years were evaluated, and the hypothetical daily intake of each aromatic hydrocarbon through virgin olive oil consumption was derived. The mean intake of single aromatic hydrocarbons ranged from 0.1 to 3.1 μg/day, while the mean exposures calculated for total MAHs and light PAHs were 15.6 and 1.8 μg/day, respectively.     

Effect of combined ozone and organic acid treatment for control of Escherichia coli O157:H7 and Listeria monocytogenes on enoki mushroom

This study evaluated the effects of ozonated water (1, 3, and 5 ppm) alone with different exposure times (0.5, 1, 3, or 5 min), and combinations of 3 ppm ozone with 1% organic acids (acetic, citric, or lactic acids) during 5-min exposure for control of Escherichia coli O157:H7 and Listeria monocytogenes on enoki mushroom and to observe the regrowth of these pathogenic bacteria on treated enoki mushroom during storage for 10 days at 15 °C. Results showed that ozone treatment gave less than 1.0- and 0.5-log count reductions on E. coli O157:H7 and L. monocytogenes, respectively. Efficacy was improved with combined 3 ppm ozone and 1% citric acid treatment, resulting in 2.26- and 1.32-log count reductions, respectively. During storage at 15 °C (10 days) after combined treatment and packaging, populations of E. coli O157:H7 and L. monocytogenes increased to more than 8.0 log cfu/g, indicating that the combined treatment did not have a residual antimicrobial effect during storage. Although the storage study did not show control of these pathogens, the combined ozone–organic acid treatment was more effective than individual treatments in reducing initial population levels of these pathogens on enoki mushroom.     

Preliminary hydrocarbon analysis of crude oils from Umutu/Bomu fields,south west Niger Delta Nigeria

Seven different crude oil samples were collected from two oil fields in the Niger Delta Nigeria. The bulk properties of these crude oils which include API gravity, reid vapour pressure; kinematic viscosity, dynamic viscosity, moisture, gum content and cloud point were analysed. Aliphatic biomarkers were used as supporting tool to deduce the geochemical characteristics such as thermal maturity, depositional environments, source of organic matter and extent of biodegradation. Results show that API° gravity ranged from 29.00° to 85.00°, specific gravity 0.65 to 0.88, 3.00 to 9.00, reid vapour pressure 3.00 to 9.00 kPa, kinematic viscosity 0.90 to 10.10 cSt, dynamic viscosity 0.70 to 8.90 cP, moisture content 0.13% to 26.00%, gum content 6.27 to 45.84 mg/L, cloud point 3.00 to 12.00 °C, pour point ?7.00 to 4.00 °C and flash point <30.00 °C. Distribution of n-alkanes (Pr/Ph, and isoprenoide/n-alkanes ratios) reflects that the oil samples originated mainly from terrestrial organic sources deposited in an oxic paleoenvironment.     

Effects of pulsed electric field treatments on quality of peanut oil

The effects of pulsed electric fields (PEF) treatment on physicochemical properties of peanut oil were investigated in this paper. Compositions of fatty acid, acid value (AV), peroxide value (PV), as well as carbonyl group value (CGV) of various PEF-treated peanut oil samples with different storage time were determined by GC/MS and AOCS standard methods. GC/MS analysis showed that little change of the oil composition was observed after PEF treatment. However, after being treated by various PEF treatments and stored at 40 °C for 100 days, the biggest increment of AV was 0.69 mg g⁻¹, which was lower than that of untreated peanut oil (0.79 mg g⁻¹). The PV significantly increased from 4.8 meq kg⁻¹ untreated oil to 11.5 meq kg⁻¹ PEF treated oil (50 kV cm⁻¹). And the increase extent of CGV of oil samples during the 100 d’ storage period was decreased with increasing electric field strength. During the storage period, the differences of AV, PV, and CGV of PEF-treated sample during storage period were less than that of untreated oil, which implied that the PEF treatment could restrain the speed of lipid oxidation reaction thus extending the shelf-life of oil rich products.     

Temperature distribution in Spanish domestic refrigerators and its effect on Listeria monocytogenes growth in sliced ready-to-eat ham

In order to evaluate the increase of L. monocytogenes concentration during home storage, a low level of the pathogen (<10 CFU/g) was inoculated in sliced ham. Two storage temperatures (5 °C and 9 °C) were selected from a previous study in 33 home refrigerators. Three days of storage or less were necessary to reach the regulated limited concentration (100 CFU/g), at both temperatures. When storage time was extended to 5 days, the pathogen achieved risky values (>10³ CFU/g).     

Inactivation of Staphylococcus spp. strains in whole milk and orange juice using ultra high pressure homogenisation at inlet temperatures of 6 and 20 °C

The objective of this work was to evaluate the inactivation induced by ultra high pressure homogenisation (UHPH) of Staphylococcus aureus ATCC 13565 and Staphylococcus carnosus CECT 4491 inoculated into milk and orange juice considering the effect of inlet temperature of the sample (6 and 20 °C) on the lethality values and on the production of sublethal injuries. Samples of UHT whole milk and UHT orange juice were inoculated at a concentration of approximately 7.0 log (CFU/ml) and pressurized with a dual valve UHPH machine at 300 MPa at the primary homogenising valve and at 30 MPa on the secondary valve. Viable and injured bacterial counts were measured 2 h after UHPH treatment and after 3, 6, and 9 days of storage at 4 °C for milk, and after 3, 6, 9, 12, and 15 days of storage at 4 °C for orange juice. The inlet temperature, the food matrix and the kind of strain influenced significantly (P < 0.05) the lethality level, which was higher for S. aureus in whole milk at an inlet temperature of 20 °C. No sublethal injuries were detected after treatments. The change over time of viable counts for both strains showed a very strong decreasing tendency during the storage at 4 °C for orange juice, while the strain S. carnosus showed a low decreasing tendency and greater resistance when inoculated in milk and pressurized at 6 °C.     

Effects of Zataria multiflora Boiss. essential oil and nisin on Bacillus cereus ATCC 11778

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO, 0.0%, 0.005%, 0.015%, 0.03% and 0.045%) and nisin (N, 0.0, 0.25, 0.5, 1.5 and 2.5 μg ml⁻¹), pH values (7.4, 6.5 and 6.0), temperatures (Ts, 10, 20 and 30 °C) and storage times (Ds, up to 43 days) on log₁₀ probability percentage of growth initiation (log P%) of one vegetative cell of Bacillus cereus in brain heart infusion broth were evaluated in a factorial design study. The log P% of the organism was significantly affected (P < 0.01) by the values of EO, N, pH, T and D.The combinations of T ⩾ 20 °C, EO ⩽ 0.03% and pH values (7.4, 6.5 and 6.0) could not obviously affect the growth of the organism in this study. Whereas, the strong inhibitory action was observed by increasing EO concentration to 0.045 at T ⩾ 20 °C and selected pH values (7.4, 6.5 and 6.0) and by decreasing temperature to 10 °C at EO ⩾ 0.015% and pH values used in this study. The inhibitory effect of N also was enhanced by decreasing storage temperature to 10 °C at the selected pH values (7.4, 6.5 and 6.0) in this study.The growth of the organisms was strongly affected by increasing EO concentration to 0.03% in combination with N concentrations used at the selected temperatures in this study. The growth of the organism was completely inhibited at combinations EO ⩾ 0.015%, N ⩾ 1.5 μg ml⁻¹, T ⩽ 30 °C and pH ⩽ 7.4 during 43 days of storage in this study. This synergistic effect of EO and N was enhanced in lower pH values (6.5 and 6.0) in the present study. The growth of organism was completely inhibited at combinations of EO ⩾ 0.005 and N ⩾ 1.5 μg ml⁻¹ at pH = 6.0, and EO ⩾ 0.03 and N ⩾ 0.5 μg ml⁻¹ at pH ⩽ 6.5 during the study at the selected Ts (30, 20 and 10 °C).     

Antimicrobial activity of malic acid against Listeria monocytogenes,Salmonella Enteritidis and Escherichia coli O157:H7 in apple,pear and melon juices

Minimal inhibitory (MIC) and minimal bactericidal (MBC) concentrations of malic acid against Listeria monocytogenes, Salmonella Enteritidis and Escherichia coli O157:H7 inoculated in apple, pear and melon juices stored at 5, 20 and 35 °C were evaluated. MICs and MBCs against L. monocytogenes, S. Enteritidis and E. coli O157:H7 were significantly affected by storage temperature, juice characteristics and type of microorganism. Malic acid was more effective at 35 and 20 °C than at 5 °C in all studied fruit juices. E. coli O157:H7 was more resistant to malic acid than S. Enteritidis and L. monocytogenes. Apple, pear and melon juices without malic acid were inhibitory to E. coli O157:H7, S. Enteritidis and L. monocytogenes at 5 °C, whereas, MBCs of 1.5% (v/v) of malic acid in apple and pear juices, and 2% (v/v) in melon juice at 5 °C were needed to reduce E. coli O157:H7, those concentrations being higher than those required to reduce S. Enteritidis and L. monocytogenes in those fruit juices. In addition, concentrations of 2%, 2.5% and 2.5% (v/v) of malic acid added to apple, pear and melon juices, respectively, were required to inactivate the three pathogens by more than 5 log cycles after 24 h of storage at 5 °C. Transmission electron microscopy showed that malic acid produced damage in the cell cytoplasm of pathogens without apparent changes in the cell membrane.     

Effect of combined physico-chemical treatments based on enterocin AS-48 on the control of Listeria monocytogenes and Staphylococcus aureus in a model cooked ham

Enterocin AS-48 was tested alone or in combination with chemical preservatives and/or heat against Listeria monocytogenes and Staphylococcus aureus in a cooked ham model system. AS-48 (20, 40 and 60 μg g⁻¹) alone was active against L. monocytogenes at 5 and 15 °C, but it was not sufficient to avoid regrowth of Listeria during the 60 days storage. Combination of AS-48 (40 μg g⁻¹) with nitrite/nitrate, pentasodium tripolyphosphate, sodium benzoate or potassium sorbate improved the anti-listeria effect during storage at 5 °C. The most effective combination was AS-48-nitrite/nitrate (0.007%) that reduced listeria below detection level from the beginning to end of storage. Although much more resistant, S. aureus was also inhibited by AS-48 alone at 5 °C, and especially in combinations with nitrite/nitrate, pentasodium tripolyphosphate, sodium lactate and sodium acetate. Best results against both pathogens were obtained when sodium pyrophosphate was applied in combination with 60 μg g⁻¹ AS-48. Sub-lethal heat (60 °C, 2 min) clearly increased AS-48 activity against both Listeria and Staphylococcus.     

Effects of gamma irradiation and frozen storage on microbial,chemical and sensory quality of chicken meat in Iran

Irradiation is considered one of the most efficient technological processes for the reduction of microorganisms in food. It can be used to improve the safety of food products, and to extend their shelf lives. The aim of this study was to evaluate the effects of gamma irradiation and frozen storage as a combination process for improvement of chicken meat shelf life. Broiler chicken were treated with 0 (non irradiated), 0.75, 3.0, and 5.0 kGy of gamma irradiation and held frozen for 9 months. The control and irradiated samples were stored at −18 °C and underwent microbial analysis, chemical characteristics and sensory evaluation at 3 months intervals. Microbial analysis indicated that irradiation and freezing storage had a significant effect (P < 0.05) on the reduction of microbial loads. There was no significant difference in sensory quality and chemical characteristics during freezing storage in chicken meat. The combination of frozen storage plus irradiation resulted in greater overall reductions on microbial loads, extending shelf-life of chicken meat for commercial application and critical condition.