Microbial profile of buffalo sausage during processing and storage

A study was made on the microbial levels of buffalo sausage during preparation and storage at 4 ± 1 °C. Microbial counts in raw minced meat were, total plate count (TPC) (log cfu/g) 5.41 ± 0.25; coliforms (MPN/g) 23.2; Staphylococcus aureus (log cfu/g) 1.57 ± 0.11; yeasts and molds (log cfu/g) 2.29 ± 0.07 and lactic acid bacteria (LAB) (log cfu/g) 0.60 ± 0.20. Sausage emulsion showed similar trend in microbial counts with minimal microbial contamination during the preparation of emulsion. Cooked buffalo sausage gave the following microbial counts: TPC (log cfu/g) 3.75 ± 0.31; coliforms (MPN/g) 0.2; LAB (log cfu/g) 0.07 ± 0.01; yeast and molds (log cfu/g) 0.72 ± 0.07. S. aureus, Clostridium perfringens and Bacillus cereus were not detected in cooked sausages. These results indicate that steam cooking for 45 min followed in the study was effective in reducing the microbial counts substantially. The investigation revealed that shelf life of cooked buffalo sausage was 31 days in either vacuum or CO₂ at 4 ± 1 °C. The results indicated that spoilage of vacuum packed cooked buffalo sausage was likely due to LAB while microflora other than LAB may be responsible for spoilage of CO₂ packed cooked buffalo sausage. The study suggests that measures such as low initial microbial counts, hygienic precautions during preparation of sausage, steam cooking for 45 min, vacuum or CO₂ packing and storage at 4 ± 1 °C would control the microbial growth and provide wholesomeness and safety to the buffalo sausage.     

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.     

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.     

Effect of an argon-containing packaging atmosphere on the quality of fresh pork sausages during refrigerated storage

The effects of modified atmosphere packaging (MAP) with commercial gas mixtures made up of either CO₂ and argon or CO₂ and nitrogen on the microbiological and physico-chemical characteristics of fresh pork sausages during refrigerated storage were studied and the results compared with vacuum and over-wrap packaging. The presence of argon in the mixture of gases barely affected the growth of enterobacteria, which were at their lowest levels (P < 0.05) at the end of the preservation period. MAP with argon did not affect (P > 0.05) lactic acid bacteria or total viable counts in samples with N₂. The biogenic amine levels in all the samples remained low during storage with the exception of spermidine and spermine. There were no significant differences between the two lots in MAP respecting color parameters. MAP with argon and CO₂ had a beneficial effect on sensorial evaluation during the 28 days storage period, when compared with that of the control, which was rejected after 11 days of storage.     

Emerging sanitizers and Clean Room packaging for improving the microbial quality of fresh-cut ‘Galia’ melon

This study evaluated how traditional or new sanitizers, alone, or in combination with the use of a Clean Room (CR), affected the respiration rate, microbial, nutritional and sensorial quality of fresh-cut ‘Galia’ melon. Melon pieces were packed in polypropylene trays under passive modified atmosphere (7.4 kPa O₂ + 7.4 kPa CO₂) and stored up to 10 days at 5 °C. The following treatments were performed: 150 mg/l chlorine (control) for 1 min; 80 mg/l peracetic acid (PAA) for 1 min; ozonated water (0.4 mg/l) for 3 and 5 min. The combinations of: ozonated water and PAA; 150 mg/l chlorine and packaging in CR; ozonated water for 3 min and package in CR; ozonated water for 3 min + PAA and packaging in CR were also studied. Throughout the shelf-life psychrotrophic, mesophilic, Enterobactericeae, lactic acid bacteria, moulds and yeast growth were determined. The use of PAA provided the lowest microbial load, but this sanitizer decreased the total vitamin C and the antioxidant activity. Nevertheless, the combination of PAA with 0.4 mg/l of ozonated water (3 min) could be a good substitute of use of chlorine. This treatment was effective in reducing the microbial counts, maintaining the antioxidant compounds and respiration rate and maintained the sensorial quality of the product during the 10 days at 5 °C. Treated product packaged in a CR did not show increased treatment effect, probably due to air quality in the laboratory. The use of CR just for the packaging of the melon pieces did not offer any additional advantage. However, the utilization of CR in an industrial environment during all processing steps (from washing to packaging) should be investigated for potential benefits.     

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.     

Effect of organic acids,hydrogen peroxide and mild heat on inactivation of Escherichia coli O157:H7 on baby spinach

Minimally processed baby spinach contaminated with Escherichia coli O157:H7 has been associated with multiple outbreaks of foodborne illnesses recently. Chlorinated water is widely used to wash vegetables commercially, but this washing procedure has limited efficacy and can lead to the formation of carcinogenic substances. This study was conducted to determine the effects of organic acids and hydrogen peroxide alone and in binary combinations with or without mild heat (40 and 50 °C) on the inactivation of Escherichia coli O157:H7 on baby spinach. Baby spinach leaves were dip-inoculated with E. coli O157:H7 to a level of 6 log CFU/g and stored at 4 °C for 24 h before treatment. Individual washing solutions (1% and 2% lactic acid [LA], citric acid [CA], malic acid [MA], tartaric acid [TA], acetic acid [AA], hydrogen peroxide [H₂O₂] as well as binary combinations of LA, CA, MA and H₂O₂ at final concentrations of 1% were used to decontaminate spinach leaves at 22, 40 or 50 °C for 2–5 min to test their efficacy in reducing E. coli O157:H7. Chlorinated water (200 ppm free chlorine) decreased the population of E. coli O157:H7 on baby spinach by only 1.2–1.6 log CFU/g, which was not significantly different from DI water washing. Washing with 1% LA at 40 °C for 5 min was the most effective treatment achieving a 2.7 log reduction of E. coli O157:H7 which is significantly higher than chlorine washing. Washing with LA + CA or LA + HP at 40 °C for 5 min was equally effective against E. coli O157:H7, resulting in a 2.7 log reduction of E. coli O157:H7. The application of mild heat significantly enhanced the efficacy of washing solutions on the inactivation of E. coli O157:H7. There was, however, no significant difference between treatments at 40 °C for 5 min and 50 °C for 2 min. The results suggested that the use of organic acids in combination with mild heat can be a potential intervention to control E. coli O157:H7 on spinach.     

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.     

Microbial shelf-life extension of chilled Coho salmon (Oncorhynchus kisutch) and abalone (Haliotis rufescens) by high hydrostatic pressure treatment

This study was carried out to evaluate the effect of high hydrostatic pressure (HHP) treatment on microbial behavior and the shelf-life extension of Coho salmon and abalone during chilled storage at 4 °C. For salmon, HHP treatments were applied at 135, 170, and 200 MPa for 30 s, while abalone treatment consisted of 500 MPa for 8 min and 550 MPa for 3 or 5 min. Spoilage bacteria (Pseudomonas spp. and hydrogen sulfide-producing bacteria, mainly Shewanella putrefaciens), as well as aerobic mesophilic and psycrophilic microorganisms, were enumerated immediately after treatment and throughout subsequent storage at 4 °C. Results have shown that HHP treatment reduced the initial microbial counts of salmon from 3.16 to 2.2 log units, moreover abalone was reduced from 1.3 log to undetectable levels (<10 CFU g⁻¹). HHP-treatment used for salmon were not sufficient to extend their shelf-life. However, the shelf-life of abalone was extended from 30 (control samples) to >65 days irrespective of HHP treatment applied.     

Active film incorporated with sorbic acid on pastry dough conservation

Antimicrobial films, 25 and 70 μm-thick, incorporated with 0–6% of sorbic acid, were produced and layered with pastry dough without preservative to evaluate its antimicrobial action. Control pastry dough containing sorbate potassium was layered with low-density polyethylene films (LDPF). The sandwiches (films/pastry dough) were stored in LPDF bags at 8 ± 1 °C. The results of microbiological analyses obtained in the initial time for pastry dough with or without additive complied with the standards of the Brazilian current legislation. After 40 days of storage, the pastry dough layered with 70 μm-thick films, containing 3–6% of sorbic acid had significantly smaller microbial growth than, or equivalent to, the control pastry dough. Pastry dough with 25 μm-thick films, containing 6% sorbic acid, had the psychrotrophic count inferior to the control, and the aerobic mesophilic Staphylococcus spp. counts were 1 log cycle superior. The water activity and the moisture level showed no differences between the treatments throughout the storage time.     

Combined effects of chemical dip and/or carrageenan coating and/or controlled atmosphere on quality of fresh-cut banana

The combined effect of chemical dip and/or edible coating and/or controlled atmosphere (CA) on quality of fresh-cut banana was investigated. Banana slices were subject to a 3-min dip into a solution containing 1% (w/v) calcium chloride, 0.75% (w/v) ascorbic acid and 0.75% (w/v) cysteine and/or combined with a carrageenan coating and/or combined with controlled atmosphere (3% O₂ + 10% CO₂). Physico-chemical and microbiological qualities were evaluated during 5 days of storage at 5 °C. Dip combined with CA treatment prevented product weight loss and increase of polyphenol oxidase activity during the 5 days of storage. Colour, firmness, pH, tritatable acidity and total soluble solids values and total phenolic content presented the smallest changes. Microbial analysis showed that minimally processed bananas were within the acceptable limits during 5 days of storage at 5 °C.     

Removing of central nervous tissues from dressed carcasses: Washing with a low concentration of lactic acid in spraying cabinet

The efficiency of using lactic acid (LA) as a surface decontaminator for carcasses contaminated with spinal chord (SC) tissues was evaluated. Four representative places with surface area of 5 × 5 cm, were marked on the inner side of the porcine carcasses. 0.200 μl of 0.5% SC solution was applied to each marked area and separately washed in a specially designed spraying cabinet, which comprises 15 nozzles adjusted to spray 1% LA or tap water with a scatter pressure of 0.49 MPa. Samples were collected after washing for 15, 30, 60 and 90 s and analyzed by Ridascreen kit ELISA test. 1% LA reduces the SC materials to pre-contaminated levels while having negligible effect on the color of carcasses. Furthermore washing with LA insignificantly reduced the total microbial counts. Using very low concentration of LA (1%) in production lines of slaughter houses may help to decontaminate the carcasses to some extent without having adverse impact on quality attributes.     

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 effect of packaging conditions on the quality of minimally processed celeriac flakes

The aim of the study was to select packaging conditions of minimally processed celeriac to preserve their quality during storage for 12 days at 4 and 15 °C. The quality of the product was determined on the basis of colour measured in the CIE L¹a¹b¹ system, sensory quality and total counts of mesophilic and psychrophilic bacteria, counts of moulds and yeasts, coliform counts, counts of Pseudomonas bacteria and the presence of bacteria from the genus Clostridium perfringens. Moreover, changes were determined in oxygen and carbon dioxide contents in the atmosphere within the packs, in which the product was stored. Celeriac flakes were packaged in the atmosphere with varying CO₂ contents (0%, 5%, 10%, 20%, 30%, 50% plus 2% O₂ and with balance N₂). After 12 days at 4 °C, it was found that celeriac flakes packaged in atmosphere containing 5% or 10% CO₂, 2% O₂ and balance N₂ were characterized by better quality than samples packaged in air atmosphere or in the atmosphere with CO₂ contents of 0% or higher than 10%. Modified atmosphere with the content of 5% or 10% CO₂, 2% O₂ and balance N₂, applied in the packaging of celeriac flakes, resulted in the inhibition of growth of mesophilic, psychrophilic and coliform bacteria in the tested minimally processed product.     

Safe and shelf-stable natural casing using hurdle technology

Safe and shelf-stable natural casing were prepared using a combination of hurdles viz. reduced water activity, packaging and gamma irradiation. Washed lamb intestines were treated with common salt to reduce water activity to 0.80 ± 0.02, packed in polyethylene bags and subjected to gamma-irradiation (5 and 10 kGy). Control non-irradiated samples had high total viable counts (10⁶ CFU/g), aerobic spores (10³ CFU/g), spores of sulphite reducing clostridia (10³ CFU/g), potentially pathogenic bacteria such as staphylococci (10⁴ CFU/g) and coliforms (10² CFU/g). Treatment with gamma radiation resulted in a dose dependent reduction in counts of these microbes. A dose of 5 kGy was sufficient to reduce total viable counts by three log cycles; spore counts by two log cycles and completely eliminate staphylococci and coliforms. Samples subjected to a 10 kGy dose were devoid of any viable microbes. The reduced water activity of the product prevented growth of the microbes in natural casings during storage at room temperature. Sausages prepared using hurdle processed natural casing were examined for sensory and textural properties. It was observed that product acceptability and mechanical strength was not affected by radiation processing. Our studies indicated that shelf-stable and safe natural casing could be prepared using a combination of hurdles.     

Effect of packaging material headspace,oxygen and light transmission,temperature and storage time on quality characteristics of extra virgin olive oil

The effect of packaging parameters (transmission to light and oxygen, headspace volume) and storage temperature on quality characteristics of extra virgin olive oil (EVOO) was studied as a function of storage time (0–12 months). Packaging materials tested included clear glass, clear polyethylene terephthalate (PET), clear PET + UV blocker, clear PET covered with aluminum foil and clear polypropylene (PP) bottles. Quality parameters monitored over the 12 month storage period included: acidity, peroxide value (PV), spectrophotometric indices (K₂₃₂, K₂₇₀) and color. Results showed that the best packaging material for olive oil packaging was glass followed by PET. PP proved to be unsuitable for such an application. Exposure of olive oil samples to light, high storage temperatures (35 °C) and large headspace volumes caused substantial deterioration in product quality parameters. The most pronounced effect was that of temperature and light while the smallest effect was that of headspace volume and packaging material permeability to oxygen. Olive oil color was not substantially affected by storage conditions with the exception of storage of olive oil at 35 °C exposed to light for 12 months. Shelf life of extra virgin olive oil was 6 months packaged in clear glass in the dark at temperatures up to 22 °C; 3 months in clear PET in the dark at 22 °C and less than 3 months in clear PP in the dark at 22 °C. When exposed to light, shelf life of olive oil was 9 months when packaged in PET + aluminum foil; 3 months in PET + UV blocker and less than 3 months in clear PET at 22 °C. Product shelf life was less than 3 months at 35 °C. Finally oxygen in the headspace of olive oil resulted in deterioration of product quality. The relative contribution of parameters studied to the retention of olive oil quality was: temperature ≈ light > container headspace > packaging material oxygen permeability.     

Effect of gamma irradiation on Listeria ivanovii inoculated to iceberg lettuce stored at cold temperature

A low-dose gamma irradiation considerably reduced the total plate counts, psychrotrophic bacteria, lactic acid bacteria, and inoculated Listeria ivanovii on shredded iceberg lettuce. The total plate count of the lettuce irradiated at 1.0 kGy was reduced by 3.38 log₁₀ cfu/g on 0 storage day and to below the limit of detection (<2 log₁₀ cfu/g) as the cold storage was extended. Irradiation at 0.5 kGy effectively reduced the psychrotrophic bacterial counts and lactic acid bacterial counts in the lettuce to below the limit of detection (2 log₁₀ cfu/g). Irradiation at 1.0 kGy reduced L. ivanovii inoculated onto the shredded iceberg lettuce to below the limit of detection. The results showed that an irradiation at 1 kGy eliminates the bacterial contamination from the lettuce sample without any sensorial quality defect.     

Effect of potassium sorbate washing on the growth of Listeria monocytogenes on fresh poultry

This work evaluated the effect of potassium sorbate washing on the growth of Listeria monocytogenes on poultry legs stored at 4 °C for 7 days. Fresh inoculated chicken legs were dipped into either a 2.5% (w/v) or 5% potassium sorbate solution or distilled water (control). Changes in mesophiles, pychrotrophic counts and sensorial characteristics (odor, color, texture and overall appearance) were also evaluated.The shelf life of the samples washed with potassium sorbate was extended by at least 2 days over the control samples washed with distilled water. Legs washed with 5% potassium sorbate showed a significant (p < 0.05) inhibitory effect on L. monocytogenes compared to control legs, with a decrease of about 1.3 log units after 7 days of storage. Sensory quality was not adversely affected by potassium sorbate.     

Inactivation effect of newly developed low concentration electrolyzed water and other sanitizers against microorganisms on spinach

The efficacy of newly developed low concentration electrolyzed water (LcEW) was investigated to inactivate the pathogens on spinach leaves as a convenient and safe alternative sanitizer and it was compared to other sanitizers. Spinach leaves were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and dip treated with deionized water (DIW), LcEW, strong acid electrolyzed water (SAEW), aqueous ozone (AO), 1% citric acid (CA) and sodium hypochlorite solution (NaOCl) for 3 min at room temperature (23 ± 2 °C). For all pathogens, the similar pattern of microbial reduction on spinach was apparent with LcEW and SAEW washing. In the present study, it was found that LcEW inactivated, at maximum, 1.64–2.80 log cfu/g and DIW resulted in lowest reduction, 0.31–0.95 log cfu/g of background or pathogenic microflora present on spinach leaves compared to the unwashed control. The findings of this study indicate that LcEW and SAEW did not differ significantly (P > 0.05) in reducing background or pathogenic microflora on spinach and LcEW may be a promising sanitizer for washing vegetables without environmental pollution instead of using electrolyzed oxidizing (EO) water or SAEW.     

Validation studies on an online monitoring system for reducing faecal and microbial contamination on beef carcasses

The objective of this research was to establish the reduction in the incidence of carcass faecal contamination and microbial counts that could be achieved in a beef slaughter plant using a novel information technology based online monitoring system. On 18 separate visits over the course of 6 months, every carcass (approximately 500 per day) was examined at the final inspection stand for visible faecal contamination. Each incidence was attributed to dehiding or evisceration operations. On each visit, 10 carcasses were swabbed at the trimming stand, at the hock, rump, anus, brisket and flank to determine total viable counts (TVC), Escherichia coli counts (ECC), total enteric counts (TEC) and total coliform counts (TCC). Over the course of this study, faecal contamination rates for dehiding and evisceration were reduced from 54.2% to 28.2% and from 32.5% to 13.7%, respectively. TVC remained constant at approximately 3.0 log₁₀ cfu cm⁻² while ECC, TEC and TCC decreased by 0.56 log₁₀ cfu cm⁻², 0.83 log₁₀ cfu cm⁻² and 0.9 log₁₀ cfu cm⁻², respectively. Online monitoring is therefore an effective means of reducing the incidence of bovine carcass faecal and enteric counts.