Fermentation of Cucumbers in Anaerobic Tanks

A procedure was developed and tested for fermentation of cucumbers at low concentrations of NaCl in experimental, anaerobic tanks. The procedure included washing of the cucumbers, use of a buffered cover brine composed of 0.045M calcium acetate, sodium chloride to equilibrate at 2.7% or 4.6%, Lactobacillus plantarum culture, and N₂ purging to remove dissolved CO₂. The fermentations were predominantly homofermentative, lactic acid accounting for 95% of the cucumber sugars fermented. Firmness retention of the fermented cucumbers during storage for 1 year was improved by heating packaged products to 69°C before storage, but firmness retention was acceptable in un-heated products.     

The microbial safety of strawberry and raspberry fruits packaged in high-oxygen and equilibrium-modified atmospheres compared to air storage

Microbial safety of strawberry and raspberry fruits was assessed after shelf‐life extension by two new packaging systems, high‐oxygen atmospheres (HOA) and equilibrium‐modified atmospheres (EMA), in combination with an ethylene absorbing film. Both fruits had a shelf‐life of 3 days at 7 °C when macroperforated films were used. Strawberry fruits were acceptable for 5 days in both packages, raspberries had a shelf‐life of 7 and 5 days when using EMA and HOA respectively. Escherichia coli, Salmonella spp. and Listeria monocytogenes were artificially inoculated onto packaged fruits. All were able to survive on packaged fruits stored at 7 °C. Raspberries showed an enhanced inactivation of Salmonella during storage time in both types of packaging. Growth of L. monocytogenes was observed on the calyx of strawberries after the end of the established shelf‐life. Generally, increasing the shelf‐life of the fruits with EMA and HOA did not give an increased microbial risk.     

Coliphage as an indicator of fecal contamination in hydroponic cucumber (Cucumis sativus L) greenhouses

A preliminary study has been performed to evaluate the utility of somatic and F⁺‐specific coliphage as quality indicators of irrigation water used in hydroponic cucumber greenhouse operations. Samples of incoming water, waste hydroponic solution, cucumber fruit and plant roots derived from two greenhouses were screened for bacterial fecal indicators (generic Escherichia coli, fecal coliforms, total coliforms and Clostridium perfringens) and coliphage. Bacterial fecal indicators were present in incoming water and in spent hydroponic solution with coliphage only being sporadically recovered. However, both somatic and F⁺‐specific coliphage were consistently recovered from the roots of cucumber plants along with bacterial fecal indicators. Despite the heavy contamination of plant roots, the cucumber fruits were within acceptable microbiological limits. F⁺‐specific coliphage was recovered from 1 out of 25 cucumbers tested along with generic E coli. In contrast, no somatic coliphage was recovered from cucumbers despite coliforms being present on 15 out of 25 units. In conclusion, coliphage represents a poor index of hydroponic irrigation water quality but presence on cucumber fruit and roots can be used to highlight the presence of fecal indicator bacteria within greenhouse operations. Copyright © 2005 Society of Chemical Industry     

Conditioning Cucumbers to Increase Heat Resistance in the EFE System

The ethyiene-forming enzyme system (EFE) in cucumber fruit (Cucumis sativus L. cv. Burpee Hybrid II) developed an increased tolerance to hot water immersions of 30 to 60 min at 45°C and 30 to 50 min at 46°C when conditioned at 32.5 ± 0.5°C in air for 24 hr. Thermodynamic analysis of the heat inactivation of the ethyiene-forming enzyme (EFE) system in conditioned and unconditioned cucumbers showed: Increased D-value in the heat resistant EFE of conditioned cucumbers; larger energies of activations and Q₁₀ for conditioned cucumbers; larger entropy and enthalpy changes in conditioned cucumbers. The EFE system in conditioned cucumbers was in a more ordered state than in control cucumbers which was speculated to be due to the formation of hydrophobic bonds during conditioning thereby increasing the thermostability of the EFE system.     

Residue content of carbaryl applied on greenhouse cucumbers and its reduction by duration of a pre‐harvest interval and post‐harvest household processing

BACKGROUND: Carbaryl is widely used to control various insect pests on greenhouse cucumbers in Iran. Therefore the control of residual levels of this insecticide is highly necessary. The effects of the household processing such as washing, peeling and refrigeration storage, at 4 °C for 2 days on the reduction of residue levels in the plant tissues were investigated in the different groups. Samples were collected at 1 h to 14 days after application and analysed to determine the content and dissipation rate of carbaryl. Analysis was carried out by the QuEChERS method using HPLC‐UV. RESULTS: Carbaryl residue in samples, which were collected post‐application in different times showed a gradual and significant (P < 0.05) decrease. The half‐life (t_1/2) of carbaryl applied on cucumbers was 3.2 days. Carbaryl residues were detected in concentration ranges of 0.22–4.91 mg kg^?1. Also, the results indicated that the consumable safety time of carbaryl was found to be more than 14 days on cucumber. CONCLUSION: Household processing, such as washing and peeling and refrigeration storage, was effective in reducing the residue levels. Also, peeling was the most effective way to reduce the carbaryl residues of the cucumber samples. Washing and refrigerated storage also decreased carbaryl residues. Copyright © 2010 Society of Chemical Industry     

Chicken fillets subjected to UV‐C and pulsed UV light: Reduction of pathogenic and spoilage bacteria,and changes in sensory quality

We have compared the efficacy of continuous ultraviolet (UV‐C) (254 nm) and pulsed UV light in reducing the viability of Salmonella Enteritidis, Listeria monocytogenes, Staphylococcus aureus, enterohemorrhagic Escherichia coli, Pseudomonas spp., Brochothrix thermospacta, Carnobacterium divergens, and extended‐spectrum β‐lactamase producing E. coli inoculated on chicken fillet surface. Fluences from 0.05 to 3.0 J/cm² (10 mW/cm², from 5 to 300 s) used for UV‐C light resulted in average reductions from 1.1 to 2.8 log cfu/cm². For pulsed UV light, fluences from 1.25 to 18.0 J/cm² gave average reductions from 0.9 to 3.0 log cfu/cm². A small change in the odor characterized as sunburnt and increased concentration of volatile compounds associated with burnt odor posed restrictions on the upper limit of UV treatment, however no sensory changes were observed after cooking the meat. Treatments under modified atmosphere conditions using a UV permeable top film gave similar or slightly lower bacterial reductions.

Practical applications

Ultraviolet (UV) light may be used for decontaminating the surface of food products and reduce viability of pathogenic and spoilage bacteria. Exposure of raw chicken fillet surface to various doses of continuous UV‐C or pulsed UV light proposed in the present work represent alternatives for microbiological improvement of this product. Chicken fillets can be treated in intact packages covered with UV permeable top film, thus avoiding recontamination of the meat. UV‐C light treatment is a low cost strategy with low maintenance, whereas pulsed UV light involves more elaborate equipment, but treatment times are short and less space is required. Both methods can be helpful for producers to manage the safety and quality of chicken fillets.     

Microbial inactivation and quality improvement of tomatoes treated by package film with allyl isothiocyanate vapour

In‐package sanitisation was developed using polylactic acid (PLA) films with allyl isothiocyanate (AIT) vapour. Tomatoes were artificially inoculated with Escherichia coli, Geotrichum candidum and Fusarium oxysporum and stored in clamshell boxes with the film fixed to the underside of the lid. The changes in bacterial and fungal populations and the quality of tomatoes during storage at 4 and 10 °C were evaluated. The results revealed that the film treatment (4 × 8 cm² film in 1 L box) reduced the populations of inoculated bacteria and fungi on tomatoes by 2–3 log CFU g^?1, and then significantly (P < 0.05) inhibited their growth during the 21‐day storage period at both temperatures. Tomatoes subject to film treatment had fewer changes in quality (colour, firmness, contents of total soluble solid, titratable acids and vitamin C) than the control samples during storage. The antimicrobial PLA film can be used for in‐package sanitisation to extend the shelf‐life of packaged tomatoes or similar perishable vegetables.     

Storage studies of tomato and bell pepper using eco‐friendly films

Tomato (Lycopersicon esculentum) and bell pepper (Capsicum annuum), packaged in cartons (approximately 0.35 kg per box) covered with either eco‐friendly chitosan film or synthetic petroleum‐based low‐density polyethylene (LDPE) film, were stored at room temperature (27 ± 1 °C) and 65 ± 3% relative humidity (RH). Fruits were withdrawn periodically and changes in physico‐chemical, instrumental and sensory characteristics were analysed. During storage, oxygen levels showed only marginal changes, while CO₂ levels showed a gradual increase, especially so in LDPE film‐covered cartons. The fresh weight loss, colour, firmness, formation of defective spots and shrivelling showed greater changes for unpackaged fruits as well as for those in LDPE film‐covered cartons, in comparison with fruits stored in chitosan film‐covered cartons, which retained many of the desirable attributes. Principle component analysis of data from sensory or instrumental sensory analyses indicated segregation of samples stored under different conditions with respect to both desirable and undesirable attributes. The fruits showed greater deterioration, including the loss of characteristic bell pepper odour, when packaged in cartons covered with LDPE films, while those packaged in chitosan film retained more of the desirable quality attributes for a longer period. Copyright © 2006 Society of Chemical Industry     

Effectiveness of antioxidant‐impregnated film in retarding lipid oxidation

The effectiveness of an antioxidant‐impregnated film to retard autoxidation of a packaged model product containing linoleic acid, via an evaporation/sorption mechanism, was evaluated as a function of storage time and temperature. The rate of loss of antioxidant from the package film structure was described by a first‐order expression. The first‐order rate constants were dependent on the initial concentration of antioxidant in the film. The rate of loss of 3,5‐di‐tert‐butyl‐4‐hydroxytoluene (BHT) from the package film structure was found to be much higher than the rate of loss of α‐tocopherol at both storage conditions (23 and 45 °C, 50% relative humidity) studied. A freeze‐dried model food product system was developed as the source for the autoxidation of linoleic acid in storage stability studies. The storage stability of this model food system packaged with antioxidant‐impregnated film pouches was evaluated. Hexanal as an index of oxidation from the model product system was collected by a dynamic purge and trap system and quantified by a gas chromatography/mass spectrometry procedure. The BHT‐impregnated laminate pouch showed a notable effectiveness in retarding lipid oxidation of the model product at 45 °C as a function of storage time. The control (non‐antioxidant) and α‐tocopherol‐impregnated laminate pouch structures showed no effect on retarding lipid oxidation of the model product during storage at 45 °C. Copyright © 2004 Society of Chemical Industry     

Effects of ultraviolet light and ultrasound on microbial quality and aroma-active components of milk

BACKGROUND: Heat treatment is the most common way to extend the shelf life of milk. However, alternative technologies such as ultraviolet (UV) light and ultrasound (US), which are non‐thermal methods for processing milk, have been developed to replace heat treatment. These technologies do not have any adverse effects on the quality of milk. The major purpose of this study was to investigate the effects of UV and US on different micro‐organism groups and aroma compounds in milk. RESULTS: Heat pasteurisation at 65 °C for 30 min was used as thermal control treatment. The growth of total coliform group bacteria, Escherichia coli and Staphylococcus spp. was completely reduced by UV treatment. Application of US was not sufficient to reduce the numbers of yeasts and moulds. In neutral/basic fractions, 3‐methylthiophene (plastic), hexanal (grass) and 1‐hexen‐3‐one (floral) were major volatiles in milk samples. CONCLUSION: UV had a major effect on total coliforms, E. coli and Staphylococcus spp., but US was not as effective as UV and heat treatment in reducing certain groups of micro‐organisms. No major differences were observed in terms of aroma‐active compounds and flavour of milk following the different treatments. However, some new volatiles and change in rheological properties were generated by UV and US treatments. Copyright © 2011 Society of Chemical Industry     

Survival of Escherichia coli O157:H7 in cucumber fermentation brines

Abstract: Bacterial pathogens have been reported on fresh cucumbers and other vegetables used for commercial fermentation. The Food and Drug Administration currently has a 5‐log reduction standard for E. coli O157:H7 and other vegetative pathogens in acidified pickle products. For fermented vegetables, which are acid foods, there is little data documenting the conditions needed to kill acid resistant pathogens. To address this knowledge gap, we obtained 10 different cucumber fermentation brines at different stages of fermentation from 5 domestic commercial plants. Cucumber brines were used to represent vegetable fermentations because cabbage and other vegetables may have inhibitory compounds that may affect survival. The 5‐log reduction times for E. coli O157:H7 strains in the commercial brines were found to be positively correlated with brine pH, and ranged from 3 to 24 d for pH values of 3.2 to 4.6, respectively. In a laboratory cucumber juice medium that had been previously fermented with Lactobacillus plantarum or Leuconostoc mesenteroides (pH 3.9), a 5‐log reduction was achieved within 1 to 16 d depending on pH, acid concentration, and temperature. During competitive growth at 30 °C in the presence of L. plantarum or L. mesenteroides in cucumber juice, E. coli O157:H7 cell numbers were reduced to below the level of detection within 2 to 3 d. These data may be used to aid manufacturers of fermented vegetable products determine safe production practices based on fermentation pH and temperature. Practical Application: Disease causing strains of the bacterium E. coli may be present on fresh vegetables. Our investigation determined the time needed to kill E. coli in cucumber fermentation brines and how E. coli strains are killed in competition with naturally present lactic acid bacteria. Our results showed how brine pH and other brine conditions affected the killing of E. coli strains. These data can be used by producers of fermented vegetable products to help assure consumer safety.     

The effects of natural antioxidants and lighting conditions on the quality of salmon (Salmo salar) fillets packaged in modified atmosphere

The effect of lighting conditions (darkness, a low‐UV colour‐balanced lamp and supermarket fluorescents), along with the application of natural antioxidants (rosemary extract and ascorbic acid) on shelf‐life of salmon (Salmo salar) fillets packaged in modified atmosphere and stored at 1 ± 1 °C was studied. Darkness and lighting with low‐UV colour‐balanced lamps led to an extension of shelf‐life compared with conventional light, as assessed by a* values, lipid oxidation (TBARS value) and sensory evaluation. The application of natural antioxidants on the surface of MAP salmon fillets gave rise to a delay of lipid oxidation as well as an improvement of the sensory quality, mainly in the case of conventional lighting conditions. Copyright © 2005 Society of Chemical Industry     

Effects of Salts and Preheating Temperature of Brine on the Texture of Pickled Cucumbers

The effects of salt type and preheating temperature on the texture and quality of pickled cucumber were studied. Four types of salt were used: bay salt, purified salt, and 2 prepared salts, 1 containing the same amount of Ca²⁺ and Mg²⁺ as those of bay salt, and the other containing a 3‐fold higher concentration of Ca²⁺ and Mg²⁺ than bay salt. Two different temperatures were used for the salt solutions: 98 °C and 65 °C. All samples were fermented for 30 d at 25 °C. To evaluate the quality of the pickled cucumber with fermentation, the pH level, total acidity, alcohol insoluble solids, and mineral contents were analyzed. Texture and sensory evaluation as well as a microscopic observation were performed to observe the textural change of the pickled cucumber during fermentation. Pickled cucumbers with 98 °C of preheated brine showed better texture than the ones with 65 °C. The pickled cucumbers brined with prepared salt, 1 which had the same amount of Ca²⁺ and Mg²⁺ to bay salt, displayed the best result among the samples tested, in terms of sensory, textural, and physical properties.     

Evaluation of Antibacterial Activity of Whey Protein Isolate Coating Incorporated with Nisin,Grape Seed Extract,Malic Acid,and EDTA on a Turkey Frankfurter System

ABSTRACT: The effectiveness of whey protein isolate (WPI) coatings incorporated with grape seed extract (GSE), nisin (N), malic acid (MA), and ethylenediamine tetraacetic acid (EDTA) and their combinations to inhibit the growth of Listeria monocytogenes, E. coli O157:H7, and Salmonella typhimurium were evaluated in a turkey frankfurter system through surface inoculation (approximately 10⁶ CFU/g) of pathogens. The inoculated frankfurters were dipped into WPI film forming solutions both with and without the addition of antimicrobial agents (GSE, MA, or N and EDTA, or combinations). Samples were stored at 4 °C for 28 d. The L. monocytogenes population (5.5 log/g) decreased to 2.3 log/g after 28 d at 4 °C in the samples containing nisin (6000 IU/g) combined with GSE (0.5%) and MA (1.0%). The S. typhimurium population (6.0 log/g) was decreased to approximately 1 log cycles after 28 d at 4 °C in the samples coated with WPI containing a combination of N, MA, GSE, and EDTA. The E. coli O157:H7 population (6.15 log/g) was decreased by 4.6 log cycles after 28 d in samples containing WPI coating incorporated with N, MA, and EDTA. These findings demonstrated that the use of an edible film coating containing nisin, organic acids, and natural extracts is a promising means of controlling the growth and recontamination of L. monocytogenes, S. typhimurium, and E. coli O157:H7 in ready‐to‐eat poultry products.     

USE OF FLEXIBLE POLYMER MATERIAL FOR PACKAGING FRESH PEACHES

Fresh peaches (Prunus persica) were overwrapped in trays with 1 of 3 formulations of flexible polyvinyl chloride (PVC) film that differed in gas transmission rate or they were held in nonwrapped trays (controls). The CO₂ transmission rate at 0°C for PVC type III film was 280 mL/m^2. h (1 atmos); that of type II was 4 times greater and that of type I, about 5 times greater. The peaches were stored either 14 days at 0° or 7.5°C, or 7 days each at 0° and 7.5°C plus 2 days at 20°C to simulate retail display. The mean CO₂ levels were 10, 7.2 and 4.7% in packages that were wrapped with PVC III film and held at 7.5°, 0°/7.5° and 0°C, respectively. CO₂ in packages wrapped with PVC I or II was below 3% at each storage temperature. O₂ concentration remained about 4% in all packages. Weight loss was less and fruit was firmer among those packaged in PVC III than among nonwrapped controls at each of the 3 storage temperatures. Storage temperature had no effect on weight loss or of fruit held in PVC III film. External appearance of fruit packaged with the 3 types of film was significantly better than that of the controls. Internal appearance of the peaches was unaffected by any of the treatments. A microatmosphere favorable for fresh peaches can be maintained within packages overwrapped with polymer films that are selectively permeable to respiratory gases.     

Quality of enoki mushrooms as affected by packaging conditions

Fresh enoki mushrooms (100 g) were packaged under various conditions and stored at 10 °C for 14 days. Package atmosphere, weight loss, stipe elongation, surface colour and sensory quality of the mushrooms were measured during storage. Different levels of initial vacuum application did not have a significant influence on the in‐package atmosphere after 2 days. The half‐vacuum package was best in terms of quality preservation of the fresh mushrooms. A polyolefin film with respective gas permeabilities of 166 and 731 ml m⁻² h⁻¹ atm⁻¹ to O₂ and CO₂ established an equilibrated atmosphere of 1.7–2.4% O₂ and 4.1–5.6% CO₂ inside the package at 10 °C. This polyolefin film was shown to contribute to preserving the freshness of the mushrooms. Temperature fluctuations between 5 and 15 °C did not induce a harmful atmosphere inside the polyolefin package, though high temperatures accelerated the quality loss. © 2000 Society of Chemical Industry     

Ultraviolet and Pulsed Electric Field Treatments Have Additive Effect on Inactivation of E. coli in Apple Juice

ABSTRACT: Apple juice inoculated with Escherichia coli ATCC 23472 was processed continuously using either ultraviolet (UV), high‐voltage pulsed electric field (PEF), or a combination of the PEF and UV treatment systems. Apple juice was pumped through either of the systems at 3 flow rates (8, 14, and 20 mL/min). E. coli was reduced by 3.46 log CFU/mL when exposed in a 50 cm length of UV treatment chamber at 8 mL/min (2.94 s treatment time with a product temperature increase of 13 °C). E. coli inactivation of 4.87 log CFU/mL was achieved with a peak electric field strength of 60 kV/cm and 11.3 pulses (average pulse width of 3.5 μs, product temperature increased to 52 °C). E. coli reductions resulting from a combination treatment of UV and PEF applied sequentially were evaluated. A maximum E. coli reduction of 5.35 log CFU/mL was achieved using PEF (electrical field strength of 60 kV/cm, specific energy of 162 J/mL, and 11.3 pulses) and UV treatments (length of 50 cm, treatment time of 2.94 s, and flow rate of 8 mL/min). An additive effect was observed for the combination treatments (PEF and UV), regardless of the order of treatment (P > 0.05). E. coli reductions of 5.35 and 5.30 log CFU/mL with PEF treatment (electrical field strength of 60 kV/cm, specific energy of 162 J/mL, and 11.3 pulses) followed by UV (length of 30 cm, treatment time of 1.8 s, and flow rate of 8 mL/min) and UV treatment followed by PEF (same treatment conditions), respectively. No synergistic effect was observed.     

Development of an Effective Treatment for A 5‐Log Reduction of Escherichia coli in Refrigerated Pickle Products

Refrigerated cucumber pickle products cannot be heat processed due to the loss of characteristic sensory attributes. Typically brined refrigerated pickles contain less than 100 mM acetic acid with pH values of 3.7 to 4.0. Refrigeration (4 to 10 °C) helps to inhibit the growth of spoilage bacteria and maintain flavor, texture, and appearance of the pickles. Previous research has shown that pathogenic Escherichia coli strains are unusually acid resistant and survive better in refrigerated acid solutions than at higher temperatures. We found that E. coli O157:H7 can survive for 1 mo or longer at 4 °C in brines typical of commercial refrigerated pickles. Our objective was to develop methods to assure a 5‐log reduction of pathogenic E. coli in these types of products, while maintaining the sensory characteristics. A novel brine formulation was developed, based on current commercial refrigerated pickle brines, which contained 25 mM fumaric acid, 5 mM benzoic acid, 70 mM acetic acid, and 342 mM (2%) sodium chloride, with a pH of 3.8. Sensory data indicate that this formulation did not affect flavor or other sensory attributes of the product, compared to traditional formulations. We achieved a 5‐log reduction of E. coli O157:H7 at 30 °C for 1.52 ± 0.15 d, at 20 °C for 3.12 ± 0.34 d, or at 10 °C for 8.83 ± 0.56 d. Growth of lactic acid bacteria was also inhibited. These results can be used by manufacturers to assure a 5‐log reduction in cell numbers of E. coli O157:H7 and Salmonella without a heat process during the manufacture of refrigerated pickle products. Practical Application : While refrigerated acidified vegetable products are exempt from the acidified foods regulations, we have shown that the vegetative microbial pathogens E. coli O157:H7 can survive for up to 1 mo in these products, given current commercial production practices. To improve the safety of refrigerated pickle products, a brine formulation with reduced acetic acid, but containing fumaric acid, was developed to assure a 5‐log reduction in cell numbers of E. coli O157:H7 without a heat process. The formulation can be used to assure the safety of refrigerated pickled vegetables without altering sensory characteristics.     

Control of Listeria monocytogenes in Vacuum-Packaged Pre-Peeled Potatoes

Growth of Listeria monocytogenes on the surface of fresh peeled potatoes, treated with sulfite or a commercial browning inhibitor (CBI), packaged under vacuum and stored at 4,15 and 28°C was determined. At 4°C, L. monocytogenes did not grow in all treated potatoes even after 21 days. At 15°C, L. monocytogenes grew to 7 log₁₀ CFU/g within 12 days in the potatoes treated with sulfite or CBI. At 28°C, L. monocytogenes population was greater than 3 log₁₀ CFU/g by 24 h in all samples regardless of treatment. Sulfites or a CBI appeared to provide a measure of safety in pre-peeled potatoes packaged under vacuum when kept at proper refrigeration temperatures.     

UV Inactivation of E. coli in Liquid Egg White

Liquid egg white is currently pasteurized using heat; however, this treatment damages the functional properties of the egg. In this study, a nonthermal ultraviolet light (UV) system was developed to pasteurize liquid egg white. The system consisted of low-pressure mercury bulbs surrounded by UV transparent tubing. Egg white was inoculated with Escherichia coli K12 and pumped through the UV system at a flow rate of 330 ml/min. The effects of treatment time (0 to 160 s), temperature (30 to 50 °C), and egg white pH (7 to 9) on the inactivation of E. coli were investigated. The population of E. coli in egg white was reduced by 4.3 log after being exposed to UV at 50 °C for 160 s. Inactivation was linearly dependent on treatment time and was adequately described using first-order kinetics (r ² of 0.94). The electrical energy of the process was calculated to be 44 J/ml. Inactivation was directly dependent on temperature and inversely dependent on pH. Nonthermal UV processing has the potential to improve the safety and functional properties of liquid egg white. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.