Shelf-life of minimally processed cabbage treated with neutral electrolysed oxidising water and stored under equilibrium modified atmosphere

Minimally processed vegetables (MPV) have a short shelf-life. Neutral electrolysed oxidising water (NEW) is a novel decontamination method. The objective of this study was to test the potential of NEW to extend the shelf-life of a MPV, namely shredded cabbage. Samples of shredded cabbage were immersed in NEW containing 40 mg/L of free chlorine or tap water (control) up to 5 min, and then stored under equilibrium modified atmosphere at 4 degrees C and 7 degrees C. Proliferation of aerobic mesophilic bacteria, psychrotrophic bacteria, lactic acid bacteria and yeasts were studied during the shelf-life. Also pH and sensorial quality of the samples as well as O(2) and CO(2) composition of the headspace of the bags was evaluated. From the microbial groups, only psychrotrophic counts decreased significantly (P<0.05) due to the effect of NEW, but the counts in treated samples and controls were similar after 3 days of storage at 4 degrees C and 7 degrees C. Packaging configurations kept O(2) concentration around 5% and prevented CO(2) accumulation. pH increased from 6.1-6.2 to 6.4 during the shelf-life. No microbial parameter reached unacceptable counts after 14 days at 4 degrees C and 8 days of storage at 7 degrees C. The shelf-life of controls stored at 4 degrees C was limited to 9 days by overall visual quality (OVQ), while samples treated with NEW remained acceptable during the 14 days of the experiment. The shelf-life of controls stored at 7 degrees C was limited to 6 days by OVQ and browning, while that of samples treated with NEW were limited to 9 days by OVQ, browning and dryness. According to these results, a shelf-life extension of at least 5 days and 3 days in samples stored respectively at 4 degrees C and 7 degrees C can be achieved by treating shredded cabbage with NEW. NEW seems to be a promising method to prolong the shelf-life of MPV.     

Shelf-life extension of minimally processed carrots by gaseous chlorine dioxide

Chlorine dioxide (ClO(2)) gas is a strong oxidizing and sanitizing agent that has a broad and high biocidal effectiveness and big penetration ability; its efficacy to prolong the shelf-life of a minimally processed (MP) vegetable, grated carrots (Daucus carota L.), was tested in this study. Carrots were sorted, their ends removed, hand peeled, cut, washed, spin dried and separated in 2 portions, one to be treated with ClO(2) gas and the other to remain untreated for comparisons. MP carrots were decontaminated in a cabinet at 91% relative humidity and 28 degrees C for up to 6 min, including 30 s of ClO(2) injection to the cabinet, then stored under equilibrium modified atmosphere (4.5% O(2), 8.9% CO(2), 86.6% N(2)) at 7 degrees C for shelf-life studies. ClO(2) concentration in the cabinet rose to 1.33 mg/l after 30 s of treatment, and then fell to nil before 6 min. The shelf-life study included: O(2) and CO(2) headspace concentrations, microbiological quality (mesophilic aerobic bacteria, psychrotrophs, lactic acid bacteria, and yeasts), sensory quality (odour, flavour, texture, overall visual quality, and white blushing), and pH. ClO(2) did not affect respiration rate of MP carrots significantly (alpha< or =0.05), and lowered the pH significantly (alpha< or =0.05). The applied packaging configuration kept O(2) headspace concentrations in treated samples in equilibrium and prevented CO(2) accumulation. After ClO(2) treatment, the decontamination levels (log CFU/g) achieved were 1.88, 1.71, 2.60, and 0.66 for mesophilic aerobic bacteria, psychrotrophs, and yeasts respectively. The initial sensory quality of MP carrots was not impaired significantly (alpha< or =0.05). A lag phase of at least 2 days was observed for mesophilic aerobic bacteria, psychrotrophs, and lactic acid bacteria in treated samples, while mesophilic aerobic bacteria and psychrotrophs increased parallelly. Odour was the only important attribute in sensory deterioration, but it reached an unacceptable score when samples were already rejected from the microbiological point of view. The shelf-life extension was limited to one day due to the restricted effect of the ClO(2) treatment on yeast counts. Nevertheless, ClO(2) seems to be a promising alternative to prolong the shelf-life of grated carrots.     

Inactivation kinetics of inoculated Escherichia coli O157:H7 and Salmonella enterica on lettuce by chlorine dioxide gas

The purpose of this investigation was to study inactivation kinetics of inoculated Escherichia coli O157:H7 and Salmonella enterica on lettuce leaves by ClO(2) gas at different concentrations (0.5, 1.0, 1.5, 3.0, and 5.0 mg l(-1)) for 10 min and to determine the effect of ClO(2) gas on the quality and shelf life of lettuce during storage at 4 degrees C for 7 days. One hundred microliters of each targeted organism was separately spot-inoculated onto the surface (5 cm(2)) of lettuce (approximately 8-9 log CFU ml(-1)), air-dried, and treated with ClO(2) gas at 22 degrees C and 90-95% relative humidity for 10 min. Surviving bacterial populations on lettuce were determined using a membrane transferring method, which included a non-selective medium followed by a selective medium. The inactivation kinetics of E. coli O157:H7 and S. enterica was determined using first-order kinetics to establish D-values and z-values. The D-values of E. coli and S. enterica were 2.9+/-0.1 and 3.8+/-0.5 min, respectively, at 5.0 mg l(-1) ClO(2) gas. The z-values of E. coli and S. enterica were 16.2+/-2.4 and 21.4+/-0.5 mg l(-1), respectively. A 5 log CFU reduction (recommended by the United States Food and Drug Administration) for E. coli and S. enterica could be achieved with 5.0 mg l(-1) ClO(2) gas for 14.5 and 19.0 min, respectively. Treatment with ClO(2) gas significantly reduced inherent microflora on lettuce and microbial counts remained significantly (p<0.05) lower than the uninoculated control during storage at 4 degrees C for 7 days. However, treatment with ClO(2) gas had a significantly (p<0.05) negative impact on visual leaf quality. These results showed that treatment with ClO(2) gas significantly reduced selected pathogens and inherent microorganisms on lettuce; however, the processing conditions would likely need to be altered for consumer acceptance.     

Comparative Growth ofEscherichia coli0157:H7, Spoilage Organisms and Shelf-Life of Shredded Iceberg Lettuce Stored under Modified Atmospheres

The objective of this work was to compare organoleptic and microbiological spoilage with the survival of Escherichia coli 0157:H7 in modified atmosphere (MA) stored shredded lettuce. The rates of growth of E coli 0157:H7, increase in aerobic plate counts (APC g⁻¹), and rates of visual spoilage of shredded lettuce held under air or MA at 13 and 22°C were compared. Samples were inoculated with nalidixic acid-resistant E coli 0157:H7 (ATCC 35150) and placed in a chamber which was continuously flushed with gas mixtures of 0/10/90, 3/0/97, 5/30/65, 20/0/80 (O₂/CO₂/N₂, v/v) and held at 13 or 22°C. APC growth was inhibited in 5/30/65 (O₂/CO₂/N₂) at 13°C compared to all other atmospheres which were not significantly different from each other. The growth rates for both E coli 0157:H7 and APC were greatest in air at 22°C. Carbon dioxide concentration had no significant effect on the growth of E coli 0157:H7 at either temperature. The shelf-life of shredded lettuce, as judged by appearance, was extended in atmospheres containing 30% CO₂ by approximately 300% compared to air. The APC were similar at the time when the shredded lettuce samples were judged unacceptable regardless of shelf-life. However, the extended shelf-life provided by the MA allowed E coli 0157:H7 to grow to higher numbers compared to air-held shredded lettuce.     

Evaluation of gaseous chlorine dioxide as a sanitizer for killing Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, and yeasts and molds on fresh and fresh-cut produce

Gaseous chlorine dioxide (ClO2) was evaluated for effectiveness in killing Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes on fresh-cut lettuce, cabbage, and carrot and Salmonella, yeasts, and molds on apples, peaches. tomatoes, and onions. Inoculum (100 microl, ca. 6.8 log CFU) containing five serotypes of Salmonella enterica, five strains of E. coli O157:H7, or five strains of L. monocytogenes was deposited on the skin and cut surfaces of fresh-cut vegetables, dried for 30 min at 22 degrees C, held for 20 h at 4 degrees C, and then incubated for 30 min at 22 degrees C before treatment. The skin surfaces of apples, peaches, tomatoes, and onions were inoculated with 100 microl of a cell suspension (ca. 8.0 log CFU) containing five serotypes of Salmonella, and inoculated produce was allowed to dry for 20 to 22 h at 22 degrees C before treatment. Treatment with ClO2 at 4.1 mg/liter significantly (alpha = 0.05) reduced the population of foodborne pathogens on all produce. Reductions resulting from this treatment were 3.13 to 4.42 log CFU/g for fresh-cut cabbage, 5.15 to 5.88 log CFU/g for fresh-cut carrots, 1.53 to 1.58 log CFU/g for fresh-cut lettuce, 4.21 log CFU per apple, 4.33 log CFU per tomato, 1.94 log CFU per onion, and 3.23 log CFU per peach. The highest reductions in yeast and mold populations resulting from the same treatment were 1.68 log CFU per apple and 2.65 log CFU per peach. Populations of yeasts and molds on tomatoes and onions were not significantly reduced by treatment with 4.1 mg/liter ClO2. Substantial reductions in populations of pathogens on apples, tomatoes, and onions but not peaches or fresh-cut cabbage, carrot, and lettuce were achieved by treatment with gaseous ClO2 without markedly adverse effects on sensory qualities.     

Predictive modelling for packaging design: equilibrium modified atmosphere packages of fresh-cut vegetables subjected to a simulated distribution chain

The impact of temperature fluctuations in a simulated cold distribution chain, typical of commercial practice, was investigated on both the microbial and sensorial quality of equilibrium modified atmosphere (EMA) packaged minimally processed vegetables. The internal O2 concentration of the designed packages could be predicted for the different steps of the simulated distribution chain by applying an integrated mathematical system. The internal atmosphere in the packages remained in its aerobic range during storage in the chain due to the application of high permeable packaging films for O2 and CO2. Spoilage microorganisms were proliferating fast on minimally processed bell peppers and lettuce. Yeasts showed to be the shelf-life limiting group. Visual properties limited the sensorial shelf-life. Listeria monocytogenes was able to multiply on cucumber slices, survived on minimally processed lettuce and decreased in number on bell peppers due to the combination of low pH and refrigeration. Aeromonas caviae was multiplying on both cucumber slices and mixed lettuce, but was as well inhibited by the low pH of bell peppers. Storage temperature control was found to be of paramount importance for the microbial (spoilage and safety) and sensorial quality evaluation of EMA-packaged minimally processed vegetables.     

Color of Minimally Processed Potatoes as Affected by Modified Atmosphere Packaging and Antibrowning Agents

Minimal processing of potatoes was studied by using different treatments of cut potatoes in combination with modified atmosphere packaging. Different packaging materials and peeling methods were evaluated. An L-cysteine (0.5%) and citric acid (2%) mixture prevented browning of potatoes effectively. Active modification of the atmosphere inside the package was necessary to achieve extended shelf-life. Nitrogen flushing was more effective than other gas treatments with a highly permeable multilayered polyolefin packaging material. Hand peeling and lye peeling resulted in better quality, but abrasion peeling was undesirable for fresh potatoes. The shelf-life of the minimally processed products could be extended to nearly 3 wk under refrigerated storage.     

Efficacy of chlorine dioxide gas as a sanitizer of lettuce leaves

Aqueous solutions of sodium hypochlorite or hypochlorous acid are typically used to sanitize fresh fruits and vegetables. However, pathogenic organisms occasionally survive aqueous sanitization in sufficient numbers to cause disease outbreaks. Chlorine dioxide (ClO2) gas generated by a dry chemical sachet was tested against foodborne pathogens on lettuce leaves. Lettuce leaves were inoculated with cocktail of three strains each of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium and treated with CLO2 gas for 30 min, 1 h, and 3 h in a model gas cabinet at room temperature (22 +/- 2 degrees C). After treatment, surviving cells, including injured cells, were enumerated on appropriate selective agar or using the overlay agar method, respectively. Total ClO2, generated by the gas packs was 4.3, 6.7, and 8.7 mg after 30 min, 1 h, and 3 h of treatment, respectively. Inoculated lettuce leaves exposed to ClO2 gas for 30 min experienced a 3.4-log reduction in E. coli, a 4.3-log reduction in Salmonella Typhimurium, and a 5.0-log reduction in L. monocytogenes when compared with the control. After 1 h. the three pathogens were reduced in number of CFU by 4.4. 5.3, and 5.2 log, respectively. After 3 h, the reductions were 6.9, 5.4, and 5.4 log, respectively. A similar pattern emerged when injured cells were enumerated. The ClO2, gas sachet was effective at killing pathogens on lettuce without deteriorating visual quality. Therefore, this product can be used during storage and transport of lettuce to improve its microbial safety.     

Microbial and sensory quality of commercial fresh processed red lettuce throughout the production chain and shelf life

Red pigmented 'Lollo Rosso' lettuce was processed under usual and controlled conditions in an industrial plant. At different steps of the production chain (reception, shredding, washing, draining, rinsing, centrifugation, and packaging), microbial counts were evaluated. Following industrial practices, processed lettuce was packaged at 5 degrees C in sealed polypropylene (PP) bags with an initial atmosphere containing 3 kPa O(2) and 5 kPa CO(2). The numbers of psychrotrophic bacteria, coliform and lactic acid bacteria (LAB) were influenced by all the studied steps of the production chain of the fresh processed 'Lollo Rosso' lettuce. Shredding, rinsing and centrifugation in particular increased bacterial counts. During a storage period of 7 days at 5 degrees C, sensory attributes (general appearance, texture, aroma, translucency, initial and persistent off-odors, leaves superficial browning, leaves edges browning, and decay) as well as microbial counts (psychrotrophic and mesophilic bacteria, coliforms and lactic acid bacteria) were monitored. Due to high microbial counts and off-odors evaluation, a shelf life shorter than 7 days should be considered for fresh processed 'Lollo Rosso' lettuce.     

Effects of aqueous chlorine dioxide treatment on nutritional components and shelf-life of mulberry fruit (Morus alba L.)

Effects of aqueous chlorine dioxide (ClO(2)) treatment on nutritional components and shelf-life of mulberry fruit (Morus alba L.) were investigated. Mulberry fruit were immersed into 20, 60, and 80 mg/l ClO(2) solutions for 5, 10, and 15 min, respectively. Mulberries were then rinsed with potable tap water for 1 min and stored at -1°C for 14 d. ClO(2) treatment was effective in retention of flavonoid, ascorbic acid, reducing sugar, and titratable acid. ClO(2) concentration and treatment time were significant factors affecting ClO(2) treatment. The shelf-life of the samples treated by 60 mg/l ClO(2) for 15 min was extended to 14 d compared to 8 d for the control. No ClO(2), ClO(2)(-), or ClO(3)(-) residues were detected in samples treated by 60 mg/l ClO(2) for 15 min. These results indicated that ClO(2) treatment was a promising approach to preserve mulberry fruit with no significant risks of chemical residues.     

Allicin Inhibits Microbial Growth and Oxidative Browning of Fresh-Cut Lettuce (Lactuca sativa) During Refrigerated Storage

Fresh-cut lettuce has a short shelf life since it is very perishable and susceptible to enzymatic browning. The aim of this study was to examine the effectiveness of allicin treatment in prolonging the shelf life of fresh-cut lettuce (Lactuca sativa L. var. angustana Irish). Fresh-cut lettuce slices were treated with water (control), 0.2 and 1 % of allicin solutions, respectively, and stored at 4 °C, >90 % relative humidity. Sensory parameters, microbiological indicators, and physiological indices were determined at 0, 2, 4, and 6 days of storage. The sensory analyses revealed that allicin inhibited the color change and maintained the visual quality of lettuce slice without impairing flavor. Allicin treatment delayed microbial growth at cold storage, as evidenced by the lowered total viable counts (decreased by 2.52 log cfu/g) and yeast and mold counts (decreased by 1.59 log cfu/g) after 6 days in 1 % allicin-treated samples compared to control samples. In addition, differences between lettuce treated with 1 % allicin and control slices in objective color (total color change, chrome, and hue angle), total phenolic compounds and quinones content, activities of browning-related enzymes, and antioxidative enzymes suggested that allicin had antioxidative properties. Conclusively, it was demonstrated for the first time that allicin effectively protected fresh-cut lettuce from tissue browning and microbiological spoilage. These findings indicate that allicin has great potential as a natural additive to extend the shelf life of fresh-cut lettuce.     

臭氧协同气调包装对鲜切叶菜的保鲜作用研究

采用臭氧水处理鲜切大白菜,并进行气调包装贮藏,通过正交实验法分析相关生理指标与保鲜效果,主要研究了4℃贮藏期间菌落总数、失重率、细胞膜透性、多酚氧化酶活性、VC含量和感官品质的变化。实验结果显示:臭氧水处理结合气调包装能有效控制微生物数量,保护了细胞膜透性及降低了VC含量的损失,并对多酚氧化酶有抑制作用,感官品质优良,可使鲜切白菜在4℃条件下保藏至20d以上。极差分析表明:优化的工艺参数为1.44mg/L的臭氧水处理5min协同5%O2/20%CO2/75%N2的气调包装。     

气体二氧化氯对葡萄杀菌效果及品质的影响

以‘巨峰’葡萄为试材,从其表面分离优势菌并鉴定其为大肠杆菌与考克氏菌,利用NaClO₂与干冰间接反应开发一种气体二氧化氯(ClO₂)处理方法以灭活葡萄表面优势菌,通过测定菌落总数对数值减少量评估气体ClO₂对葡萄的杀菌效果,同时通过测定4℃贮藏30 d期间葡萄样品的色泽参数、果实硬度、质量损失率以及可溶性固形物含量评估气体ClO₂对葡萄品质的影响。结果表明,气体ClO₂处理对接种于葡萄表面的大肠杆菌与考克氏菌具有良好杀灭效果。当ClO₂累积浓度从131μL/(L·h)提升至599μL/(L·h),大肠杆菌菌落总数对数值减少量从1.6(lg(CFU/g))升至3.5(lg(CFU/g)),考克氏菌菌落总数对数值减少量从1.0(lg(CFU/g))升至4.5(lg(CFU/g))。与对照组(S0)相比,经ClO₂处理后贮藏30 d期间葡萄色泽并没有明显变化,与S0和低累积浓度处理组(S1)相比,高累积浓度处理组(S2)在4℃贮藏30 d后...     

Effectiveness of two-sided UV-C treatments in inhibiting natural microflora and extending the shelf-life of minimally processed 'Red Oak Leaf' lettuce

The use of UV-C radiation treatments to inhibit the microbial growth and extend the shelf-life of minimally processed 'Red Oak Leaf' lettuce was investigated. Initially, UV-C resistance of 20 bacterial strains from different genera often associated with fresh produce (Enterobacter, Erwinia, Escherichia, Leuconostoc, Pantoea, Pseudomonas, Rahnela, Salmonella, Serratia and Yersinia) were tested in vitro. Most of the bacterial strains were inhibited with the minimum dose (30 J m(-2)). Erwinia carotovora, Leuconostoc carnosum, Salmonella typhimurium, and Yersinia aldovae were the most resistant strains requiring a UV-C dose of 85 J m(-2) to completely inhibit growth. An in vivo study consisted of treating minimally processed 'Red Oak Leaf' lettuce (Lactuca sativa) with UV-C at three radiation doses (1.18, 2.37 and 7.11 kJ m(-2)) on each side of the leaves and storing the product under passive MAP conditions at 5 degrees C for up to 10 days. The gas composition inside packages varied significantly among the treatments, with CO2 concentrations positively and O2 concentrations negatively correlating with the radiation dose. All the radiation doses were effective in reducing the natural microflora of the product, although the highest doses showed the greatest microbial inhibitions. Taking into account the microbial limit set by Spanish legislation [Boletín Oficial del Estado (BOE), 2001. Normas de higiene para la elaboración, distribución y comercio de comidas preparadas, Madrid, Spain, Real Decreto 3484/2000, pp. 1435-1441], all UV-C treatments extended the shelf-life of the product. However, the 7.11 kJ m(-2) dose induced tissue softening and browning after 7 days of storage at 5 degrees C. Therefore, the use of two sided UV-C radiation, at the proper dose, is effective in reducing the natural microflora and extending the shelf-life of minimally processed 'Red Oak Leaf' lettuce.     

UV-C radiation as a novel technique for keeping quality of fresh processed ‘Lollo Rosso’ lettuce

Fresh processed ‘Lollo Rosso’ lettuce (Lactuca sativa) was exposed to different doses (0.4, 0.81, 2.44, 4.07, and 8.14 kJ/m²) of ultraviolet-C (254 nm, UV-C) radiation, and stored up to 9 and 10 days at 5 °C. While minimal processing did not induce significant increases in respiration rate, UV-C radiation did. Consequently, gas composition within bags containing radiated and control lettuce pieces changed according with the increase in respiration rate. All UV-C radiation doses decreased growth of psychrotrophic bacteria, coliform, and yeast, but only significant differences were found when the highest level was applied. UV-C radiation seemed to stimulate the growth of lactic acid bacteria, probably due to reduced growth of competitive flora. After 7 days of storage the highest dose resulted in increased tissue brightness, and browning was reduced when 2.44, 4.07, and 8.14 kJ/m² were applied. UV-C radiation at an appropriate dose could reduce microbial loads without adversely affecting sensorial quality of ‘Lollo Rosso’ lettuce.     

Effect of Modified Atmosphere Packaging and Soluble Gas Stabilization on the Shelf Life of Skinless Chicken Breast Fillets

The suitability of soluble gas stabilization (SGS) to dissolve CO₂ into skinless chicken breast fillets before modified atmosphere (MA) packaging (MAP) was investigated. Head space gas composition (%), top web deflation (mm), muscle surface color (Minolta L*a*b*), pH, exudates in the packages (%), microbial characteristics, and off‐odor were assessed in the packaged fillets. Increased SGS treatment time (2 versus 12 h) before MA packaging increased the CO₂ content in the packaged fillets and counteracted package collapse. High package filling degree (51.8%) (low gas to product volume ratio) gave significantly (P < 0.001) lower CO₂ content in head space than normal filling degree (29.7%). Color, pH, and package exudates were not affected by SGS treatment. Aerobic plate count (APC), Enterbacteriaceae count (EC), and lactic acid bacteria (LAB) increased significantly (P < 0.001) at each sampling during storage (5, 11, 17, and 24 d). SGS treatment significantly (P < 0.015) decreased APC, EC, and Pseudomonas spp. counts (PC) compared with no SGS treatment. Filling degree did not have a significant effect on the investigated microbiological characteristics. Off‐odor scores correlated highest with EC (r²_(adj)= 0.82). Fillets SGS treated in 12 h were the only one not rejected at off‐odor evaluation on day 24. The samples stored in air spoiled after 5 d. SGS treatment in combination with MAP can be used successfully on chicken breast fillets to improve the microbiological (APC, EC, and PC) and sensorial characteristics, and in addition reduce package collapse and possibly increase the filling degree.     

Microbial shelf-life of high-pressure-homogenised milk

The anti-bacterial effect of high pressure homogenisation (HPH) on milk is widely reported but the shelf-life of HPH-treated milk, as reported in this communication has not been studied thus far. Raw whole milk was homogenised at 200 or 250 MPa at 55 or 70 °C and counts of total bacteria (TBC), psychrotrophs, pseudomonads, coliforms, lactobacilli, Bacillus cereus and Staphylococcus aureus were determined throughout subsequent storage for 14 days at 4 °C. Immediately after HPH treatment, counts of all bacteria were below the level of detection but after storage for 14 days at 4 °C, TBC, psychrotroph and pseudomonad counts had reached ∼10⁸ cfu mL⁻¹ in all samples treated with HPH. The limited shelf-life obtained indicates that HPH of milk at these processing parameters it is not a suitable alternative to pasteurisation for extending the shelf-life of milk.     

Effect of ozonated water treatment on microbial control and on browning of iceberg lettuce (Lactuca sativa L.)

We examined the effect of ozonated water treatment on microbial control and quality of cut iceberg lettuce (Lactuca sativa L.). Fresh-cut lettuce was washed in ozonated water (3, 5, and 10 ppm) for 5 min at ambient temperature. The native bacterial population on the lettuce declined in response to a rise in ozone concentration. However, there was no further bacterial reduction (1.4 log CFU/g) above 5 ppm ozone. Although ozonated water treatment increased the phenylalanine ammonia lyase (PAL) activity of the lettuce stored at 10 degrees C compared with the water wash treatment after 1 day of storage, the concentration of ozone did not affect PAL activity. The a* value of the residue of the lettuce methanol extracts, which reflects the extent of browning, increased dramatically in lettuce treated with 10 ppm ozonated water compared with other treatments. Treatment with 3 or 5 ppm ozonated water resulted in more rapid changes in the a* value than after the water treatment. The combined treatment of hot water (50 degrees C, 2.5 min) followed by ozonated water (5 ppm, 2.5 min) had the same bactericidal effect as treatment with ozonated water (5 ppm, 5 min) or sodium hypochlorite (NaOCl, 200 ppm, 5 min), giving a reduction in bacteria numbers of 1.2 to 1.4 log CFU/g. The ascorbic acid content of the lettuce was not affected by these treatments. The combined treatment of hot water followed by ozonated water greatly inhibited PAL activity for up to 3 days of storage at 10 degrees C. Treatment with this combination greatly suppressed increases in the a* value, thus retarding the progress of browning compared with other treatments throughout the 6-day storage. NaOCl treatment also inhibited browning for up to 3 days of storage. Bacterial populations on the lettuce treated with sanitizers were initially reduced but then showed rapid growth compared with that of the water wash treatment, which did not reduce bacterial counts initially.     

ESTIMATE OF THE SHELF-LIFE OF BEEF UNDER VACUUM PACKAGING BY OBJECTIVE AND SUBJECTIVE MEASUREMENTS

Abstract This work was carried out in order to establish variables which would be useful to estimate the shelf-life of vacuum packaged beef from the Pirenaica breed. This breed is the main source of beef meat in the Spanish West Pyrenees. Two different fresh beef cuts (rib and chuck) samples were evaluated for total fatty acid composition, pH, lipid oxidation (TBA values), total bacterial counts (APC), Enterobacteriaceae counts and by sensory evaluation after 15 and 30 day under vacuum and then after 3 days of display. The variables that contributed to separating the storage periods determining the shelf-life of vacuum packaged beef were TBA, APC, Enterobacteriaceae counts and the sensory variables of color, odor and overall appearance.     

Evaluation of chlorine dioxide gas residues on selected food produce

In recent years, the consumption of fresh fruits and vegetables has greatly increased, and so has its association with contamination of several foodborne pathogens (Listeria, Salmonella, and Escherichia coli). Hence, there is a need to investigate effective sanitizer systems for produce decontamination. Chlorine dioxide (ClO(2)), a strong oxidizing gas with broad spectrum and sanitizing properties, has previously been studied for use on selected fruits and vegetables. ClO(2) gas treatments show great potential for surface pathogen reduction; however its use from a residue safety standpoint has yet to be assessed. Thus, the objective of this study was to evaluate residues of ClO(2), chlorite, chlorate, and chloride on selected fresh produce surfaces after treatment with ClO(2) gas. A rinse procedure was used and water samples were analyzed by N, N-diethyl-p-phenylenediamine and ion chromatography method (300.0). Seven different foods--tomatoes, oranges, apples, strawberries, lettuce, alfalfa sprouts, and cantaloupe--were analyzed after ClO(2) treatment for surface residues. Very low residues were detectable for all the food products except lettuce and alfalfa sprouts, where the measured concentrations were significantly higher. Chlorine dioxide technology leaves minimal to no detectable chemical residues in several food products, thus result in no significant risks to consumers. Practical Application: Potential for chlorine dioxide gas treatments as an effective pathogen inactivation technology to produce with minimal risk for consumers.