Innovative processes and technologies for modified atmosphere packaging of fresh and fresh-cut fruits and vegetables

Modified atmosphere packaging (MAP) technology has been commercially viable since the 1970s. Currently, MAP is extensively used worldwide to preserve the quality and extend the shelf-life of whole fresh fruits and vegetables, but is also increasingly used to extend the shelf-life of minimally processed fresh fruit and vegetables. This review discusses new processes and technologies that can be used to improve quality preservation and consumer acceptability of minimally processed produce where high respiration rates and challenging degradation processes operate. New packaging innovations are enabling producers and retailers to further maintain quality for longer. Innovative approaches to extend shelf-life include active MAP with differentially permeable films, films that incorporate antimicrobial properties, edible coatings that confer barriers properties, and the use of non-traditional gases to modify respiration. Intelligent packaging using integrated sensor technologies that can indicate maturity, ripeness, respiration rate and spoilage are also appearing. This review demonstrates that preservation technologies and associated packaging developments that can be combined with modified atmosphere are constantly evolving technology platforms. Adoption of combinations of technology improvements will be critical in responding to commercial trends towards more minimally processed fresh-cut and ready-to-eat fruit and vegetable products, which require specialized packaging solutions.     

A rapid multi-residue method for the determination of pesticide residues in choi sum, yardlong beans and aubergines

A rapid multi-residue modified QuEChERS method has been developed to analyse 20 pesticide residues in choi sum, yardlong beans and aubergines by gas chromatography with flame photometric and electron capture detectors. Primary secondary amine in dispersive form was omitted in the extraction step but instead packed in a Pasteur glass pipette for column cleanup. The recoveries for all 20 pesticides except chlorothalonil at 10-500 μg kg⁻¹ fortification levels ranged from 74.0% to 117%. Similar recoveries of 81.7-117% were obtained for all organochlorine and pyrethroid pesticides including chlorothalonil using silica gel cleanup. The relative standard deviation obtained was below 14.9%. The limit of quantification was in the range 1-10 μg kg⁻¹. The method has high selectivity for pesticides in vegetables containing high amount of chlorophyll, pigment and coloured compounds such as in choi sum and aubergines. The method was used to analyse 132 vegetable samples from residue survey.     

Determination of nitrates by a novel ion chromatographic method: occurrence in leafy vegetables (organic and conventional) and exposure assessment for Italian consumers

A novel ion chromatographic method to detect nitrates in vegetables was developed, and the nitrate contents in green salad (a mixture of endive and prickly lettuce), lettuce, chicory, rocket and spinach were determined from Italian markets in 1996 -2002. These leaf vegetables were included because they are currently supposed to provide most of the nitrate intake in the typical Italian diet. The highest content of nitrate was detected in chicory (6250 mg kg -1 ) and rocket (6120 mg kg -1 ), which are consumed in large quantities in some regions of Italy. Green salad and lettuce contained less nitrate (highest values = 4200 and 3300 mg kg -1 , respectively), but because they are consumed more generally, they provided 60% of the total intake of nitrates. Only a few samples were above the legal limits, with seasonal variation. A significantly higher nitrate content was found in organically grown green salad and rocket than in those conventionally produced. These data indicate that the average intake of nitrates from leafy vegetables is below the acceptable daily intake, i.e. 3.7 mg nitrate ion kg -1 body weight day -1 , but the total intake should be monitored to protect groups at risk, such as children and vegetarians.     

Optimization for Preservation of Selenium in Sweet Pepper Under Low-Vacuum Dehydration

Response Surface Methodology (RSM) was used for optimizing the drying technology of sweet pepper under low-vacuum. It was found that pH value has greater influence on the organic Se index, while drying temperature has greater effect on the chlorophyll index. The optimized parameters of drying temperature, pH value and blanching time were obtained, respectively.     

Second order derivative spectrophotometric method for determination of vitamin C content in fruits,vegetables and fruit juices

A second-order derivative UV spectrophotometric method for determination of vitamin C [ascorbic acid (AA)] content in a variety of natural samples is described. The method is based on the measurement of a peak–baseline amplitude in the second derivative of the AA spectrum at 267.5 nm. The following corresponding regression equation was obtained within the concentration range 2×10^-5 to 1×10^-4 M AA (3.5–17.6 g/cm³ AA) in 1.0 M HCl solution: ²D_267.5=2.420×10⁴ c+0.025; the correlation coefficient was 0.9993 and the detection limit 4.2×10^-6 M. The results obtained by analysing 21 different species of fruits, vegetables and juices indicated a possibility for a more extensive application of the proposed method. This method is rapid, simple and requires no pretreatment of the analysed material, which makes it suitable for routine analyses. The reliability of the method was confirmed by comparative determinations with the generally accepted 2,6-dichloroindophenol method.     

Determination of atrazine and carbaryl pesticide residues in vegetable samples using a multianalyte dipstick immunoassay format

A dipstick assay for the simultaneous determination of atrazine and carbaryl in vegetable samples was developed. The analytical method involved a fast extraction procedure followed by a multi-strip membrane test. The assay took 10 min, with a detection limit (naked eye) of 10 and 200 µg l^-1 for atrazine and carbaryl, respectively. The cross-reactivities to related compounds tested were negligible except for propazine. Quantification of the pesticides was carried out by measuring the dot colour with a spectrophotometer. IC₅₀ values (inhibition constant at 50% of the maximum binding) of 2.04 μg l^-1 for atrazine and 92.8 μg l^-1 for carbaryl were achieved by this approach. Vegetable samples were extracted with MeOH. The proposed methodology was used to analyse atrazine and carbaryl and check for compliance with European Union maximum residue levels for vegetables. Recoveries (75-105%) were in agreement with those obtained by GC/MS or HPLC. Standard curves using 25% methanol/75% TBS were used for food sample assays using a multi-analyte dipstick. IC₅₀ values were 9.2 μg l^-1 for atrazine and 179.2 μg l^-1 for cabaryl.     

北京市蔬菜、水果中有机磷农药残留现状调查

为了解北京市蔬菜、水果中有机磷农药残留情况，2002年在北京市抽检样品354件进行13种有机磷监测，其中蔬菜28l件，水果73件。检测结果显示7．6％的检品不符合国家标准。叶菜类(14，占9．3％)和根茎类(8，占17．4％)蔬菜的不合格率明显高于瓜菜、果菜类(2，占2．4％)蔬菜和水果(3，占4．1％)。13种有机磷检测出12种，其中禁用农药占53％。本市种植的蔬菜、水果与外埠进京产品的有机磷农药残留情况无显差别，超市、集贸市场、批发市场销售的产品的不合格率亦无显差别。     

Effects of a family-based sensory education on vegetable and fruit variety in children

Several experimental studies implemented in schools have shown that sensory education reduces children’s neophobia and increases their sensory discrimination abilities. However, it is not known whether sensory education has an effect on children’s consumption, particularly on the variety of fruits and vegetables consumed, and whether it is effective when implemented in families.The effect on fruit and vegetable intake of a five months family-based sensory programme was examined in children aged 7–11 (with 32 children in the intervention group and 19 in the control group). The children's parents completed four 24-hour recalls at the beginning and after the intervention to assess their children’s fruit and vegetable intake. Variety indexes were calculated on the basis of the number of different fruits or vegetables consumed during the four 24-hour recalls.The results showed that the vegetable variety decreased in the control group, while it remained stable in the intervention group. No effects of the programme were observed for the fruit variety.The sensory education programme implemented in families prevented the variety of vegetables from decreasing over time. The results of this preliminary study and its long-term effects need to be confirmed by further investigations, with a different methodology than the 24-hour recall.     

Evaluation of Zataria multiflora Boiss. essential oil activity against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes by propidium monoazide quantitative PCR in vegetables

Essential oils (EOs) have long been applied as flavoring agents in foods, and due to their content in antimicrobial compounds, they have potential as natural agents for food preservation. Recently, real-time PCR in combination with PMA has successfully been applied to discriminate between live Escherichia coli O157:H7 and dead bacteria killed by cumin, clove, oregano and cinnamon EOs. In this study, initial experiments were performed in order to elucidate the minimum bactericidal concentration of Zataria multiflora EOs on E. coli O157:H7, Salmonella enterica and Listeria monocytogenes. Thereafter PMA-qPCR was applied in order to selectively quantify life cells within a bacterial population treated with Z. multiflora EO. Inactivation was obtained at EO concentrations of 0.02, 0.035, 0.045 for L. monocytogenes, E. coli O157:H7 and S. enterica, respectively. L. monocytogenes were totally killed in 30 min while it took 1 h 30 min for the gram negative pathogens. As a conclusion Z. multiflora EO has potential as natural food additive or biopreservative since it was able to irreversibly inactivate the three pathogens tested, at lower concentrations than other EOs and short exposition times. In addition, the PMA-qPCR approach proved efficient to selectively detect live pathogenic bacteria in vegetables following inactivation with Z. multiflora EO.     

Consumption of raw vegetables and fruits: a risk factor for Campylobacter infections

The purpose of this study was to determine the prevalence of Campylobacter in fresh vegetables and fruits at retail level in the Netherlands, and to estimate its implications on the importance of vegetables and fruits as risk factor for campylobacteriosis.Thirteen of the 5640 vegetable and fruit samples were Campylobacter positive, resulting in a prevalence of 0.23% (95% confidence interval (Cl): 0.12-0.39%). The prevalence of packaged products (0.36%, 95% Cl: 0.17-0.66) was significantly higher than of unpackaged products (0.07; 95% Cl: 0.01-0.27). No statistical differences were found between seasons.Combining the mean prevalence found in this study with data on the consumption of vegetables and fruits, an exposure of 0.0048 campylobacters ingested per person per day in the Netherlands by transmission via vegetables and fruits, was calculated. This exposure, as input in a Beta-Poisson dose-response model, resulted in an estimated number of 5.3 × 10⁵ cases of infection with Campylobacter per year for the whole Dutch population. This constitutes the consumption of raw vegetables and fruits, especially when packaged, to be a risk factor for Campylobacter infections.