Chemical characterization and functional properties of selected leafy vegetables for innovative mixed salads

The content of bioactive compounds and antioxidant capacity of nine vegetables of conventional and unconventional utilization in salad mixtures were studied. The total phenolic and flavonoid contents ranged between 39.6–148.5 mg GAE/100g FW and 76.3–217.4 mg QE/100g FW, respectively. Ascorbic acid content ranged between 16.4 and 198.8 mg AAE/100g FW. Antioxidant capacity was assessed using DPPH, FRAP, and ORAC methods; values were in the range of 48.9–245.8 mg TE/100g FW, 67.7–335.8 mg TE/100g FW, and 104.86–833.9 mg TE/100g FW, respectively. Red cabbage, beet greens, parsley, and rocket exhibited the highest antioxidant capacities. Catechin was the most abundant phenolic compound identified in the free fraction, and p‐coumaric acid, quercetin, and caffeic acid in the hydrolyzed fraction. Results suggested that the presence of these phenolics could be of great importance in preventing some chronic and degenerative diseases when regularly consumed. Nonconventional vegetables showed high antioxidant properties, therefore, it is important to promote their consumption.

Practical applications

Not all vegetables have the same phenolic composition, and not all phenolics have the same antioxidant capacity. Knowledge of the bioactive content and antioxidant capacity profile in each vegetable could be of interest to consumers and the food industry for selecting the more suitable leaves to make salad mixtures with high nutritional and functional values. These compounds can prevent some chronic‐degenerative diseases related to oxidative stress, so it is important introduce them regularly into the diet. Moreover, the evaluation of nontraditional vegetables is intended to bring consumers toward a new source of bioactive compounds, prompting their consumption, and providing added value to certain plant parts that are sometimes considered as waste products.     

Quantitative risk assessment of listeriosis due to consumption of raw milk

The objectives of this study were to estimate the risk of illness for raw milk consumers due to Listeria monocytogenes in raw milk sold by permitted dealers, and the risk for people on farms who consume raw milk. Three scenarios were evaluated for raw milk sold by dealers: raw milk purchased directly from bulk tanks, from on-farm stores, and from retail. To assess the effect of mandatory testing of raw milk by regulatory agencies, the number of listeriosis cases per year was compared where no raw milk testing was done, only a screening test to issue a permit was conducted, and routine testing was conducted and milk was recalled if it was L. monocytogenes positive. The median number of listeriosis cases associated with consumption of raw milk from bulk tanks, farm stores, and retail for an intermediate-age population was 6.6 × 10(-7), 3.8 × 10(-5), and 5.1 × 10(-5) cases per year, respective ly. In populations with high susceptibility, the estimated median number of cases per year was 2.7 × 10(-7) (perinatal, i.e., pregnant women and their fetuses or newborns) and 1.4 × 10(-6) (elderly) for milk purchased from bulk tanks, 1.5 × 10(-5 ) (perinatal) and 7.8 × 10(-5) (elderly) for milk from farm stores, and 2.1 × 10(-5) (perinatal) and 1.0 × 10(-4) (elderly) for milk from retail. For raw milk consumed on farms, the median number of listeriosis cases was 1.4 × 10(-7) cases per year. A greater risk of listeriosis was associated with consumption of raw milk obtained from retail and farm stores as compared with milk obtained from bulk tanks. This was likely due to additional time-temperature combination steps in the retail and farm store models, which increased the chances for growth of L. monocytogenes in raw milk. A close relationship between prevalence of L. monocytogenes in raw milk and the values of disease incidence was observed. Hence, a reduction in the number of cases per year in all populations was observed when a raw milk-testing program was in place, especially when routine testing and recalling of milk was conducted.     

Influence of oxygen concentration and temperature on respiratory characteristics of fresh-cut green onion

The characteristics of the respiration rates in precut green onion, as influenced by oxygen levels and temperature, were examined to provide design factors for modified atmosphere packaging (MAP). Fresh-cut green onions ( Allium fistulosum L.) were prepared and sealed, with and without a CO₂ absorbent, in gas-tight glass containers that had initially been purged with air or a gas mixture (O₂ 9%/N₂ balance). The containers were stored at different temperatures (0, 10, 20 °C). At 10 °C, the maximum O₂ uptake rate (V_m) and the O₂ concentration at half-maximum (K_m) uptake rate were 30.95 mL kg⁻¹ h⁻¹ and 1.63%, respectively. Regardless of temperature, the lower O₂ limit was estimated to be about 1.0% O₂ on the basis of respiratory quotient (RQ) increase. Respiration of cut green onion was dependent on O₂ concentration as well as temperature, as shown by applying the Michaelis–Menten type model and the Arrhenius equation. However, the presence of CO₂ had little effect on O₂ uptake of cut green onion at relatively high O₂ concentrations (≤20%).     

Egg consumption patterns and Salmonella risk in Finland

To estimate the consumer risk of contracting Salmonella infection via shell eggs and to evaluate the effect of possible preventative measures, quantitative microbiological risk assessment is being developed in Finland. As a part of the risk assessment, a survey of 918 respondents was conducted to study how households purchase, store, handle, and use eggs. In addition, suitability of the Internet as a survey method was compared with a postal survey. Shell eggs were usually purchased once every 2 weeks (41% of all the respondents). Ninety-one percent of the respondents bought eggs in groceries and 93% stored eggs at chilled temperatures. The majority of the respondents (80%) only had eggs in their home for which the best-before date had not expired. Only 34% of the respondents said that they always washed their hands after breaking eggs. Consumption of well-cooked eggs accounted for 84%, consumption of soft-boiled eggs for 12%, and consumption of raw eggs for 4% of the total amount of eggs consumed. The elderly used eggs more frequently than the whole population, but the consumption of raw egg dishes decreased with age. The Internet survey was a rapid method for transmitting information, but its response rate was low (9%), and it did not appear to be a suitable tool for data collection in a general population. The results indicate that although the majority of the respondents had safe egg-handling practices, a substantial minority of the consumers had risk-prone behavior.     

Quantitative assessment of the microbial risk of leafy greens from farm to consumption: preliminary framework, data, and risk estimates

This project was undertaken to relate what is known about the behavior of Escherichia coli O157:H7 under laboratory conditions and integrate this information to what is known regarding the 2006 E. coli O157:H7 spinach outbreak in the context of a quantitative microbial risk assessment. The risk model explicitly assumes that all contamination arises from exposure in the field. Extracted data, models, and user inputs were entered into an Excel spreadsheet, and the modeling software @RISK was used to perform Monte Carlo simulations. The model predicts that cut leafy greens that are temperature abused will support the growth of E. coli O157:H7, and populations of the organism may increase by as much a 1 log CFU/day under optimal temperature conditions. When the risk model used a starting level of -1 log CFU/g, with 0.1% of incoming servings contaminated, the predicted numbers of cells per serving were within the range of best available estimates of pathogen levels during the outbreak. The model predicts that levels in the field of -1 log CFU/g and 0.1% prevalence could have resulted in an outbreak approximately the size of the 2006 E. coli O157:H7 outbreak. This quantitative microbial risk assessment model represents a preliminary framework that identifies available data and provides initial risk estimates for pathogenic E. coli in leafy greens. Data gaps include retail storage times, correlations between storage time and temperature, determining the importance of E. coli O157:H7 in leafy greens lag time models, and validation of the importance of cross-contamination during the washing process.     

钙处理浓度和温度对鲜切绿熟木瓜质量的影响

新鲜绿熟木瓜经清洗、消毒、去皮后刨成丝,分别用25℃的蒸馏水、0.5%(w/v)和1.0%(w/v)氯化钙溶液以及5℃的0.5%(w/v)氯化钙溶液处理,在5℃的冷库中贮藏12d,每隔2d检测鲜木瓜丝的硬度、L值、失重率和包装内二氧化碳含量。结果表明,鲜木瓜丝经钙处理可显著降低呼吸强度提高硬度,抑制褐变,减少失重,其中又以0.5%氯化钙处理为最好;5℃氯化钙溶液处理的鲜木瓜丝质量好于25℃氯化钙溶液处理的鲜木瓜丝。     

鲜切小白菜和生菜不同贮藏温度下货架期预测模型的建立

为研究鲜切小白菜和鲜切生菜在贮藏期间的品质变化,并预测其货架期,本文以鲜切小白菜和鲜切生菜为研究对象,对其贮藏期间的感官品质、细菌总数和大肠菌群数变化进行研究,并以细菌总数为自变量对低温与室温下鲜切小白菜和生菜货架期预测模型进行拟合。结果显示,在4℃与25℃下贮藏时间分别为10 d与3 d时,两种蔬菜的感官评价均大于5分,超过了消费者接受范围,细菌总数和大肠菌群数也在该贮藏时间时超出了标准规定范围,得出鲜切小白菜和鲜切生菜在4℃与25℃下的货架期终点分别为10 d与3 d;低温与室温下鲜切小白菜和鲜切生菜货架期预测模型拟合结果分别为:SL_4℃=ln{ln[5.096/（N₁-1.990）]}-1/0.279+7.452和SL_25℃=ln{ln[3.621/（N₁-3.651）]}-1/1.124+1.512;两个预测模型的偏差因子分别为0.979和1.001,准确因子分别为1.050和1.040,表明所建立的模型是有效的。      

Epidemiology and risk management of listeriosis in India

Listeria monocytogenes is a foodborne pathogen that can cause serious invasive illness, mainly in certain well-defined high-risk groups, including elderly and immunocompromised patients, pregnant women, newborns and infants. In India, this pathogen has been isolated from humans, animals and foods. The incidence of Listeria is generally comparable to those reported elsewhere in the world. In humans, maternal/neonatal listeriosis is the most common clinical form reported. Among animal populations, spontaneous abortions, subclinical mastitis, meningoencephalitis and endometritis were the commonest forms reported. The disease largely remains undiagnosed and under reported. From reported analyses of a variety of foods for Listeria, milk and milk products, meat and meat products, seafood and vegetables have been reported to be contaminated in India. The legal framework for microbiological safety of foods against microbes including L. monocytogenes is summarised. The epidemiological studies would help in understanding of the sources of infection and persistence and their risk assessment, routes of transmission, clinical forms and allow for better management of the infection.     

Analysis of nutrient and antinutrient content of underutilized green leafy vegetables

Analysis of chemical composition of 13 locally available underutilized green leafy vegetables (GLV) was the objective of this study. Moisture, ash and ether extract of the greens were in the range of 73–95 g/100 g, 0.77–3.54 g/100 g and 0.2–0.9 g/100 g, respectively. Four GLV had high iron content (13.15–17.72 mg/100 g) while the rest had lower levels (2.62–9.86 mg/100 g). Calcium content varied largely between the greens ranging from 41 mg/100 g in Polygala erioptera to 506 mg/100 g in Digera arvensis, whereas phosphorous ranged from 16 to 63 mg/100 g. Ascorbic acid was higher in Delonix elata (295 mg/100 g) and Polygala erioptera (85 mg/100 g) and lower in others (3–46 mg/100 g). Thiamine was found to be less than 0.1 mg/100 g in six greens and 0.1–0.33 mg/100 g in others. Total carotene content ranged between 10 and 35 mg/100 g in all with exceptionally high amount in Cocculus hirsutus (67 mg/100 g) and Delonix elata (60 mg/100 g). $\beta$-carotene was 13–25% of total carotene in all greens. Oxalate content was below 100 mg/100 g in five greens and less than 1400 mg/100 g in the remaining GLV. Tannin content ranged between 61 and 205 mg/100 g in all GLV with the exception of Coleus aromaticus (15 mg/100 g) and Delonix elata (1330 mg/100 g).     

Status and scope of kitchen gardening of green leafy vegetables in rural Tanzania: implications for nutrition interventions

Kitchen gardens in Tanzania are currently facing a variety of threats. However, many households depend on basic farming activities to meet household food needs. The objective of this study was to describe the current status and scope of kitchen gardening for improving the food security situation in the Morogoro and Dodoma regions of Tanzania. A cluster sampling method was used to select 383 households. The main respondents were mothers or caregivers responsible for food preparation. Techniques for data collection were observations, focus group discussions and face to face interviews. A small proportion (2.6%) of residents in the semi-arid Dodoma region had a kitchen garden as compared to the sub-humid Morogoro region (9.9%). Sweet potato leaves, cassava leaves, pumpkin leaves, cowpea leaves and African egg plant were the principal vegetables grown in the two areas. The market provided vegetables to 87% of the surveyed households. Vegetables sold at the market were mostly in the dried form, fresh vegetables in the market being those cultivated near ponds, especially during dry seasons. About 90% and 55% of the kitchen garden produce was used for home consumption in Dodoma and Morogoro, respectively. Women contributed 80% and 75%of the total labor for managing kitchen gardens in Dodoma and Morogoro, respectively. Socio-cultural factors (food habit and demand and supply of food materials), environmental factors (climatic factors, water availability), types of soils and farmers’ local knowledge and understanding (traditional knowledge and practices, formal and non-formal education) were the key determinants of vegetables grown in the traditional kitchen garden. Kitchen gardening was practised by few of the surveyed households and the diversity of the planted vegetables was low. Factors that influenced the presence of a kitchen gardens at household level were: sex of the household head (p?=?0.002), literacy status of the mother/caregiver (p?=?0.001) and the education level (p?=?0.001) of the respondent.     

Fortification of vegetarian diets for increasing bioavailable iron density using green leafy vegetables

There is a high prevalence of iron deficiency anaemia in many developing countries today; especially in vegetarian women. The major cause of this state is low bioavailability of nonheme iron from vegetarian diets. An investigation was undertaken to improve bioavailable contents of nonheme iron from vegetarian meals. Forty-eight meals with combinations of roti (unleavened whole cereal pancake) of one of the six cereals and one of the four commonly consumed green leafy vegetables (GLV) along with 35 meals with cereal roti and fruit vegetable/legume were tested for their in vitro dialysability of iron using simulated gastrointestinal conditions and standardised protocol with ⁵⁹Fe as a tracer. Average bioavailable iron density of GLV-based meals was significantly higher (1.2±0.7 mg /1000 kcal) as against the value in prevailing dietary patterns having cereal-legume or cereal-fruit vegetable combinations (0.36±0.17 mg/1000 kcal, p⩽0.001). Around 31 GLV-based meals were identified as having higher amounts of bioavailable iron density than 0.75 mg/1000 kcal. Thus, one such GLV-based meal per day will increase gross as well as bioavailable iron intake which will help in meeting daily requirements of iron especially for vegetarian women of reproductive age.     

Survival and distribution of Escherichia coli on diverse fresh-cut baby leafy greens under preharvest through postharvest conditions

Escherichia coli O157:H7 has been associated in multiple outbreaks linked to the consumption of whole produce and fresh-cut leafy vegetables. However, plant-based foods had not been traditionally recognized as a host for enteric pathogens until the elevated incidence of produce-related outbreaks became apparent. The survival dynamics of two cocktails of generic E. coli (environmental water, plant and soil isolates) and E. coli O157:H7 within the phyllosphere of Mizuna, Red Chard and Tatsoi during their production, harvest, minimal processing, packaging and storage over two greenhouse production cycles were studied. Genotyping of applied generic E. coli strains to evaluate their comparative survival and relative abundance in the phyllosphere by REP-PCR is also reported. The Mizuna, Red Chard and Tatsoi shoots were grown under standard greenhouse conditions and fertility management. Both E. coli cocktails were spray-inoculated separately and determined to result in an initial mean population density of log 4.2 CFU/cm². Leaves were harvested as mini-greens approximating commercial maturity, minimally processed in a model washing system treated with 3 mg/L of ClO₂ and stored for 7 days at 5 °C. Rapid decline of generic E. coli and E. coli O157:H7 populations was observed for all plant types regardless of the leaf age at the time of inoculation and the irrigation type across both seasonal growth cycle trials. The decline rate of the surviving populations for the fall season was slower than for the summer season. The minimal processing with 3 mg/L of ClO₂ was not sufficient to fully disinfect the inoculated leaves prior to packaging and refrigerated storage. Viable populations of E. coli and E. coli O157:H7 were confirmed throughout storage, including the final time point at the end of acceptable visual leaf quality. In this study, the ability of low populations of E. coli to survive during production and postharvest operations in selected mini-greens has been demonstrated. However, further field-based trials are needed to expand understanding of the post-contamination fate of enteric bacterial pathogens on leafy vegetables. In summary, this research work provides baseline data upon which to develop food safety preventive control guidance during the production and minimal processing of these crops.     

鲜切青椒优势腐败菌的分离纯化及鉴定

目的:筛选鲜切青椒中的优势腐败菌,揭示其腐败能力,并进行初步鉴定.方法:以北京地区“京甜3号”、“中椒7号”、“冠军椒王”、“强舟”四个青椒品种为实验材料,经过鲜切工艺处理后贮藏至腐败,采用平板计数法和划线分离法,从腐烂组织中筛选优势菌株,经过反接验证测定其腐败能力,并对优势腐败菌进行形态学和API20E、API50CH生理生化鉴定结果:四个品种的鲜切青椒中均筛选出优势菌株A、B;菌株B对鲜切青椒具有致腐性,而菌株A不具有腐败能力;经过显微镜观察及革兰氏染色后鉴定B为革兰氏阴性杆菌,API20E、API50CH初步鉴定其为欧文氏菌.结论:菌株B为欧文氏菌,是鲜切青椒的优势腐败菌.     

Carotenoid composition and vitamin A activity of medicinally important green leafy vegetables

Carotenoid composition of green leafy vegetables (GLVs, n = 30) with medicinal value was analyzed by HPLC; vitamin A activity (as retinol equivalent, RE) of provitamin A carotenoids was calculated. Results show that among GLVs studied, the level of β-carotene (50–130 mg/100 g dry wt) was higher in nine GLVs than other carotenoids while lutein (50–187 mg/100 g dry wt) and zeaxanthin (1–5 mg/100 g dry wt) were higher in 12 GLVs than other xanthophylls. α-Carotene was detected only in nine GLVs, ranging from 1 to 37 mg/100 g dry wt. Interestingly, Chenopodium album, Commelina benghalensis and Solanum nigrum were found to contain higher levels of both lutein and β-carotene in the range of 84–187 and 50–115 mg/100 g dry wt, respectively. The values of retinol equivalents (RE) ranged from 641 to 19101 and were higher (>10,000) in six GLVs of the 30. The results demonstrate that GLVs studied contained higher levels of RE and lutein.     

鲜切青椒优势腐败菌的分离纯化及鉴定

目的:筛选鲜切青椒中的优势腐败菌,揭示其腐败能力,并进行初步鉴定。方法:以北京地区\     

In vitro bioavailability of calcium and iron from selected green leafy vegetables

The objective of the present investigation was to analyze the relative influence of oxalic acid, phytic acid, tannin and dietary fiber on in vitro availability of iron and calcium from green leafy vegetables (GLV). Thirteen GLV were selected and analyzed for iron, calcium, oxalic acid, phytic acid, tannin and dietary fiber contents using standard methods. The bioavailability of calcium and iron in the GLV was estimated by equilibrium dialysis. Oxalic acid content was less than 1 g kg^?1 in four greens and ranged between 1.22 to 11.98 g kg^?1 in the remaining. Dietary fiber ranged from 19.5 to 113.7 g kg^?1. Tannin content ranged between 0.6138 and 2.1159 g kg^?1 with the exception of two GLV that had 0.1332 and 14.8619 g kg^?1. Four GLV were found to have approximately 40% bioavailable iron, while the others were in the range of 6–30%. In vitro available calcium was less than or equal to 25% in eight GLV and between 34% and 52% in five GLV. Multiple regression analysis revealed that these factors together accounted for 53% (r² = 0.53) and 45% (r² = 0.45) inhibition of iron and calcium absorption, respectively. These findings infer that calcium and iron availability is influenced by the constituents present in the GLV. Copyright © 2006 Society of Chemical Industry     

Protein and mineral contents of green leafy vegetables consumed by sokoto population

Six green leafy vegetables used extensively in food preparations in northern Nigeria were analysed. Crude protein and ash contents varied from 13.1 to 29.2% and 7.0 to 18.6% respectively. ‘Lalo’ (Corchorus Sp.) had the highest content of sodium (0.31%), iron (0.31%) phosphorus (0.48%) and magnesium (0.47%). There was a significant positive correlation between phosphorus and sodium (r=0.97**), phosphorus and iron (0.81*) and calcium (0.81*) contents.     

Carotenoid composition and vitamin A value of some native Brazilian green leafy vegetables

The composition of carotenoids in five native Brazilian leafy vegetables was determined. The ranges of total carotenoid contents of Amaranthus viridis, Lepidium pseudodidymum, Xanthosoma spp., Sonchus oleraceus , and Portulaca oleracea were 347–468, 237–280, 225–361, 149–334 and 71–109 μg g⁻¹, with lutein and β-carotene predominating. The mean β-carotene contents (μg⁻¹) and vitamin A values (retinol equivalents RE_g⁻¹) were 110 and 18.4, 84.6 and 14.1, 67.3 and 11.2, 62.9 and 10.5, 29.8 and 4.99, respectively. The leaves contained 54–61% of lutein plus violaxanthin, 24–34% of β-carotene, 10–14% of neoxanthin and traces of zeaxanthin and α-crypto-xanthin. The native leafy vegetables were richer sources of provitamin A than the cultivated leafy vegetables analysed previously, justifying their commercial production.     

温度对鲜切马铃薯生理和品质的影响

测定了鲜切马铃薯在2、12、25℃3个贮藏温度下生理指标和品质指标的变化。结果表明:与12℃和25℃相比,2℃贮藏条件显著抑制了鲜切马铃薯的失重率和呼吸强度,延缓其衰老进程;维持了较高的白度、硬度和可溶性固形物含量,保持了原有品质;有效地抑制了多酚氧化酶(PPO)和过氧化物酶(POD)的活性,从而减缓了鲜切马铃薯的褐变。为低温条件下鲜切马铃薯的贮藏提供了理论依据。