Effects of selenium addition on minimally processed leafy vegetables grown in a floating system

BACKGROUND: In recent years the consumption of minimally processed leafy vegetables has been increasing. At the same time food quality and its effects on human health have become crucial issues. Since selenium (Se) is an important microelement due to its ability to defend human organisms against free radicals, we investigated the effects of Se on chicory and lettuce production, and assessed the feasibility of a floating system as a method of producing Se‐enriched vegetables. RESULTS: The addition of 0.5 and 1.0 mg Se L^?1 to the nutrient solution resulted in an increase in the selenium concentration in the leaves, which had a positive effect on the plant yield. Selenium was generally effective in decreasing the production of ethylene and phenylalanine ammonia lyase (PAL) activity, even though a seasonal effect seemed to be present, consequently improving the quality of leafy vegetables and the shelf life in both species. The amount of Se accumulated in plants grown in the nutrient solution containing 0.5 mg Se kg^?1 could provide the rational Se intake for human nutrition in accordance with the recommended dietary allowance (RDA) guidelines. CONCLUSIONS: The addition of Se in a nutrient solution can be a useful system for providing enriched leafy vegetables. The floating system can be used to modulate the availability of Se in nutrient solutions and to grow vegetables with the optimal Se content for human health. Copyright © 2009 Society of Chemical Industry     

The impact of fermentation at elevated temperature on quality attributes and biogenic amines formation of low-salt fermented fish

To accelerate fermentation and improve quality of fermented fish, the impact of fermentation at elevated temperature on physicochemical, microbiological and flavour characteristics, as well as biogenic amines (BAs) accumulation of low-salt fermented fish was investigated. Results showed that increasing temperature at later stage significantly promoted the growth of lactic acid bacteria, retarded the reduction of yeast and increased the titratable acidity, while staphylococci and enterobacteriaceae were inhibited to higher extent when fermented at elevated temperature. BAs contents in samples fermented at 30 °C during later stage were lower than those in the group fermented at 25 °C for 28 days, and the lowest values were observed in the sample initially fermented at 25 °C for 10 days followed by fermentation at 30 °C for 18 days. Furthermore, fermentation at elevated temperature at later stage favoured the formation of desired volatile flavour compounds. Results suggested that fermentation at elevated temperature at later stage could reduce BAs accumulation and enhance quality attributes of low-salt fermented fish.     

Effect of different stocking densities during transport on welfare and meat quality in Danish slaughter pigs

Four stocking densities (0.35, 0.39, 0.42 and 0.50 m² per 100 kg pig) were investigated under Danish early Autumn conditions (16–24 ° C) in a study of the effect of transport conditions on pig welfare and meat quality. Two transports were carried out for each stocking density, the two producers concerned delivering pigs to the upper and lower tiers, respectively, of a specialist pig transport vehicle. Total average journey time was 2 hr 39 min and total average transport time 1 hr 47 min. After arrival at the factory pigs were lairaged in groups of 15 for about hr and then slaughtered using minimal stress with group CO₂-stunning. Pig behaviour was monitored during transport in the front compartment of the lower tier. Blood samples were taken at slaughter for analysis of creatine phosphokinase, lactate and cortisol and carcasses were evaluated for skin damage and meat quality. Stocking density, as such, had relatively little effect on blood profile or meat quality. Creatine phosphokinase levels were lowest with a stocking density of 0.50 m² and the incidence of unacceptable skin damage was generally lowest with a stocking density of 0.35 m² and highest with 0.42 m². The main source of variation in this experiment was day of transport/slaughter within stocking density so that factors other than stocking density have affected the results obtained. Stocking density had a direct effect on pig behaviour during transport. Giving pigs more space during the short transport did not result in them lying down. On the contrary there was continuous disturbance from other pigs and at 0.42 and 0.50 m² pigs had difficulty maintaining balance, when the vehicle negotiated bends or poor road surfaces. Variations in pig behaviour during transport could account for the observed differences in skin damage.     

The baking quality and protein characteristics of a winter wheat grown at different levels of nitrogen fertilisation

Three samples of field-grown winter wheat (Triticum aestivum cv. Atou) with different protein contents were produced by late application of urea as a nitrogenous fertiliser. Baking tests (a conventional fermentation procedure) indicated that the breadmaking quality of the flours increased as protein content was raised from the lowest to the intermediate level, but that the flours of intermediate and highest protein content were of equivalent breadmaking quality. To compare gluten baking quality independently of protein quantity, loaves were also baked from ‘flours’ reconstituted to equivalent protein levels using the isolated glutens. The flours of low and intermediate protein content yielded glutens of similar baking quality. The gluten derived from the flour of highest protein content gave a lower loaf volume and texture score: subsequent biochemical investigations suggested that this was due to an effect of the relative levels of nitrogen and sulphur available to the plants grown on this particular soil. Analysis of the flours and glutens indicated that the ratio of sulphur:nitrogen fell as grain protein content increased and this correlated with a lower proportion of the sulphur amino acids cyst(e)ine and methionine. Gel electrophoresis studies revealed, in particular, an increase in the proportion of the sulphur-deficient, ω-gliadin species as grain protein content increased. Agarose gel filtration chromatography of the flour and gluten proteins also suggested a correlation between the extent of aggregation of their glutenin components (mediated by disulphide bonds involving cystine residues) and their functional properties. The results of this study suggest that for wheat grown on this particular soil late application of high levels of a nitrogenous fertiliser in the absence of sulphur fertilisation led to a change in the balance between available nitrogen and available sulphur, such that the available sulphur levels became insufficient for ‘normal’ grain development. Nevertheless, the results indicated that considerable alteration in the biochemical characteristics of the flour proteins occurred before gluten baking quality was noticeably affected.     

Effect of soy protein isolate on gel properties of Alaska pollock and common carp surimi at different setting conditions

The effects of soy protein isolate (SPI) on the gel properties of different grade Alaska pollock and common carp surimi at different setting conditions were evaluated and compared. Breaking force and distance of gels decreased with increasing SPI concentrations in direct cook (85 °C for 30 min) and in cook after setting at 30 °C for 60 min conditions. The effect of SPI on gel strength of common carp surimi was less than in Alaska pollock surimi. The breaking force obtained for addition of 10% SPI to Alaska pollock surimi was higher than for surimi alone when cooked after incubation at 50 °C for 60 min. Addition of SPI decreased the whiteness and increased the yellowness of the gel. The gel structure showed that the addition of SPI modified the microstructure of the fish protein gel, thus resulting in surimi with different gelling properties. Copyright © 2004 Society of Chemical Industry     

Microbial and sensory quality of vegetables for soup packaged in different atmospheres

Fresh prepacked vegetables for soup have become very popular on the Italian market, since they are already peeled, cut, washed and ready-to-use. The packaging and the modified atmosphere can prolong their shelf-life and maintain their hygienic, physicochemical and sensory characteristics during storage at + 4°C. The hygienic and sensory quality was evaluated by analysing microbial growth and atmosphere composition at the moment of packaging and at the end or the shelf-life of vegetables prepacked in air on under modified atmospheres, and by determining the browning or blackening of parsley and the loss of carrot exudates. A large number of different groups of microorganisms was found in raw vegetables. In spite of this high starting concentration of microbial flora, the prepackaging systems investigated did not seem to significantly influence their growth during vegetable storage at +4°C. No pathogenic microorganisms were isolated from the prepackaged vegetables. The hygienic quality was similar in all packaging systems used. However, the vegetables packaged in perforated. film kept their sensory characteristics better than those packaged in air or under a modified atmosphere.     

清洗方式对鲜切莴笋品质和农残去除的影响

研究不同清洗方式对鲜切莴笋中的有机磷农药去除作用及对其品质指标的影响。结果表明:次氯酸钙和果蔬清洗机均能去除农药残留,保持鲜切莴笋的品质,其中果蔬清洗机清洗15min,能更有效的去除农药残留,抑制呼吸强度,杀灭微生物。     

不同氮源海藻肥对无土栽培生菜生长及品质的影响

本研究用海带浸泡液复配酰胺态氮、植物氨基酸粉、鱼蛋白三种氮源制成肥料,分别探讨了不同稀释度对生菜生长及品质的影响。结果表明:与改良霍格兰配方对比,氨基酸粉海藻肥稀释倍数为3000 倍时,生菜鲜重、叶绿素、还原糖、蛋白含量分别增加23.21%、4.21%、35.48%、35.71%,硝酸盐含量降低了60.31%;鱼蛋白海藻肥稀释倍数为2000 倍时,生菜鲜重、叶绿素、还原糖、蛋白含量分别增加21.94%、14.81%、15.21%、24.85%,硝酸盐含量降低了57.96%;酰胺态氮(尿素)海藻肥稀释倍数为1800 倍时,生菜鲜重、还原糖、蛋白含量分别增加15.25%、16.31%、8.33%,硝酸盐和叶绿素含量分别降低了2.10%、15.09%。研究结果表明氨基酸粉海藻肥最适宜作为生菜无土栽培的有机肥。     

黄淮小麦RVA参数变异及其品质分析

选用我国黄淮麦区141份主要小麦品种(系),探讨了它们的糊化特性遗传变异及其它主要品质的相关分析.结果表明:我国黄淮小麦品种糊化特性表现出较大的变异,峰值粘度、低谷粘度和衰减度等性状的变异范围分别为1196-4241cp、409-2834cp、548-1680cp,15份材料的峰值粘度、衰减度分别超过3000cp和1300cp.说明通过遗传改良我国小麦糊化特性潜力是很大的.淀粉膨胀势与糊化特性的大多数指标均达到极显著相关,在早代单株选择时,用膨胀势代替糊化测定是可行的.     

江苏省不同季节蔬菜农药残留状况调查分析

目的调查分析近3年江苏省内主要蔬菜生产县(区)不同季节蔬菜农药残留状况。方法按照GB2763-2016《食品安全国家标准食品中农药最大残留限量》对蔬菜中农药残留进行检测并对检测结果进行判定。结果第一季度的蔬菜农药残留检出率和超标率是全年4个季度最高的;叶菜类蔬菜农药残留风险是各类蔬菜中较大的且各年度间变异小;限用农药残留风险比非禁限用农药大,非禁止限用农药中腐霉利、啶虫脒残留风险较大。结论江苏省不同季节蔬菜农药残留存在一定风险,有必要在今后工作中进行原因排查和分析,以便于在发现的风险关键点加强农产品安全监测。     

黑果枸杞与5种果蔬中花色苷组成及体外抗氧化活性比较

目的:评价黑果枸杞等6种不同花色苷来源的植物材料的花色苷组成含量及体外抗氧化活性,为花色苷的利用和具有较强抗氧化活性植物资源的筛选提供参考。方法:取黑果枸杞等6种不同花色苷来源的植物材料,采用分光光度法、HPLC-MS法分析测定黑果枸杞花色苷含量及主要组成,用DPPH、ABTS和FRAP法分析其体外抗氧化活性。结果:黑果枸杞等6种不同花色苷来源的植物材料总花色苷含量的变化幅度为0.21².26mg/g鲜果。其中黑果总花色苷含量最高,花色苷含量分别是葡萄、树莓、紫甘蓝、蓝莓和紫薯的10.72、4.91、1.91、1.75、4.45倍。黑果枸杞花色苷的主要组分为矮牵牛素衍生物,有别于其他所测果蔬材料,其抗氧化活性也最高。结论:较之5种花色苷含量较高的天然果蔬材料,黑果枸杞中花色苷主要组分与之差异很大,总花色苷含量和抗氧化活性总体都较高,是较好的开发功能性食品的资源。      

Application of the general stability index method to predict quality deterioration in bighead carp (Aristichthys nobilis) heads during storage at different temperatures

A freshness index called the global stablity index (GSI) applicable to follow the variation of multi-quality indices of bighead carp (Aristichthys nobilis) heads during different temperatures storage was evaluated. Quality indices (sensory score, total aerobic counts, volatile base nitrogen, and K value) were estimated and calculated into the single parameter GSI at −3, 0, 3, 9 and 15 °C. GSI was then kinetically modeled to describe the dependency of GSI with temperature and storage time. The calculated data of GSI were satisfactorily described by a zero order kinetic model. The activation energy (E_A) and the corresponding pre-exponential constant (k₀) of GSI were 85.61 kJ/mol and 1.14 × 10¹⁵, respectively. Relative errors between predicted and observed GSI values were all below 10% before the 15th day. Thus, the established model based on GSI could effectively predict the freshness of bighead carp heads at the range of −3 and 15 °C during different temperatures storage.     

密度和施氮量对沿海滩涂中度盐碱地蓖麻磷素吸收的影响

以淄蓖5号和云蓖泰国202为试验品种,研究沿海滩涂中度盐碱地不同种植密度和施氮量条件下蓖麻磷吸收的特点及与产量的关系。结果表明,蓖麻苗期磷吸收百分率和吸收速率很低,蕾期显著增加,开花期达到高峰,花果期和灌浆成熟期逐渐降低。与淄蓖5号相比,云蓖泰国202在苗期吸收百分率和吸收速率较低,蕾期差异不大,开花期明显增高,灌浆成熟期仍保持着较高的磷吸收量。淄蓖5号在种植密度13 000株.hm-2、施氮量120kg.hm-2条件下产量最高,每生产100kg的蓖麻籽吸收磷1.23kg。云蓖泰国202在种植密度16 000株.hm-2,施氮量120kg.hm-2的条件下产量最高,每生产100 kg的蓖麻籽吸收磷1.10～1.13kg。由于盐碱地土壤中的有效磷含量较低,在本试验条件下即使施用50kg.hm-2的P2O5仍不能满足蓖麻对磷的需要,要进一步提高蓖麻产量还需加大磷肥投入。     

Impact of different temperature abuse scenarios on sensory quality and off-odour formation in ready-to-eat salad leaves

Packages of ready-to-eat (RTE) wild rocket and lettuce baby leaves were subjected during 8 days of cold storage to a chronic temperature abuse (CTA) at sub-optimal storage temperature (10 °C) or to a short-term (6 h) abuse at ambient temperature (STA) to evaluate the impact of two temperature abuse scenarios on gas composition within the packages, leaf sensory quality and volatile organic compounds (VOCs). In both species, the CTA scenario had a markedly higher impact on gas composition, sensory quality and off-odour formation than the STA, and the limit of sensory acceptability was reached in the CTA scenario 4 days or more earlier than in the STA. Sulphur compounds were the main responsible for off-odour perception in both leafy salads. Results from the present study may be useful in the assessment of critical points in the cold chain of RTE fresh produce and in prioritising actions towards improved cold-chain management.     

Timing and rate of nitrogen application influence grain quality and yield in maize planted at high and low densities

BACKGROUND: Efficient use of nitrogen (N) is considered one of the most important inputs needed for increasing grain quality and crop productivity. Hypothesis was that grain quality and yield of maize (Zea mays L.) in north‐west Pakistan are enhanced by increasing the rate of N, and that response to applied N is greater with an increase in the number of N split applications at high plant density compared to low density. RESULTS: Field experiments were carried out on maize (cv. Azam) in summer 2002 and 2003 consisting of two planting densities and three N rates as main plots, and six split N applications as sub‐plots. Year 1 had higher shelling percentage and stover yield (SY). Harvest index (HI) decreased but SY increased with increase in plant density. Increase in N rate and number of split N applications increased grain weight and protein content, HI and SY. CONCLUSION: The highest N rate in four to five split applications increased maize grain quality and yield at both densities. Maize response to the interactive effect of year × plant density, year × N rate, and year × N timing suggests zonal specific effective N management practices for sustainable maize production in different agro‐ecological zones. Copyright © 2009 Society of Chemical Industry     

Quality of fresh‐cut baby spinach grown under a floating trays system as affected by nitrogen fertilisation and innovative packaging treatments

BACKGROUND: Alternative techniques for cultivation of leafy vegetables such as a floating tray system and unconventional gas mixtures for post‐harvest active modified atmosphere packaging (MAP) could be of interest in the minimally processed vegetable industry. RESULTS: The combined effect of three pre‐harvest fertilisation doses (8, 12 or 16 mmol N L^?1) and three post‐harvest MAP conditions (passive, super‐atmospheric or N₂O‐enriched) on the main quality attributes of fresh‐cut baby spinach leaves throughout 10 days at 5 °C was studied. After 8 days of shelf life, spinach leaves fertilised with 8 and 16 mmol N L^?1 and stored under N₂O‐enriched MAP showed the lowest microbial growth, with good sensory quality. Such combined treatments also preserved the total antioxidant capacity sampled at harvest (8 g ascorbic acid equivalent antioxidant capacity kg^?1 f.w.). A decrease of 10–20% in total vitamin C content regardless of N fertilisation and packaging treatment was found during shelf life. Total phenolics content at harvest was 2 g gallic acid equivalents kg^?1 f.w., which was slightly decreased or preserved during shelf life while total chlorophylls were preserved for all treatments assayed around 550 mg kg^?1 f.w. CONCLUSION: No clear effect of fertilisation doses was observed during post‐harvest storage on overall quality of fresh‐cut baby spinach leaves, while N₂O‐enriched atmospheres seems to be a promising alternative to passive MAP for extending shelf life. Copyright © 2010 Society of Chemical Industry     

不同生长发育阶段三种野菜中硝酸盐、亚硝酸盐及Vc的含量

测定菜蕨、刺苋、苣荬菜等3种野菜不同发育阶段叶中的硝酸盐、亚硝酸盐和Vc的含量,实验结果分析可知:提琴头期、幼叶期、成熟叶期的菜蕨和幼苗期、营养生长期、果期的苣荬菜为一级蔬菜,可生食、盐渍和熟食;半成熟叶期的菜蕨、初花期的苣荬菜为二级蔬菜,不可生食,可盐渍和熟食;盛花期的苣荬菜,幼苗期、营养生长期、初花期和果期的刺苋属于三级蔬菜,不可生食、盐渍,可熟食;初果期(盛花期)的刺苋属于四级蔬菜,应避免食用或限量熟食。