Quality of fresh‐cut tomatoes as affected by salt content in irrigation water and post‐processing ultraviolet‐C treatment

BACKGROUND: There is little information available concerning the effect of sanitizing agents, including ultraviolet (UV‐C) light, on nutritional composition of fresh‐cut produce. In this study, the influence of UV‐C light irradiation (3.2–19.2 kJ m^?2) on the nutritional quality of fresh‐cut tomato cv. Durinta grown under either low (2.4/2.8 dS m^?1) or high (4.9/7.7 dS m^?1) electrical conductivity (EC) of the hydroponic nutrient influx/efflux solution was investigated. RESULTS: When grown under low EC UV‐C light treatment reduced development of microbial population of fresh‐cut tomato, increased phenolic content and delayed degradation of vitamin C after 7 days of storage at 4–6 °C. UV‐C light irradiation had no significant effect on appearance, color or lycopene content of fresh‐cut tomato. In recently harvested intact tomatoes, the lycopene and vitamin C contents were 30% higher in tomatoes irrigated with high EC, whereas the phenolic content was unaffected by the salt treatment. After fresh‐cut processing, phenolic and vitamin C contents of fresh cuts produced from tomatoes treated with high EC decreased by > 10%. This decline was initially accelerated in tomato treated with UV‐C light irradiation. CONCLUSIONS: Our results revealed that fresh‐cut tomatoes are affected dissimilarly by UV‐C treatments, depending on the degree of salt stress undergone by plants before harvest. We determined the impact of a sanitizing procedure on nutritional composition, an effect often overlooked but with great significance to ensure overall quality of fresh produce. Our findings revealed the need for more nutritional studies addressing the effect of multiple stress factors from pre‐harvest to post‐processing stages. Copyright © 2008 Society of Chemical Industry     

Effect of grafting and modified atmosphere packaging on eggplant quality parameters during storage

The physico‐chemical parameters (pH, mechanical firmness and vitamin C) and sensory parameters of grafted and ungrafted eggplant plants were studied in relation to storage time (up to 17 days at 10 °C). Eggplant plants of cultivar ‘Tsakoniki’ were grafted on Solanum torvum and S. sisymbriifolium rootstocks in order to avoid the soil borne disease caused by Verticillium dahliae. The fruits were stored under modified atmosphere packaging (MAP). Vitamin C was negatively affected by grafting it storage, while MAP prolonged the shelf life. Although pH was not affected by grafting but was positively affected by MAP. Flesh firmness was negatively affected by grafting and reduced over storage, but positively affected by MAP. Sensory analysis showed higher ratings of fruits from ungrafted plants for sweetness, acceptance and hardness whereas no difference was detected for overall acceptance. Fruits stored under MAP were better maintained compared with those stored in air.     

Antioxidant compounds in green and red peppers as affected by irrigation frequency,salinity and nutrient solution composition

BACKGROUND: There is a need to encourage more sustainable agricultural practices, reducing inputs of water and fertilisers while minimising any negative impact on fruit quality. The effect of irrigation frequency, salinity and potassium and calcium fertilisation on the content of bioactive compounds and quality attributes of green and red peppers grown with and without substrate was evaluated. RESULTS: Low irrigation frequency and salinity improved the quality attributes (dry matter, soluble solids content and titratable acidity) of pepper. Low irrigation frequency increased vitamin C content by 23% in green peppers, while in red fruits it was not affected. In contrast, total carotenoids and provitamin A only increased in red fruits by 30% and 15%, respectively, as a consequence of low irrigation frequency. When the effect of potassium and calcium doses was investigated, it was shown that a high proportion of potassium increased the vitamin C, provitamin A and total phenolic content of red and green peppers, whereas pepper grown at low calcium doses, presented the highest content in carotenoids and provitamin A. CONCLUSION: Low irrigation frequency and fertilisation with high potassium and low calcium doses improved pepper quality increasing the content of bioactive compounds. Copyright © 2009 Society of Chemical Industry     

Effect of hydrogen peroxide on quality of fresh-cut tomato

ABSTRACT:  The effect of hydrogen peroxide (H₂O₂; 0, 0.1, 0.2, and 0.4 M) on selected nutritional quality of fresh-cut tomato was investigated. Microbial population of tomato slices stored at 10 °C and treated with H₂O₂ was lower than the control by 1-(0.2 and 0.4 M) and 5-log (0.4 M), 3 and 7 d after processing, respectively. Dipping fresh-cut tomato into H₂O₂ resulted in reduced phenolic and antioxidant levels after 7 d in storage by at least 5% and 20%, respectively, and produced an initial decline in vitamin C and lycopene. Change in color values in the H₂O₂ treatments were associated with reduced carotenoid content. Our results confirmed antimicrobial benefits of H₂O₂ but revealed a compromise in antioxidant and carotenoid contents of fresh-cut tomatoes.     

西瓜纤维素的提取及其吸液性能

为得到具有较高吸液性能的天然纤维素,以西瓜为原料,采用化学分离方法对其中纤维素的提取工艺进行了研究。通过单因素实验,研究了提取过程中NaOH质量分数、H2O2质量分数、反应温度、反应时间对西瓜纤维素质量分数的影响,在此基础上进行正交实验,确定了提取西瓜纤维素最佳工艺条件,即NaOH质量分数为4％、H2O2质量分数为10％、反应温度为60℃、反应时间为30min时,西瓜纤维素质量分数最佳,为86.52％。SEM观察表明西瓜纤维素具有特殊的中空结构。红外光谱分析表明提取样品成分主要含有纤维素。吸液倍率测试表明,当水温在40℃、Na+浓度为0.1mol/L时,西瓜纤维素的吸液倍率可以达到85g/g,显著高于天然棉纤维素的吸液倍率（40g/g）。     

Effect of pilot-scale aseptic processing on tomato soup quality parameters

Tomatoes are often processed into shelf-stable products. However, the different processing steps might have an impact on the product quality. In this study, a model tomato soup was prepared and the impact of pilot-scale aseptic processing, including heat treatment and high-pressure homogenization, on some selected quality parameters was evaluated. The vitamin C content, the lycopene isomer content, and the lycopene bioaccessibility were considered as health-promoting attributes. As a structural characteristic, the viscosity of the tomato soup was investigated. A tomato soup without oil as well as a tomato soup containing 5% olive oil were evaluated. Thermal processing had a negative effect on the vitamin C content, while lycopene degradation was limited. For both compounds, high-pressure homogenization caused additional losses. High-pressure homogenization also resulted in a higher viscosity that was accompanied by a decrease in lycopene bioaccessibility. The presence of lipids clearly enhanced the lycopene isomerization susceptibility and improved the bioaccessibility. PRACTICAL APPLICATION: The results obtained in this study are of relevance for product formulation and process design of tomato-based food products.     

Nutritional properties of oat‐based beverages as affected by processing and storage

Oat‐based beverages enriched with vitamins and minerals were produced with common hydrothermal treatments and stored at 22 °C for 64 weeks. The effects of decanting on the retention of native vitamins, minerals and fatty acids, and different UHT holding time (5 s or 20 s) at 140 °C on vitamins were investigated. Fatty acid profile, vitamin retention and dissolved oxygen concentration were monitored during storage. The decanting process caused a 47% increase of vitamin B₆ and a 45–74% loss of phosphorus, zinc, calcium and iron. The steam‐injection UHT treatment caused a 60% loss of vitamin D₃ for both holding times and a 30% loss of vitamin B₁₂ for 20 s. During 1 year of storage, oleic and linoleic acids were stable, whereas linolenic acid decreased only slightly, even in the iron‐enriched variety. The dissolved oxygen concentration increased to a low value of 0.71 mg L^?1 and reached a balance after 16 weeks. Most enriched vitamins except vitamins A, D₃ and B₁₂ were stable during ambient storage. Oat‐based beverages with highly retained vitamins can be manufactured by adding vitamins prior to direct UHT treatment with a shorter holding time. Additionally, iron enrichment of such beverages, without affecting the fatty acid profile, can be achieved by filter sterilisation. Copyright © 2007 Society of Chemical Industry     

Encapsulationof lycopene from watermelon in calcium‐alginate microparticles using an optimised inverse‐gelation method by response surface methodology

Lycopene exhibits strong antioxidant activity due to its unsaturated molecular bonds, which also contributes to its susceptibility for degradation. Encapsulation techniques can reduce lycopene degradation, increasing its potential applications in functional foods and nutraceuticals. The objective of this study was to optimise the encapsulation of lycopene from watermelon in alginate microparticles using the inverse gelation method. Box–Behnken design was used for the optimisation of three variables: concentrations of alginate (w/v %) and CaCl₂ (g L^?1), and gelation time (min). Two types of alginate were investigated (low viscosity and high viscosity) and optimised separately using encapsulation efficiency and loading capacity as responses. Results indicated that the models had a good fit to the experimental data and the optimal conditions varied depending on the type of alginate. In general, particles prepared with low‐viscosity alginate exhibited higher encapsulation efficiency and loading capacity and could be used for further research.     

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     

Yield and quality of early potato cultivars in relation to the use of glufosinate‐ammonium as desiccant

BACKGROUND: Glufosinate‐ammonium (GA) is used for chemical vine killing of potato crop before harvest. Over two years we tested the effect of GA, applied at 0.48 kg ha^?1 of active ingredient, on desiccation of haulms, yield and some qualitative traits of tubers of three cultivars of early potatoes, a typical crop of southern Italy and large areas of the Mediterranean countries. RESULTS: Seven days after treatment desiccation reached 90% of leaves for all cultivars. At harvest, the highest desiccation percentage of haulms was 85% in Spunta. The desiccant did not affect yield in either year during which the analysis was carried out, but it increased the percentage of tubers in the range of 35–70 mm in diameter. In the first year, the treatment decreased dry matter and vitamin C content and increased free sugar concentration in tubers. In the second year, no negative effects on the nutritional traits were observed. Strong differences were found on yield and quality between the two years as a result of the different climatic conditions. CONCLUSION: In the two experiments GA had no influence on yield, but increased the percentage of potato tubers in the 35–70 mm range. From a qualitative standpoint in 2004 the chemical vine‐killing treatment had some negative effects (decreased dry matter and vitamin C content, increased free sugar concentrations), whereas no such negative effects were observed in 2005. Copyright © 2009 Society of Chemical Industry