Use of 1‐methylcyclopropene to extend the postharvest life of lettuce

This study examined the effect of fumigation of iceberg lettuce with 1‐methylcyclopropene (1‐MCP) at 0.1–1 µl l^?1 for 1–5 h on the storage life at 5 °C in air containing 0.1 µl l^?1 ethylene. 1‐MCP extended the storage life of shredded lettuce at all concentrations, with the optimal treatment being fumigation with 0.1 µl l^?1 1‐MCP for 1 h at 5 °C, which resulted in an extension in storage life of about 50% over untreated lettuce. Application of this treatment to whole lettuce heads resulted in a 100% increase in storage life. 1‐MCP thus appears to be of considerable commercial potential for the lettuce industry. © 2002 Society of Chemical Industry     

Root-zone temperature and nitrogen affect the yield and secondary metabolite concentration of fall- and spring-grown, high-density leaf lettuce

BACKGROUND: Understanding the effects of temperature and nitrogen levels on key variables, particularly under field conditions during cool seasons of temperate climates, is important. Here, we document the impact of root‐zone heating and nitrogen (N) fertility on the accumulation and composition of fall‐ and spring‐grown lettuce biomass. A novel, scalable field system was employed. RESULTS: Direct‐seeded plots containing a uniform, semi‐solid, and nearly stable rooting medium were established outdoors in 2009 and 2010; each contained one of eight combinations of root‐zone heating (?/+) and N fertility (0, 72, 144, and 576 mg day^?1). Root‐zone heating increased but withholding N decreased biomass accumulation in both years. Low N supplies were also associated with greater anthocyanin and total antioxidant power but lower N and phosphorus levels. Tissue chlorophyll a and vitamin C levels tracked root‐zone temperature and N fertility more closely in 2009 and 2010, respectively. CONCLUSIONS: Experimentally imposed root‐zone temperature and N levels influenced the amount and properties of fall‐ and spring‐grown lettuce tissue. Ambient conditions, however, dictated which of these factors exerted the greatest effect on the variables measured. Collectively, the results point to the potential for gains in system sustainability and productivity, including with respect to supplying human nutritional units. Copyright © 2011 Society of Chemical Industry     

Pepper antioxidant composition as affected by organic,low‐input and soilless cultivation

BACKGROUND: The aim of this work was to study the effects of organic (O), low‐input (LI) and soilless (SL) cultivation on pepper nutritional quality and antioxidant activity. For that, 24 commercial greenhouses were selected following strict criteria in order to reduce the influence of environmental conditions and realistically reflect commercial production systems. Fruits were harvested at two maturity stages (green and red) and three harvesting times during two consecutive years. RESULTS: Pepper antioxidant activity mainly stemmed from water‐soluble compounds, including organic acids and phenolic compounds. Only some differences in sugars and malic and citric acid concentrations were detected between the O and LI systems. Sugars, phenolic compounds, ascorbic acid and hydrophilic antioxidant activity were higher in the SL system. In spite of these differences, overall differences between harvesting times or between years were far greater than those due to the cropping system. CONCLUSION: The main differences in the nutritional quality of pepper fruits were observed between the soil (O and LI) and SL (the most favourable) systems. The results highlight the importance of comparing different harvesting times and years in order to study the effect of cropping system on a specific crop. Copyright © 2009 Society of Chemical Industry     

Physiological optimality,allocation trade‐offs and antioxidant protection linked to better leaf yield performance in drought exposed mulberry

BACKGROUND: Mulberry (Morus spp. L.), usually linked to silkworm rearing, is now considered as a potential forage for livestock feeding and has great potential in world agriculture. Trait‐based investigations for leaf yield stability in mulberry under water stress have not been studied extensively. The present study aims to identify candidate traits conferring leaf yield stability in mulberry under drought. RESULTS: Four popular, indigenous mulberry cultivars (Morus indica L. cvs AR‐12, K‐2, M. Local and V‐1) were investigated. Low leaf temperature (T_l), higher internal/ambient CO₂ ratios (C_i/C_a), greater stomatal conductance to CO₂ (g_s) and stability in photosystem II efficiency were associated with better net photosynthetic rates (P_n) in V‐1, generating maximum leaf yield when compared to other drought‐exposed cultivars. Increased accumulation of foliar α‐tocopherol and ascorbic acid–glutathione pool, associated with higher carotenoids, proline and glycine betaine, facilitated lower lipid peroxidation and better leaf yield in V‐1 under drought. CONCLUSION: Minimal plasticity in photosynthetic gas exchange traits and better quantitative growth characteristics were attributed to leaf yield stability under drought. Lower photoinhibition, stabilized photochemistry, effective osmoregulation and enhanced activity of foliar antioxidants extensively contributed to drought tolerance and higher leaf yield in mulberry. Copyright © 2010 Society of Chemical Industry     

Dynamic rheology of structural development in starch/decolourised hsian‐tsao leaf gum composite systems

The gelling process of decolourised hsian‐tsao leaf gum (dHG)/starch mixtures was monitored as a function of starch/gum ratio and starch type using a dynamic rheometer. It was found that the gelling process followed first‐order kinetics. At starch/gum ratios of 5:1, 4:2 and 3:3, dHG interacted with starch synergistically, resulting in a marked increase in storage modulus (G′). Both the gelling reaction rate constant and plateau G′ value as a function of starch/dHG ratio showed a maximum at a certain starch/gum ratio. These results indicated that a suitable starch/dHG ratio could facilitate the formation of a three‐dimensional network structure and the conversion of chains in the sol fraction into a gel. The maximum G′ value reached depended on the unique chemistry of each starch. Mixed systems with tapioca starch generally showed lower plateau G′ values than mixed systems with wheat or corn starch, possibly owing to the lower amylose content of tapioca starch. © 2002 Society of Chemical Industry     

Ethanolic Noni (Morinda citrifolia L.) leaf extract dechlorophyllised using sedimentation process: Antioxidant,antibacterial properties and efficacy in extending the shelf-life of striped catfish slices

Antioxidant and antimicrobial activities of ethanolic noni leaf extract (ENLE) without and with chlorophyll removal by sedimentation method were comparatively investigated. Total chlorophyll content was reduced by 82% in the top fraction (CR-ENLE) collected after 24 h at 4 °C as compared to that of ENLE. Antioxidant and antimicrobial activities were lower in the bottom fraction rich in chlorophyll (Chlo-ENLE) than others (P < 0.05). Based on the microbiological limit, the shelf-life of striped catfish slices pre-treated with 400 mg kg⁻¹ C-R-ENLE was extended to 9 days as compared to the 3 days recorded for the control (without pre-treatment). Slices treated with CR-ENLE had lower lipid oxidation than those treated with ENLE during refrigerated storage (P < 0.05). The sedimentation process was therefore a potential green method for producing ENLE having improved antioxidant and antimicrobial activities without green colour. It can be used as a natural additive for shelf-life extension of fish slices.     

Evaluation of antioxidant activity of olive leaf extract obtained by ultrasound-assisted extraction and their antimicrobial activity against bacterial pathogens from food

The aim of the present study was to evaluate and compare the phenolic content and antioxidant and antimicrobial properties of olive leaf extracts obtained by ultrasound-assisted extraction (UAE) and conventional extraction (CSE). UAE of olive leaf extracts yielded a higher total phenolic content (TPC) and total flavonoid content (TFC) of 14.31% and 19.50%, respectively. Higher antioxidant activities were found from the extracts prepared with UAE (for 18.5%, 12.5%, 10.9% and 17.6% higher determined by DPPH, ABTS, FRAP and CUPRAC methods, respectively). Good antibacterial inhibitory activity (as MIC and MBC) was observed against both Y. enterocolitica and S. aureus (1.40 ± 0.40 mg mL⁻¹ and 4.00 ± 1.60 mg mL⁻¹, respectively) with the extract prepared with UAE. In conclusion, olive leaf extracts prepared with UAE exhibited higher antioxidant and antimicrobial activities against common food-borne pathogens than CSE extracts and thus could be beneficial in ensuring food quality and food safety.     

Cognitive enhancement and neuroprotection by catechin‐rich oil palm leaf extract supplement

BACKGROUND: Catechin‐rich oil palm (Elaeis guineensis) leaf extract (OPLE) has good cardiovascular and phytoestrogenic properties. The OPLE (0.5 g day^?1) was supplemented to young, healthy, adult human volunteers, and their cognitive learning abilities were compared to placebo‐controlled groups (N = 15). Their short‐term memories, spatial visualisations, processing speeds, and language skills, were assessed over 2 months by cognitive tests computer programs. RESULTS: Relative to the controls, volunteers taking OPLE had improved (P < 0.05) short‐term memory, after 1 month of intervention which became highly significant (P < 0.005) after 2 months. The spatial visualisation ability and processing speed improved (P < 0.05) after 2 months consumption. The dietary OPLE showed neuroprotection in nitric oxide‐deficient rats. The mechanisms involved systemic and cellular modulations that eventually enhance neuron survival. The longer the duration of OPLE consumption, the more significant was the enhancement, as shown for short‐term memory. CONCLUSION: This is the first report on the cognitive‐enhancing effects of dietary OPLE in humans. The computer‐assisted cognitive tests were simple, low in cost, errors and man hours, and hence are better than conventional cognitive test methods. In rats, the equivalent OPLE dose showed brain antioxidant enzymes modulating properties and neuroprotection under nitric oxide deficiency, with possibly neurogenesis in normal rats. This supported the effects in humans. © 2012 Society of Chemical Industry     

(+)‐Catechin and (−)‐epicatechin levels of concentrated and ready‐to‐drink grape juices through storage

Commercial concentrated Concord (CCJ) and Isabel (CIJ) grapes juices were stored at 4–5 °C while pasteurised ready‐to‐drink juices of the same grape cultivars (PCJ and PIJ) were kept at 20–25 °C under indirect light for 10 months, simulating industrial storage conditions. (+)‐catechin preservation during storage ranged between 63% (PCJ) and 52% (PIJ); (?)‐epicatechin retention was of 32% (CCJ) and 15% (CIJ). Total phenols retention ranged from 93% (CCJ) to 84% (PCJ) and radical scavenging activity (RSA) from 87% (PIJ) to 85% (CCJ and PCJ). Concentrated juices showed higher monomeric flavan‐3‐ols amounts and CCJ depicted superior phenolic contents. PIJ yielded the highest RSA during storage per phenolic unit. Process and storage impacted flavan‐3‐ols and not total phenolics and RSA during 10‐month ageing.     

Effects of light level, time of harvest and position within field on the variability of tissue nitrate concentration in commercial crops of lettuce (Lactuca sativa) and endive (Cichorium endiva)

Seven commercial crops of lettuce and one crop of endive were sampled in order to study the variability in plant tissue nitrate concentration (TNC). Assuming that an appropriate sampling pattern was employed, ten plants were sufficient to give an acceptable estimate of the mean TNC. Short-term shading (24-48 h) had no significant effects on mean TNC, unlike the increase in TNC known to occur following dull periods 10-14 days before harvest. The effect on TNC of time of day harvested was significant, but there was no obvious pattern of diurnal variation. Averaged over all experiments, the coefficient of variation for TNC was in the order of 35%. Increasing the sample size from ten to 40 plants would only be expected to decrease the standard error of measurement of TNC from 16 to 12% of the mean because of the underlying analytical error, which would remain constant.     

Water‐use efficiency in grapevine cultivars grown under controlled conditions: effects of water stress at the leaf and whole‐plant level

Background and Aims: Improving water‐use efficiency (WUE) is desirable for future grapevine growth and grape production, especially in Mediterranean areas where water is predicted to be limiting. Understanding the genetic variability in WUE is important to identify the most appropriate cultivars to be used in semi‐arid areas. Most previous studies have focused at leaf‐level WUE, while information on whole‐plant level is scarce. This study explored the genetic variability of grapevine in whole‐plant WUE (WUE_WP) to determine whether several leaf WUE (WUE_l) indicators are suitable as proxies of WUE_WP. Methods and Results: Three similar experiments were performed to compare WUE in up to eight different grapevine cultivars under irrigation and water‐stress treatments. Although WUE_l and WUE_WP varied with cultivar and treatment, WUE_l was not a reliable parameter to predict WUE_WP. Conclusions: Large variability in WUE_WP between grapevine cultivars was observed, although this variability was not described by leaf‐level indicators of WUE. Significance of the Study: This study showed that the large variability existing for WUE_WP in different cultivars offers an potential method for selecting the more suitable cultivars to grow in water‐scarce viticulture areas, although WUE_l is not reliable for estimating WUE_WP.     

Antioxidant and anticancer capacity of saponin‐enriched Carica papaya leaf extracts

The papaya (Carica papaya) leaf (PL) contains high levels of saponins and polyphenolic compounds, and historically, it has been used as a folk medicine for numerous ailments, including cancer. PL is traditionally prepared by hot water extraction; however, optimised extraction conditions have not been assessed. This study optimised conditions for the extraction of saponins from PL and assessed their antioxidant capacity and antipancreatic cancer activity. Optimisation was achieved using response surface methodology. Saponins and total phenolic compounds were assessed for their antioxidant, free radical scavenging, ion‐reducing capacity, and antipancreatic cancer activity. Optimal aqueous extraction conditions were 85 °C, 25 min. and a water‐to‐leaf ratio of 20:1 mL g^?1. Ethanol extracts demonstrated higher antioxidant, free radical scavenging and ion‐reducing capacity, as well as antipancreatic cancer activity. This study revealed that the PL contains numerous bioactive compounds, with significant anticancer activity warranting further studies on the isolation and characterisation of individual bioactive compounds from the PL.