T. J. O'Hare

The effects of 1-methylcyclopropene on the shelf life of minimally processed leafy asian vegetables

The effect of 1-methylcyclopropene (1-MCP) on shelf life and the ethylene sensitivity of detached leaves from six leafy asian vegetables (Chinese mustard, choy sum, garland chrysanthemum, mibuna, mizuna and tatsoi) commonly used in minimal processing was examined. All vegetables studied were significantly affected by the presence of 1 μl/l ethylene. This reduction was primarily due to yellowing except in mizuna and mibuna. In the absence of ethylene, 1-MCP treatment only increased shelf life for mizuna and tatsoi (21 and 67% increase, respectively). In contrast, 1-MCP treatment in the presence of ethylene significantly protected Chinese mustard, choy sum, garland chrysanthemum and tatsoi. 1-MCP may, therefore, be ideal for use on minimally processed leafy asian vegetables in situations of co-storage or co-retail with ethylene-producing commodities.

Postharvest physiology and storage of rambutan

Abstract Rambutans ( Nephelium lappaceum L.) are harvested when the fruit have reached optimum visual and organoleptic quality. The fruit are non-climacteric with little change in total soluble solids or titratable acidity after harvest. Rambutans rapidly deteriorate unless proper handling techniques are employed. Visual appearance can be maintained if moisture loss (largely from the spinterns) is minimised (95% relative humidity) and the fruit are refrigerated (7–10 °C, depending on cultivar). Under these conditions, rambutans have a storage life of approximately 10–15 days. Postharvest pulp quality and disease development are generally stable under refrigeration until after fruit have become visually unacceptable from chilling injury. Chilling injury is confined to the skin and is characterised by a colour change from red to maroon. Colour deterioration can be further retarded (three–four days) by storage under enhanced carbon dioxide atmospheres (9–12%). Further study into maintaining visual appearance of rambutans is needed before shelf-life can be extended.

Epithiospecifier protein activity in broccoli: the link between terminal alkenyl glucosinolates and sulphoraphane nitrile.

The chemical nature of the hydrolysis products from the glucosinolate-myrosinase system depends on the presence or absence of supplementary proteins, such as epithiospecifier proteins (ESPs). ESPs (non-catalytic cofactors of myrosinase) promote the formation of epithionitriles from terminal alkenyl glucosinolates and as recent evidence suggests, simple nitriles at the expense of isothiocyanates. The ratio of ESP activity to myrosinase activity is crucial in determining the proportion of these nitriles produced on hydrolysis. Sulphoraphane, a major isothiocyanate produced in broccoli seedlings, has been found to be a potent inducer of phase 2 detoxification enzymes. However, ESP may also support the formation of the non-inductive sulphoraphane nitrile. Our objective was to monitor changes in ESP activity during the development of broccoli seedlings and link these activity changes with myrosinase activity, the level of terminal alkenyl glucosinolates and sulphoraphane nitrile formed. Here, for the first time, we show ESP activity increases up to day 2 after germination before decreasing again to seed activity levels at day 5. These activity changes paralleled changes in myrosinase activity and terminal alkenyl glucosinolate content. There is a significant relationship between ESP activity and the formation of sulforaphane nitrile in broccoli seedlings. The significance of these findings for the health benefits conferred by eating broccoli seedlings is briefly discussed.

Differing mechanisms of simple nitrile formation on glucosinolate degradation in Lepidium sativum and Nasturtium officinale seeds

Glucosinolates are sulphur-containing glycosides found in brassicaceous plants that can be hydrolysed enzymatically by plant myrosinase or non-enzymatically to form primarily isothiocyanates and/or simple nitriles. From a human health perspective, isothiocyanates are quite important because they are major inducers of carcinogen-detoxifying enzymes. Two of the most potent inducers are benzyl isothiocyanate (BITC) present in garden cress (Lepidium sativum), and phenylethyl isothiocyanate (PEITC) present in watercress (Nasturtium officinale). Previous studies on these salad crops have indicated that significant amounts of simple nitriles are produced at the expense of the isothiocyanates. These studies also suggested that nitrile formation may occur by different pathways: (1) under the control of specifier protein in garden cress and (2) by an unspecified, non-enzymatic path in watercress. In an effort to understand more about the mechanisms involved in simple nitrile formation in these species, we analysed their seeds for specifier protein and myrosinase activities, endogenous iron content and glucosinolate degradation products after addition of different iron species, specific chelators and various heat treatments. We confirmed that simple nitrile formation was predominantly under specifier protein control (thiocyanate-forming protein) in garden cress seeds. Limited thermal degradation of the major glucosinolate, glucotropaeolin (benzyl glucosinolate), occurred when seed material was heated to >120 degrees C. In the watercress seeds, however, we show for the first time that gluconasturtiin (phenylethyl glucosinolate) undergoes a non-enzymatic, iron-dependent degradation to a simple nitrile. On heating the seeds to 120 degrees C or greater, thermal degradation of this heat-labile glucosinolate increased simple nitrile levels many fold.

Key Role of Fe2+ in Epithiospecifier Protein Activity

The chemical nature of the hydrolysis products from the glucosinolate-myrosinase system depends on the presence or absence of supplementary proteins such as epithiospecifier proteins (ESPs). ESPs promote the formation of epithionitriles from terminal alkenyl glucosinolates and, as recent evidence suggests, simple nitriles at the expense of isothiocyanates. From a human health perspective isothiocyanates are the most important because they are major inducers of carcinogen-detoxifying enzymes. Fe(2+) is an essential factor in ESP activity, although several recent studies have highlighted discrepancies in the understanding of the ESP-iron interaction. To investigate further the role iron species play in regulating ESP activity, four ESP-containing seedpowders were analyzed for ESP and myrosinase activities, endogenous iron content, and glucosinolate degradation products after the addition of iron species, specific chelators, and reducing agents. For the first time this paper shows the effect of these additions on the hydrolysis of individual glucosinolates that constitute the total pool. Aged seeds and 3-day seedlings were also tested to investigate the effects of seed storage and early plant development on iron levels and ESP activity. The four ESP-containing plant systems tested gave two distinctive responses, thus providing strong evidence that ESPs vary markedly in their Fe(2+) requirement for activity. The results also indicated that reduction of ferric to ferrous iron drives variations in ESP activity during early plant development. The reverse oxidation reaction provided a convincing explanation for the loss of ESP activity during seed storage. Aged seeds produced seedlings with substantially lower ESP activity, and there was a concomitant loss in germination rate. It was concluded that manipulation of endogenous iron levels of ESP-containing plants could increase the conversion of glucosinolates to isothiocyanates and enhance potential health benefits.

Screening sweetcorn for enhanced zeaxanthin concentration

BACKGROUND New varieties of fruits and vegetables, with higher carotenoid levels, are being developed to improve the potential health benefits to consumers. To assist the development of a new variety of high zeaxanthin sweetcorn, an analytical screening method was developed, including chromameter measurement of hue angle and optimized extraction for HPLC, and applied to 385 lines of a breeding population and six commercial varieties. RESULTS Saponification had no effect on carotenoid extraction. In the breeding population, carotenoid levels had a wide range with the highest levels of zeaxanthin being 11.9 mg kg(-1) fresh weight, which was at least six times greater than the tested commercial varieties. The regression of hue angle versus zeaxanthin was described by the equation, hue angle = 76.16 + 4.50 x exp(-0.24 x zeaxanthin) + 11.73 x exp(-0.24 x zeaxanthin), r(2) of 0.59. The top 6% of lines, with regards to zeaxanthin (zeaxanthin + beta-cryptoxanthin + beta-carotene) and total carotenoids, all had hue angles <or=84.1 degrees. CONCLUSION The use of a hue angle of 85 degrees as a maximum cut-off for liquid extraction will allow for much increased efficiency in screening further germplasm for high zeaxanthin lines. There appears to be significant opportunity to further increase the zeaxanthin concentration by selecting for lines which preferentially channel carotenoid synthesis towards zeaxanthin.

Effect of ripening temperature on quality and compositional changes of mango (Mangifera indica L.) cv. Kensington

Preclimacteric mangoes (Mangifera indica L.)cv. Kensington were treated with ethylene (200 ¦L/L) for 36 h, then ripened under a range of temperatures from 13 to 30¦C and under 2 diurnal temperature regimes (18/24¦C in 12/12 h and 18/6 h cycles). Fruit were assessed for quality (skin colour, pulp colour, eating quality) and compositional changes over the ripening period. Fruit that was ripened at 18-22¦C achieved the highest quality scores, with all quality parameters reaching a maximum within about 2 days of each other. Diurnal temperature cycling provided no advantage over non-cycled temperatures. Fruit ripened at 13 and 30¦C had lower skin colour quality scores, related to poor carotenoid development and high chloropnyii retention, respectively. The poor carotenoid development at 13¦C also resulted in lower pulp colour quality scores. Eating quality was significantly lower at 13 and 30¦C, related to the slow decline in titratable acidity and poor flavour, respectively. Quality parameters became unsynchronised at 13 and 30¦C, with skin colour quality reaching a maximum 5 days earlier than eating quality at 13¦C, and 3 days later at 30¦C.

Impact of root and shoot temperature on bud dormancy and floral induction in lychee (Litchi chinensis Sonn.)

Potted lychee trees (cv. Tai so) with mature vegetative flushes were grown under three day/night temperature regimes known to induce floral (18/13 °C), intermediate (23/18 °C) and vegetative (28/23 °C) shoot structures. Heating roots respective to shoots accelerated bud-break and shoot emergence, but reduced the level of floral initiation in emergent shoots. At 18/13 °C, root temperatures of 20 and 25 °C decreased the period of shoot dormancy from 9 weeks to 5 and 3 weeks, respectively. A root temperature of 20 °C also increased the proportion of both leafy and stunted panicles to normal leafless panicles, and reduced the number of axillary panicles accompanying each terminal panicle. A root temperature of 25 °C produced only vegetative shoots. At 23/18 °C, heating roots increased the proportion of vegetative shoots and partially emerged buds to leafy and stunted panicles as well as accelerating bud-break. Cooling of roots in relation to the shoot resulted in non-emergence of buds at both 28/23 and 23/18 °C. Bud-break did not occur until root cooling was terminated and root temperature returned to that of the shoot. At 23/18 °C, subsequent emergent shoots had a greater proportion of leafy panicles relative to control trees. At 28/23 °C, all emergent shoots remained vegetative. Lychee floral initiation is influenced by both root and shoot temperature. Root temperature has a direct effect on the length of the shoot dormancy period, with high temperatures reducing this period and the subsequent level of floral initiation. However, an extended period of dormancy in itself is not sufficient for floral initiation, with low shoot temperatures also a necessary prerequisite.

Cultivar affects browning susceptibility of freshly cut star fruit slices

Consumption of freshly-cut horticultural products has increased in the last few years. The principal restraint to using freshly-cut carambola is its susceptibility to tissue-browning, due to polyphenol oxidase-mediated oxidation of phenolic compounds present in the tissue. The current study investigated the susceptibility to browning of star fruit slices (Averrhoa carambola L.) of seven genotypes (Hart, Golden Star, Taen-ma, Nota-10, Malasia, Arkin, and Fwang Tung). Cultivar susceptibility to browning as measured by luminosity (L*) varied significantly among genotypes. Without catechol 0.05 M, little changes occurred on cut surface of any cultivars during 6 hour at 25°C, 67% RH. Addition of catechol led to rapid browning, which was more intense in cvs. Taen-ma, Fwang Tung, and Golden Star, with reduction in L* value of 28.60%, 27.68%, and 23.29%, respectively. Browning was more intense in the center of the slices, particularly when treated with catechol, indicating highest polyphenol oxidase (PPO) concentration. Epidermal browning, even in absence of catechol, is a limitation to visual acceptability and indicates a necessity for its control during carambola processing. Care must be given to appropriate selection of cultivars for fresh-cut processing, since cultivar varied in browning susceptibility in the presence of catechol.

The Effect of Lycopene on the PI3K/Akt Signalling Pathway in Prostate Cancer

Prostate cancer is common in men with very high mortality which is one of leading causes of cancer-related deaths in men. The main treatment approaches for metastasized prostate cancer are androgen deprivation and chemotherapeutic agents. Although there are initial responses to castration, the resistance to the treatment will eventually occur, leading to castration-resistant prostate cancer. The common chemotherapeutic agents for the treatment of prostate cancer are docetaxel and taxane but outcomes of using these drugs have not been satisfactory. Therefore, it is necessary to find better treatment approaches for prostate cancer and to search for compounds that are effective in prostate cancer prevention. Lycopene extracted from tomato and other fruits or plants such as Gac, watermelon, pink grapefruit, pink guava, red carrot and papaya has been shown to be effective on prostate cancer prevention and treatment. The advantage of the application of lycopene for its anti-prostate cancer activity is that lycopene can reach much higher concentration in prostate tissue than other tissues. In this review, the effect of lycopene on PI3K/Akt pathway is summarised, which could be one of major mechanisms for anti-cancer activity of lycopene.