Emeritus Professor Ronald Wills

This study examined the ability of L-arginine, L-cysteine and L-methionine, to inhibit postharvest senescence of broccoli. Florets were dipped in aqueous solutions of the amino acids at concentrations from 1.0 to 100 mM and stored at 10 °C. A 5 mM dip was found to be optimal in delaying senescence as measured by retention of green colour, vitamin C and antioxidant activity, and a lower level of ethylene production, respiration, weight loss, phenylalanine ammonia lyase (PAL) activity and ion leakage with the benefits being similar for all three amino acids. Arginine, cysteine and methionine have Generally Recognised As Safe (GRAS) status and should have few impediments in obtaining regulatory approval for commercial use if similar effects were found for other leafy vegetables.

The perishable nature of fruit and vegetables requires some technological intervention to maintain quality during handling and marketing. The technology of choice for many years has been use of low temperatures as it is effective in reducing metabolism and hence extend postharvest life. However, refrigerated storage is energy intensive and the growing urgency to reduce international greenhouse gas emissions has created a need for technologies that are more environmentally sustainable but still acceptable to consumers. Ethylene is well known to promote ripening and senes-cence of fruit and vegetables. This presentation will review the existing data that support the potential for managing the concentration of ethylene in the atmosphere around produce in postharvest situations to allow a reduced reliance on refrigeration and thus reduce energy consumption. Methods for managing ethylene levels around produce, and barriers that need to be overcome in order to move from a temperature-based mindset are discussed.

Fresh cut Granny Smith apple and iceberg lettuce were dipped in aqueous solutions of l-arginine at ambient pressure and assessed for browning on the cut surface during storage at 5 °C. Arginine delayed the development of browning and hence extended postharvest life. For apple slices, dipping in 50. mM arginine for 10. min resulted in a 15-fold increase in postharvest life over control slices. For lettuce pieces, the postharvest life was doubled by dipping in 100. mM arginine for 5. min. Arginine was found not to affect the taste of apple slices after a 250. mM dip and was more effective on a concentration basis than calcium ascorbate in inhibiting browning. Further studies are warranted to assess the suitability of arginine as a treatment to inhibit browning of fresh-cut produce.

BACKGROUND: The postharvest life of fresh-cut apple slices is limited by browning on cut surfaces. Dipping in halide salt solutions was examined for their inhibition of surface browning on 'Granny Smith' apple slices and the effects on biochemical factors associated with browning. RESULTS: Delay in browning by salts was greatest with chloride = phosphate > sulfate > nitrate with no difference between sodium, potassium and calcium ions. The effectiveness of sodium halides on browning was fluoride > chloride = bromide > iodide = control. Polyphenol oxidase (PPO) activity of tissue extracted from chloride- and fluoride-treated slices was not different to control but when added into the assay solution, NaF > NaCl both showed lower PPO activity at pH 3-5 compared to control buffer. The level of polyphenols in treated slices was NaF > NaCl > control. Addition of chlorogenic acid to slices enhanced browning but NaCl and NaF counteracted this effect. There was no effect of either halide salt on respiration, ethylene production, ion leakage, and antioxidant activity. CONCLUSION: Dipping apple slices in NaCl is a low cost treatment with few impediments to commercial use and could be a replacement for other anti-browning additives.

© 2015 Elsevier Ltd. Ascorbic acid and calcium ascorbate are used commercially in dip solutions to inhibit the development of browning on the surface of fresh-cut apple slices. A sodium chloride dip has also been shown to inhibit browning and this study examined its interaction with various forms of ascorbate on the postharvest life of apple slices. Comparison of the effectiveness of ascorbate moieties showed that the concentration of ascorbic acid required to achieve any desired postharvest life was twice that of calcium ascorbate, but calcium, sodium and potassium ascorbates were equally effective in inhibiting browning. The inclusion of 0.1mol/l sodium chloride into a dip requires only half the concentration of ascorbate to maintain the same postharvest life. The very low cost of sodium chloride means that materials in such a dip are about half the cost of an ascorbate-only solution. Since 0.1mol/l sodium chloride does not affect the taste of apple slices and is an allowable food additive, it should be considered as a cost effective partial replacement of ascorbate in commercial dips. There also seems to be a cost advantage of sodium ascorbate over calcium ascorbate.

To study factors influencing the development of pineapple blackheart we are undertaking functional analyses of a polyphenol oxidase promoter whose expression is induced in blackheart affected tissues. Since transgenic pineapple fruit take three years to develop, such an analysis must be undertaken using transient assays. In this report we describe experiments aimed at optimising a transient assay system using biolistic DNA delivery in pineapple fruit. Two factors are shown to be critical, namely the use of unmethylated plasmid DNAs prepared using dam E. coli host strains, and the use of an internal standard to control for the inherent variability of transient expression assays.

Thirty-one commercial valerian preparations available in Australia, including teas, tablets, capsules and liquids, were analysed by HPLC for valepotriates, valerenic acid and valerenic acid derivatives. The concentration of valerenic acid and its derivatives ranged from <0.01 to 6.32 mg/g of product. Powder capsules, on average, contained the highest concentration of valerenic acids (2.46 mg/g) and liquids the lowest concentration (0.47 mg/ml). The mean concentration of valerenic acid in the five products standardized against valerenic acid (3.56 mg/g) was significantly higher than in the 26 non-standardized products (0.89 mg/g). There was a significant relationship between valerenic acids content and added valerian root for the standardized products but not for the non-standardised products. Valepotriates were found at low levels (<1.0 mg/g) in some teas but were not detected in any of the finished products.

Changes in alkylamide and cichoric acid concentrations during the handling and storage of freshly harvested and dried Echinacea purpurea plants were investigated. Plants subjected to varying degrees of physical damage to simulate rough handling were found to show no change in the concentrations of alkylamides and cichoric acid when subsequently dried within 24 h. Storage of undamaged fresh plant material at 20 °C and 60% RH for 30 days also showed no significant loss of either group of constituents. Storage of dried crushed plant material showed that alkylamides were degraded at 20 and 30 °C, especially when held in light, but no loss occurred when stored at 5 °C in the dark. Cichoric acid was found to be stable at 5, 20 and 30 °C provided that the moisture content remained low or enzymic activity was eliminated by blanching. The findings have implications for the handling and storage of echinacea to optimise retention of alkylamides and cichoric acid. (C) 2000 Society of Chemical Industry.

An overview is given of the current position of medicinal herbs in general in relation to usage, market and production, types of pharmacological activity and how they differ from conventional drugs. The increasing importance of quality and manufactured products is also discussed. A more detailed consideration of these issues is given in relation to echinacea, valerian and St John's wort as these herbs are well studied, are market leaders and have widespread community usage.

Echinacea purpurea plants grown at two sites were analyzed for alkylamides and cichoric acid content at four growth stages from pre-flowering to senescence. Total alkylamide concentration in the root, stem and leaf decreased throughout the first growing season while the concentration in flowers increased. In mature plants, the root contained about 70 percent of the total plant alkylamides with approximately 20 percent in flower, 10 percent in stem and 1 percent in leaf tissue. The relative proportion of individual alkylamides in the root did not change during plant growth. Cichoric acid concentration in plant tissues did not change during plant growth, but did decrease during plant senescence. Similar concentrations of cichoric acid were measured in root, flower and leaf tissues, but stem levels were lower. In mature plants, the flower and leaf each contained about 35 percent of the total plant cichoric acid while the root and stem contained approximately 20 and 10 percent, respectively. © 2002 by The Haworth Press, Inc. All rights reserved.