Beneficial impact of exogenous arginine, cysteine and methionine on postharvest senescence of broccoli.

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.

Antifungal effect of gaseous nitric oxide on mycelium growth, sporulation and spore germination of the postharvest horticulture pathogens, Aspergillus niger, Monilinia fructicola and Penicillium italicum.

AIM: To evaluate the antifungal activity of nitric oxide (NO) against the growth of the postharvest horticulture pathogens Aspergillus niger, Monilinia fructicola and Penicillium italicum under in vitro conditions. METHODS AND RESULTS: Different volumes of NO gas were injected into the Petri dish headspace to obtain the desired concentrations of 50-500 microl l(-1). The growth of the fungi was measured for 8 days of incubation in air at 25 degrees C. All concentrations of NO were found to produce an antifungal effect on spore germination, sporulation and mycelial growth of the three fungi, with the most effective concentration for A. niger and P. italicum being 100 and 500 microl l(-1) for M. fructicola. CONCLUSIONS: Short-term exposure to a low concentration of NO gas was able to inhibit the subsequent growth of A. niger, M. fructicola and P. italicum. SIGNIFICANCE AND IMPACT OF THE STUDY: NO gas has potential use as a natural fungicide to inhibit microbial growth on postharvest fruit and vegetables.

Use of a solid mixture containing diethylenetriamine/nitric oxide (DETANO) to liberate nitric oxide gas in the presence of horticultural produce to extend postharvest life.

Postharvest treatment of fruit and vegetables with a low concentration of nitric oxide gas can extend postharvest life but application of nitric oxide by release from a gas cylinder is not feasible for many horticultural situations. This paper reports on development of a solid mixture to generate nitric oxide gas in the presence of horticultural produce. The solid NO-donor compound, diethylenetriamine/nitric oxide (DETANO) was found to quantitatively liberate nitric oxide in the presence of a range of acidic substances including citric acid. A solid mixture of DETANO and citric acid with wheat starch added as a filler and moisture absorbent in the ratio of 1:10:20 was found to be stable for at least six months when stored in dry air. However, in humid air, absorption of moisture from the atmosphere led to reaction of DETANO with citric acid and the evolution of nitric oxide gas. When the dry mixture was placed in a container with strawberry and mushroom, the moisture given off by produce activated the mixture and resulted in a similar extension in postharvest life as achieved by direct fumigation with nitric oxide gas. Commercial use of such a solid mixture could be through tablets or sachets which are more manageable in a farm or packing house than gas fumigation.

Use of ISO-NOP200 for measurement of NO in the gas phase under controlled humidity conditions.

A technique has been developed to measure nitric oxide (NO) in the gas phase using the ISO-NOP200 NO-specific probe, which was designed to only measure NO in solution. It was found that probe output was responsive to the relative humidity (RH) of the atmosphere. Increasing sensitivity of probe output to NO was observed with increasing RH but the time to achieve a stable output was also increased. The recommended method to give high sensitivity but an acceptable time between analyses was to hold the probe at a constant temperature (20 degrees C) in a sealed 20 ml glass vial containing 4 ml of a saturated solution of NaCl, which provides a constant RH of 75%. NO standards and samples were injected directly into the vial and provided good baseline stability and a limit of detection of 0.18 microl/L in the vial. The limit of detection of the analytical sample will depend on the volume of gas injected into the vial. Up to 4 ml could be injected without disturbing probe stability and this equates to a detection limit of 0.75 microl/L NO. However, analysis of the internal atmosphere of banana fruit could only consistently extract 1 ml of gas, which gave a detection limit of 3 microl/L NO.

Valepotriates and valerenic acids in commercial preparations of valerian available in Australia.

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.

Herbal products: active constituents, modes of action and quality control.

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.

Influence of multi-holed shakers on salting on food.

In a study of 2241 Australian adults consuming main meals at a cafeteria, single-and multi-holed (5, 9, 13) salt shakers were weighed before and after use. For all hole numbers, salt use increased linearly with an increase in hole area to a maximum value of 1.1-1.2 g which was the same irrespective of hole number. For a given hole area multi-holed shakers decreased salt use compared with single-holed shakers suggesting that multi-holed shakers are easier for consumers to control. However the greatest restriction in salt use (0.37 g per meal) is obtained by use of a single-holed shaker of 3 mm2 hole area.

Contributions of foods to sodium in the Australian food supply.

The sodium contributions of various foods in the Australian supply have been calculated by applying recent local food composition data to food availability data and to typical notional Australian diets. Sodium available for consumption from the food supply was 3.00 g per capita per day. Of foods which are salted during processing, the three heaviest contributors of sodium were bread (23 per cent of total available sodium), processed meat and fish (14 per cent), and margarine (8 per cent). Other important contributors were breakfast cereals, biscuits, cheese, butter, potato crisps, dried soups and cakes (including pastries, pies and puddings). Foods identified by health authorities as 'highly salted' and thus prime targets for reduced consumption, provided 33 per cent of total available sodium, less than the 50 per cent contributed by other foods salted during processing. Take-away foods per se did not contribute more sodium than processed foods generally.

Salting of take-away foods at point of purchase.

Sodium and potassium levels were determined in ten types of fried take-away foods and sandwiches purchased from retail outlets with and without the addition of salt by the food handler. In virtually all foods the major source of sodium was that added during manufacture of the food ingredients rather than that added by the food preparer.

Sodium and potassium contents of salts, salt substitutes, and other seasonings.

Samples of table, cooking, rock and sea salts, flavoured salts, salt substitutes, seasonings, and monosodium glutamates were analysed for sodium and potassium content. The average sodium content of table, cooking and rock salts was about 16 600 mmol/kg, and that of sea salt was only marginally lower at about 16 100 mmol/kg. Flavoured salts contained about 11 900 mmol/kg, while "low salt" products contained about 9400 mmol/kg. Products marketed as containing "no salt" contained less than 20 mmol/kg (equivalent to less than 0.1 g sodium chloride per 100 g); all other salts contained the equivalent of over 50% sodium chloride. Nomenclature of seasonings was no indication of the sodium content, which ranged from 1060 to 12 960 mmol/kg. The monosodium glutamates contained 5300 mmol sodium per kg. Potassium was present at nutritionally significant levels only in "no salt" (12 800 mmol/kg) and "low salt" products (5300 mmol/kg).

Liquid chromatography, microfluorometry, and dye-titration determination of vitamin C in fresh fruit and vegetables.

The vitamin C content of several fresh fruit and vegetables was determined by a liquid chromatographic (LC) method which gave simultaneous separate values for ascorbic acid and dehydroascorbic acid (DHA) and by the official AOAC methods of microfluorometry and dye-titration. The levels of ascorbic acid obtained by LC and dye-titration were in good agreement, except for a few colored products where it was difficult to determine the end point of the titration. The combined values for ascorbic acid and DHA obtained by LC and microfluorometry were in agreement for most produce, but for about one-third of the samples, the values obtained by microfluorometry were significantly higher.

Salting of food--a function of hole size and location of shakers.

The establishment of an association between hypertension and the level of sodium in the diet has focused interest in many countries on the amount of salt added to food, with estimates of intake in western countries being in the range 6-14 g per person per day. As a result, many health authorities have advocated a decrease in salt consumption by the population in general, a common suggestion for achieving a meaningful reduction being to limit the amount of salt used at the table. It is generally assumed that salting habits are influenced by taste preference as shaped by socio-cultural determinants. However, from our observations of the rate of discretionary salt usage of over 1,900 people (mainly adults) consuming main meals in public institutions in Sydney, Australia, were suggest that salting is strongly influenced by the physical factor of mode of presentation of salt to the consumer, particularly the hole size of the salt shaker, and is not influenced by demographic variables.

Sodium and potassium levels in Australian processed foods.

We analysed 118 foods available in retail outlets in Sydney for their sodium and potassium content. The concentration of sodium in the types of food examined was (from highest to lowest); salami, ham, luncheon meat, corned beef, liverwurst, breakfast cereals, cracker biscuits, frankfurters, cheese, crispbread, bread, sweet biscuits, canned vegetables, cheesecake and frozen vegetables. There were large variations within some of these groups, especially cheese and breakfast cereals. We have summarized data recently published on 250 other foods. The concentration of potassium was highest in bran-based breakfast cereals and lowest in cheese.

Analysis of water soluble vitamins by high pressure liquid chromatography.

Resolution of the water-soluble vitamins--pyridoxin, riboflavin, niacinamide, vitamin B12, thiamin, ascorbic acid, niacin and folic acid--by high pressure liquid chromatography was examined on two bonded-phase columns, muBondapak C18 and muBondapak NH2. The effect on the retention times of individual vitamins and the separation of a multivitamin sample was determined using varying proportions of water/methanol as the eluting solvent and by addition of various salts, buffer solutions and PIC reagents to the water/methanol. Each vitamin was able to be eluted satisfactorily from muBondapak C18. It was found that seven vitamins could be resolved from a multivitamin mixture in a single analysis in several solvent systems with the total time for the analyses being always less than 40 min. With muBondapak NH2, all the vitamins except folic acid were eluted and six vitamins could be resolved from a mixture in a single analysis. The speed of analysis was greater with muBondapak NH2 with all compounds eluted in 15 min and the peaks were sharper. The order of elution was essentially the reverse of that obtained with muBondapak C18.