Sunday, June 17, 2007

How Ethylene Gas Affects Produce

Townsend Letter for Doctors & Patients - October 2005

Following harvest, apple produce commences to release ripening-hormone ethylene gas. Over-ripening reduces the shelf life of apples, and so the reduction of ethylene is necessary. Ethylene gas removers include potassium permanganate (KMnO4), zeolite, clay, bentolite, alumino-silicate and active carbon. Other sources of ethylene include ripening fruit, rotting vegetation, exhaust from internal combustion engines/heaters, smoke (including cigarettes), welding, and natural gas leaks (Han JH, 2003).

As fruit ripens, the fluid-juice within the fruit body supports aerobic bacteria and yeast/mold proliferation. Food-borne illnesses may occur due to incidental consumption of commercial, nonpasteurized ("fresh" or "unpasteurized") fruit juices (Matthys AW). Nonpasteurized fruit juice has been associated with numerous food-borne illness outbreaks since the 1920s. Disease syndromes have included salmonellosis, typhoid fever, cryptosporidiosis, Escherichia coli-related diarrhea, and hemolytic uremia (Parish 1997).

Spoilage from Aerobic Bacterial Growth in Refrigerated Apples
Whole fruit or fruit juice may be the source of food-borne illnesses due to pre-harvest contamination or consumer-neglect from too long storage. Fresh apples and unpasteurized apple juice receive little to no antimicrobial treatment and, despite their health-promoting image, may transmit or harbor dangerous contaminants. Acid fruit juices below pH 4.6 were once deemed a minor health threat due to their high acidity. Furthermore, refrigeration temperatures (below 5ºC) were thought to resist pathogen growth, until the discovery that Listeria monocytogenes can grow in temperatures as low as 2ºC. Juice spoilage typically occurs as a reflection of the indigenous microflora, yeast, mold and/or lactic acid bacteria growth. Nonetheless, the emergence of hitherto unsuspected food pathogens with acid resistance combined with an increase in susceptible individuals, immunocompromised, chronically ill, the very young and very elderly, has dramatically changed this picture. Safety must always take precedent with strict limits on production, harvest, transportation, storage, manufacture, processing, labeling and distribution. These are incorporated into Good Agricultural Practices (GAPs) and Good Manufacturing Practices (GMPs) with Hazard Analysis and Critical Control Point (HACCP) procedures being applied throughout the food chain. These will be emphasized as appropriate.

The National Food Processors Association (NFPA) has considered several options including current Good Manufacturing Practice (GMP) regulations. One of NFPA's officers wrote, "The only means of assuring that juice did not contain potentially pathogenic microorganisms was to include a microbial control step that has been scientifically proven to be effective in providing a level of protection equivalent to pasteurization in the process. Two percent of all juice products are not pasteurized or otherwise treated. Illness attributable to raw juice or juice includes imported frozen raw (unpasteurized) Mamey puree (13 cases, typhoid fever—Salmonella), raw apple juice in Canada (E. coli 0157:H7), raw orange juice in Australia (435 cases—Salmonella), raw orange juice from Arizona (300 cases—Salmonella muenchen in 20 states) and raw apple juice in Tulsa, Oklahoma (9 cases—E. coli 0157:H7). Only a microbial kill step applied to harvested raw fruit and/or juice itself can ensure that potentially pathogenic microorganisms are eliminated. Sorting and washing of fruit should be standard practice in all Good Manufacturing Practice operations for juice production but cannot be relied upon to ensure the complete removal of pathogenic microorganisms.

While theoretically possible, achieving an appropriate level of protection from pathogenic microorganisms without applying some inactivating treatment to the juice seems technologically infeasible at this time. Processing methods that may provide an equivalent kill step include batch and continuous high-pressure processing systems, pulsed electric fields, ultraviolet light, electron beam treatment, irradiation, ultra filtration, or use of one or more of the preceding treatments in combination with an anti-microbial compound" (Matthys AW).

Potassium permanganate (KMnO4) is a potent antimicrobial compound, which acts as an oxidizing agent directly reducing the contaminated environment of indigenous toxic substances and/or aerobic bacteria. KMnO4 is so potent that it should not come in direct contact with humans or food nutrients.

Pulsed Ultra Violet-Light Decontamination of Small Fruits
Each year the United States looses over one billion dollars due to foodborne illnesses. It is estimated that there are 76 million illnesses each year with fresh produce being the second most common cause. Between 1990 and 2003 there were 23,857 cases of foodborne illness traced back to fresh produce. Small fruits, such as raspberries and strawberries, have been implicated in numerous cases of foodborne illness. At least five outbreaks of Cyclospora cayetanensis were traced to raspberries and strawberries have been implicated in three outbreaks of Hepatitis A. While there have been no recorded bacterial outbreaks associated with small fruits, the possibility exists, since the contamination routes responsible for previous outbreaks are the same for bacterial pathogens. A United States Food and Drug Administration (FDA) survey found that 1 out of 143 imported strawberry samples tested positive for Salmonella. Also, research has shown that both Salmonella and E. coli O157:H7 are capable of surviving on fresh strawberries for over 7 days. Currently raspberries and other small fruits are not washed prior to market and research has shown that washing with water or other common sanitizers is not enough to combat this potential contamination problems. Pulsed UV-light is one technology. In this study pulsed UV-light was applied to strawberries and raspberries at varying distances and times. Maximum reductions of 99.99% and 99.98% of E. coli O157:H7 and Salmonella were obtained on raspberries and 99.29% and 99.49% on strawberries. This research indicates that treatment with pulsed UV-light shows promise for the decontamination of small fruits.

In relation to contamination of soft fruit, it used to be that fruit pickers urinated into the baskets of fruit to increase the weight (with regard to payment for their work), and that some fruit pickers would urinate into the fruit as a way of hitting back at their employers etc. However, the same difficulties apply to any area of agricultural food production where basic levels of hygene canot be guaranteed.

Fruit Hygene PDF