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The Effects of Preservatives on Rhizopus Stolonifer

Rhizopus stolonifer, more commonly known as black bread mold, is a ubiquitous organism that is commonly found on breads, fruits, vegetables and meats. The inhibition of this mold is essential to reduce losses when shipping fresh produce over long distances. Several preservatives can efficiently inhibit the growth of R. Stolonifer on foodstuffs.

  1. Efficacy of Acetic Acid

    • A study published in the November 2010 issue of the "International Journal of Pharmaceutical Sciences Review and Research" investigated the effects of preservatives on controlling the growth of Rhizopus stolonifer. The researchers evaluated acetic acid, lactic acid and citric acid against fungi isolated from bakery products and pickles. The study found that acetic acid inhibited all isolates of R. stolonifer, whereas acetic acid and lactic acid were completely ineffective.

    Methyl p-Hydroxybenzoate

    • Portuguese dry-smoked sausages are packaged to obtain a maximum shelf-life of 120 days at room temperature. An article appearing in the June 2007 issue of the "Journal of Food Protection" evaluated the susceptibility of molds isolated from dry-smoked sausages to three preservatives: potassium sorbate, sodium benzoate and methyl p-hydroxybenzoate (MHB). The study found that MHB effectively inhibited the growth of all molds tested; however, when the concentration was lowered to 0.05 percent, the inhibitory effect decreased. The study also found that potassium sorbate was more effective than sodium benzoate against toxic molds.

    Fumigation of Fruits

    • Fruit is often fumigated with preservatives to reduce decay during shipping. A study in the June 1998 issue of "Plant Disease" tested vapors of acetic, formic and propionic acids to prevent the growth of several molds, including R. stolonifer, on eight cherry, 14 pome, and three citrus fruit varieties. The researchers inoculated the fruits with fungal pathogens and allowed them to grow for 24 hours. Afterwards, the fruit were fumigated in an air-tight chamber and observed for decay. The study found that decay was reduced by 82, 90 and 94 percent by acetic, formic and propionic acids, respectively.

    Lemongrass Oil

    • Naturally occurring preservatives have been the subject of research to replace chemical additives. An article published in the June 2007 issue of "Innovative Food Science & Emerging Technology" examined the antifungal effects of lemongrass oil against five varieties of molds. The researchers found that up to 70 percent of fungal spore production was inhibited by the extract. The study concluded that lemon grass oil is an effective alternative to chemical food preservatives.

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