IN VITRO STUDIES TO CONTROL THE GROWTH OF MICROORGANISMS OF SPOILAGE AND SAFETY CONCERN IN HIGH‐MOISTURE, HIGH‐pH BAKERY PRODUCTS

Abstract

Initial agar plate studies were done to determine the effects of various levels (0 to 2,000 ppm) of potassium sorbate (KS) and sorbic hydroxamic acid (SHA) over a wide pH range (5 to 9) on the growth of microorganisms of spoilage and safety concern in high‐moisture, high‐pH bakery products. While growth of most microorganisms was inhibited for > 28 days on agar plates containing ∼1,000 ppm of KS at pH 5 and incubated at 30C, growth of all microorganisms occurred in plates at pH 7 and 9, regardless of the concentration of KS. SHA was equally effective at pH 5, however, it proved to be a more effective inhibitor against most microorganisms at higher pH (9). Subsequent agar plate studies were done with water‐ethanol (WE) and mastic oil‐ethanol (ME) emitters. While WE emitters failed to control the growth of all microorganisms under investigation, ME emitters controlled the growth of most microorganisms, with the exception of Listeria monocytogenes, for ∼12 to 28 days on agar plates packaged in high‐gas‐barrier Cryovac or metallized bags, respectively. Inhibition was not simply due to the levels of ethanol, which ranged from ∼1.2 to 2.8% v/v, but rather, the mastic volatiles in the package headspace. This study has demonstrated the potential of SHA and ME emitters to control the growth of several microorganisms of spoilage and safety concern in high‐moisture, high‐pH bakery products. However, the type of packaging material influenced the antimicrobial efficacy of this vapor‐phase inhibitor.

Strategies to Extend Bread and GF Bread Shelf-Life: From Sourdough to Antimicrobial Active Packaging and Nanotechnology

“…More recently, ethanol emitters have been used in combination with essential oils. Koukoutsis and colleagues (2004) [58] evaluated the water-ethanol (WE) and mastic oil-ethanol (ME) emitters to control the growth of microorganisms in high-moisture and high pH bakery products. Besides preventing or delaying bread spoilage, ethanol is effective against bread staling since it acts as a plasticizer of the protein network of the bread crumb [53].…”

“…Nanocomposites have also improved barrier ability against oxygen, carbon dioxide, ultraviolet radiation, moisture and volatiles. In addition, they may (i) let air and other enzymes out but not in, (ii) degrade ripening gas, such as ethylene, and (iii) have antimicrobial activity [56,[58][59][60][61][62][63]. Hence, nanocomposites may be used to extend food shelf-life, thus reducing the addition of man-made preservatives in foods.…”

CONTROL OF BACILLUS CEREUS IN HIGH‐pH CRUMPETS

“…A strain of B. cereus , FN 13, isolated from cereal-based products, was obtained from the Bureau of Microbial Hazards, Ottawa, ON, Canada. The inoculum and working suspensions of B. cereus (10 3 CFU/mL) were prepared as described previously by Koukoutsis et al (2004). Crumpets were inoculated, in triplicate, with appropriate amounts of the working suspension at five equidistant locations on the surface of each crumpet to give a final inoculum of ~ 10 2 CFU/g.…”

“…Furthermore, they have also been shown to have powerful antioxidant and antimicrobial properties (Abdel-Rahman and Soud 1975;Tassou and Nychas 1995;Alippi et al 1996;Iuak et al 1996;Huwez et al 1998;Magiatis et al 1999). More recently, Koukoutsis et al (2004) showed that SHA and emitters containing combinations of mastic oil and ethanol (ME) on sterile pads were both effective in controlling the growth of microorganisms of spoilage and safety concern in bakery products over a wide pH range (5-9) on agar plates. However, little is known about the ability of these two methods of preservation to control the growth of B. cereus in crumpets.…”

“…1999). More recently, Koukoutsis et al. (2004) showed that SHA and emitters containing combinations of mastic oil and ethanol (ME) on sterile pads were both effective in controlling the growth of microorganisms of spoilage and safety concern in bakery products over a wide pH range (5–9) on agar plates.…”