The behavior of Listeria monocytogenes was evaluated during storage of a queso blanco type of cheese produced with acidulants (citric, malic, or acetic acids) and a commercial lactic acid bacterium fermentation product, ALTA™2341 (ALTA). The cheese was prepared by direct acidification (final pH 5.2), with and without 0.6% ALTA, inoculated with 106 CFU/g of L. monocytogenes, and stored at 4 or 20°C for 42 and 7 days, respectively. Levels of L. monocytogenes increased in cheese coagulated with citric or malic acids and stored at 4°C, but decreased slightly in cheese coagulated with acetic acid. At 20°C, counts of L. monocytogenes increased in cheeses acidified with citric or malic acid, but counts did not increase appreciably in cheese acidified with acetic acid. When cheese was stored at 4°C, the presence of 0.6% ALTA resulted in lower counts of L. monocytogenes compared with counts in cheese that did not contain ALTA. However, at 20°C populations of L. monocytogenes increased in cheese containing ALTA regardless of acid type. Additional studies compared the effects of acetic acid, alone or in combination with 0.6 or 2.5% ALTA, against low (102 CFU/g) and high (106 CFU/g) inoculum levels. When inoculum levels were low, pathogen counts decreased by > 1.1 log10 CFU/g in all formulations at 4°C. After 7 days at 20°C, pathogen counts increased in the queso blanco type of cheese prepared with acetic acid alone. In contrast, in the presence of 0.6 or 2.5% ALTA, 7-day counts were less than the initial inoculum. With high inoculum levels at 4°C, counts of L. monocytogenes were less than the initial inoculum in the acetic acid-coagulated queso blanco type of cheese with or without ALTA. At 20°C, counts increased in the queso blanco type of cheese prepared with 0.6% ALTA, but decreased appreciably in cheese prepared with 2.5% ALTA. These results demonstrate that acetic acid is significantly more effective than malic or citric acids for controlling L. monocytogenes in queso blanco, and that inclusion of ALTA can provide added protection against the pathogen.

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β-Carotene is the most treasured provitamin A carotenoid molecule exhibiting antioxidant and coloring properties and significant applications in the food, pharmaceutical, and nutraceutical industries. β-Carotene has many biological functions within the human body; however, it is not synthesized within the human body, so its requirements are fulfilled through food and pharmaceuticals. Its manufacturing via chemical synthesis or extraction from plants offers low yields with excessive manufacturing expenses, which attracted the researchers toward microbial production of β-carotene. This alternative provides higher yield and low expenses and thus is more economical. Phaffia rhodozyma is a basidiomycetous yeast that is utilized to prevent cardiovascular diseases and cancer and to enhance immunity and antiaging in people. This paper reviews the methods of production of β-carotene, biosynthesis of β-carotene fromP. rhodozyma, factors affecting β-carotene production during fermentation, and pharmacological properties of β-carotene.