Antioxidants belong to a class of compounds used to retard oxidation of chemicals in foods. These compounds, such as BHA, BHT, TBHQ, PG, etc. are approved to be used in foods by government agencies. In the past 10 years considerable interest has been directed to the antimicrobial properties of these compounds due to the observations by various scientists that many of these compounds can suppress the growth of viruses, protozoa, bacteria, yeast, and molds and their subsequent production of toxic materials in foods. Thus, the dual purpose usage of these compounds (i.e., antioxidation and antimicrobial) has been the subject of many research papers. This review is designed to summarize major publications on this subject as well as present some detailed studies on the effect of major antioxidants on bacteria and mold generated in the laboratory of the author in recent years.

The antifungal effect of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary butylhydroquinone (TBHQ) and propyl gallate (PC) alone or in combination on three toxigenic strains of aspergiIIi (NRRL 2999, NRRL 4123, NRRL 5835) and three nontoxigenic strains of aspergilli (NRRL 5521, NRRL 5917, NRRL 5918) was examined in a solid medium and in salami. BHT and PG (0.001,0.005,0.01,0.02g per plate) did not inhibit growth, sporulation, and toxigenesis of ail six cultures. Aflatoxin production by toxigenic aspergilli (Bi, B2, Gr and G2) in the presence of BHA, TBHQ, and a combination of BHA and TBHQ was reduced significantly (P < 0.05). In salami BHA, TBHQ alone or in combination at 100 ppm significantly (P < 0.05) decreased the aflatoxin production by aspergilli when compared to control samples. A combination of BHA and TBHQ showed synergistic inhibition in both studies (solid medium and salami studies).

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Enumeration of yeast and molds on trypan blue (at 1:10 000 dilution) in potato dextrose sugar (trypan blue agar) was compared with potato dextrose agar (PDA) plus safranin flooding procedure using the hydrophobic grid-membrane filter technique (HGMF) of the ISO-GRID system. Yeast and mold grew well on trypan blue agar, producing easily recognized blue colonies on the ISO-GRID system. Results indicated that trypan blue agar is more convenient to use than the PDA plus safranin flooding procedure and as reliable (r = 0.99) for enumerating yeast and mold of cheeses, spices and dry products, and salad samples.

The microwave oven is very convenient for melting agar for viable cell counts. Composite data of four microwave ovens indicated that melting time for 50 ml of agar per bottle was about 1 min for one bottle, 1.5 min for two bottles, and 2.5 min for four bottles heated simultaneously. Melting time for 100 ml of agar per bottle was about 1.5 min for one bottle, 2.5 min for two bottles, and 4 min for four bottles. Melting times of agar in square or flat bottles were similar. Agar melted by microwave treatment performed in viable cell counts equally as well as agar melted by the conventional boiling method. Even after prolonged (50% longer than melting time) microwave treatment, performance of the agar remained unchanged. Agar melted by microwave treatment can remain in liquid form (48°C) in situ for about 30 min (50 ml) and 1 h (100 ml). When removed from the microwave oven immediately after melting, the agar remained in liquid form (48°C) at room temperature for about 25 min (50 ml) and 40 min (100 ml). The microwave oven is highly efficient in melting agar without detrimental effects on the performance of agar.