Melting Agar by Microwave Energy

Abstract

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.

COMPARISON OF MIKROCLAVETM STERILIZATION SYSTEM AND CONVENTIONAL AUTOCLAVING FOR THE STERILIZATION OF MICROBIOLOGICAL MEDIA 1

“…An appropriate amount of dehydrated nutrient agar (DIFCO) was distributed in 600 nil of distilled water in a 1000-ml beaker. The beaker was placed in the center of a conventional microwave oven and heated until the agar melted completely (Fung and Lin 1984). The melted medium (100 ml) was then transferred to Wheton bottles (250 ml).…”

“…The effects of microwave radiation on many microorganisms in different food systems were reviewed by Fung and Cunningham (1980). The conventional microwave oven is a convenient and efficient way of preparing agars for autoclaving or melting previously sterilized agar for plating and cultivation o f bacteria (Fung and Lin 1984;Liang and Fung 1988).…”

Performance of Some Heat-Sensitive Differential Agars Prepared and Melted by Microwave Energy

“…The microwave oven is very convenient and efficient in preparing and melting standard plate count agar compared to the conventional method (1,2,3). There is no documentation about the effect of microwave energy on heat-sensitive differential agar, such as violet red bile agar, bismuth sulfite agar, desoxycholate citrate agar, and KF Streptococcus agar.…”