Why do you label plates on the bottom, not on the lid? After the culture medium is set, and streaked with the required microbe/stock, the lid is put on and the petri dish is incubated upside down to minimize contamination. So, it is easier to read the label on the bottom.

Question: Why is it important to label the bottom of the agar plate (the side with the agar) and NOT the lid of the plate? If you label the lid of the plate and the lid and the bottom (agar portion) are separated you no longer know what sample is on your plate. Labeling the lid can lead to contamination of the sample.

Petri dishes are labelled on the bottom rather than on the lid. Write close to the edge of the bottom of the plate to preserve area to observe the plate after it has incubated. Labels usually include the organism name, type of agar, date, and the plater’s name or initials.

Petri dishes need to be incubated upside-down to lessen contamination risks from airborne particles landing on them and to prevent the accumulation of water condensation that could disturb or compromise a culture.

Most yeasts and molds are heat-sensitive and destroyed by heat treatments at temperatures of 140-160°F (60-71°C). Some molds make heat-resistant spores, however, and can survive heat treatments in pickled vegetable products.

120°F

between 105 and 108 F.

40° F (4° C) Used directly from the fridge, yeast is too cold to work properly.

The cold will only kill your yeast if you allow it to freeze. As long as the yeast isn’t frozen, it’s simply dormant, and can be reactivated when it is warmed up and receives adequate nutrients in the future.

At low temperature (0-10oc) yeast will not grow but die either. At temperature (100c-35c) yeast will grow and multiply faster at higher temperature with an optimal growth at (30 or 37oc) (that depends on the species). A high temperature (>50oc) the cells die.

between 90˚F-95˚F

If you have been storing your yeast in the freezer or refrigerator, take out as much as your recipe calls for and allow to sit for approximately 45 minutes to allow it to reach room temp. Yeast is a living organism. It will lose its activity over time even if you have not opened the package.

Yeast can survive freezing. You will have to bring the yeast back to room temperature without over heating them, so naturally let them warm up.

The most basic way to halt fermentation is with sulfite additions and cooling the wine down near freezing temperatures (which for a 13% ABV wine is approximately 22 °F/-6 °C) for an extended time. This addition will considerably inhibit the yeast population.

Stored in the freezer, our dry yeast will keep for months past that expiration date. Far from hurting the little yeast cells, freezing puts them in a state of suspension. Keep them in an airtight container where they are protected from oxygen and humidity. The glass jar the yeast comes in is usually just fine.