What is the purpose of using an agar slant?
Slanting the surface of the agar gives the bacteria a greater surface area on which to grow in a test tube. Furthermore, slants are created in test tubes that can be capped, which minimizes water loss. This is important because of the high moisture content of agar media.
How should the condenser and diaphragm be adjusted for optimum viewing?
How should the condenser and diaphragm be adjusted for optimum viewing? Condenser is kept at highest point, just below stage. Diaphragm varies based on how much light is needed.
Why must Agar be cooled to 50 degrees?
The sterile agar is then allowed to cool to 50 °C: this is just above the setting point of agar and pouring at this cooler temperature helps prevent condensation forming on the lid. The number of plates to be poured are placed on the bench, with their lids still on.
What is the importance of generating isolated bacterial colonies on a solid media plate?
What is the importance of generating isolated bacterial colonies? To be sure that only one cell is being examined and that it is a pure culture.
Why is sugar or salt added to foods to preserve them?
There are several ways in which salt and sugar inhibit microbial growth. The most notable is simple osmosis, or dehydration. Salt or sugar, whether in solid or aqueous form, attempts to reach equilibrium with the salt or sugar content of the food product with which it is in contact.
Does sugar preserve food?
Sugar helps preserve the color, texture and flavor of the food. The sugar in jams and jellies helps the gel to form, and increases the flavor. When large amounts of sugar are used in a recipe, the sugar also acts as a preservative by inhibiting microbial activity; thus, recipes should not be modified or adapted.
What is the best temperature range to store food that is to be reheated?
The State Sanitary Code now requires that the entire mass of all cooked and refrigerated potentially hazardous food which is to be reheated must be reheated to 165 degrees Fahrenheit or above within two hours, and held above 140 degrees Fahrenheit until served.
Is Vinegar a good preservative?
Vinegar is made from fermentation of sugar and water solutions and it acts as an effective natural preservative. The acetic acid present in vinegar kills microbes and inhibits food spoilage. Adding common vinegar in your food can not only preserve foods but also help enhance their taste.
Can you preserve fruit without sugar?
Sugar is not needed to prevent spoilage. All fruits can be safely canned or frozen without sugar. Some low- and no-sugar foods can be canned at home with very good results.
Can you preserve plums without sugar?
All fruits may be frozen without added sugar. Sugar is not needed for the preservation of frozen fruits, but it does help the fruit maintain quality longer.
Can I use Stevia instead of sugar for canning?
Canning with Stevia Stevia provides sweetness but does not provide the firm texture of sugar. Stevia can only be used in jams and jellies when used with no-sugar needed pectin—low methoxyl pectin.
Why do you add lemon juice to jam?
When you prep a big batch of jam, you begin by cutting the fruit and heating it with some sugar. The lemon juice lowers the pH of the jam mixture, which also neutralizes those negative charges on the strands of pectin, so they can now assemble into a network that will “set” your jam.
Which fruit is not suitable for jam making?
Fresh Fruit The best quality fruit will give you the best jams and jellies. Strawberries from California, peaches and plums from Argentina or Chile may look attractive, however, they are often hard, dry and low in acid and will therefore not make good jam.
Does lemon juice set jam?
To set, jam needs the right balance of acid and pectin. If you’re using low-acid fruits, such as rhubarb, apricots, peaches and strawberries, you need to add lemon juice. A handy trick to help it set is to cook jam with a muslin puch full of pectin-rich lemon rind and seeds.
Will my jam thicken as it cools?
See, the truth is that the pectin web doesn’t really solidify until everything cools down. That means it’s tricky to tell whether you’ve achieved the gel point while the action is still hot and heavy. Enter the spoon: Before you start your jam, set a plate with a few metal spoons in the freezer.
Why does my jam not set?
The other main reason for jam not setting is that it wasn’t boiled for long enough once the sugar has dissolved, so did not reach setting point. Setting point is when the boiling mixture reaches 105c/220F and a sugar/jam/candy thermometer is useful as you can put it in the pan of bubbling jam and check the temperature.
Can you Reboil jam if it doesn’t set?
Give the jam 24-48 hours to set up (because truly, sometimes it can take that long for pectin to reach the finished set). If it still hasn’t set, it’s time to determine how much jam needs to be recooked. Place the pot on the stove over high heat and bring the jam to a boil.
How do you fix jam that has set too hard?
Stiff jams or jellies can be thinned with water or fruit juice. They may or may not form a gel again once they are re-heated, as over-cooking of pectin can reduce or destroy its ability to form the gel structure.
What happens if you cook jam too long?
Cook until tender – any longer and the fruit will lose its shape. No sugar is added at this stage because a high sugar concentration can cause water to be removed through osmosis and result in hard, unappetising fruit.
Can you melt jam and reset it?
Yes it will. I’m pretty sure it will. I remember my mum used to melt down apricot jam with a little water & then sieve it to make an apricot glaze for cakes – any leftovers re-set and just went on toast the next morning.
Can you fix overcooked jam?
Salvaging Overcooked Jam. Heat small amounts of jam in the microwave, a few seconds at a time, and then use as you would normally. If it’s still too thick, add some water while heating in the microwave, and then use it as an unusual pancake or ice cream syrup.
How long should you boil jam for?
Bring the fruit mixture to a rapid, rolling boil (when the bubbles cannot be calmed down by stirring with a spoon). Cook for 3-5 minutes until the jam reaches setting point. As your jam approaches setting point, it will thicken and start to boil more slowly, with thicker, heavier bubbles.
Why is my homemade jam so thick?
Why is my jam too thick? Fruits that are high in pectin such as apple, citrus fruits and pear will produce thick jams. The standard ratio in jam is equal measures of sugar to fruit. However, you may notice in recipes for jams made using high pectin fruits contain more sugar.
How long can homemade jam last?