use of biological resources

Question 1

what kingdom is yeast found in?

Answer 1

fungi -unicellular

Question 2

what are yeasts two main industrial uses in food?

Answer 2

bread and beer

Question 3

what type of respiration is used in bread making and what is the equation?

Answer 3

anaerobic
glucose->ethanol + carbon dioxide

Question 4

explain yeats use within bread?

Answer 4

-produces carbon dioxide which bubbles and expands the dough and helps the bread rise
-the high temperatures used in bread making mean that ethanol does not remain in the bread after cooking
-yeast respires using the glucose from the sugar (starch converts to sugar) in the dough

Question 5

describe the anaerobic experiment for yeast?

Answer 5

-dissolve sugar previously boiled mixture

-add yeast and form a suspension, and pour into boiling tube

-add a layer of oil on top to keep oxygen out to make it anaerobic

-connect a measuring cylinder, containing water/lime water

-turn the measuring cylinder upside down in a water trough to measure volume of CO2 gas

-place yeast tube in a water bath at desired temperatures (10,20,30 etc)
-find difference in volume of CO2
-find optimum temp

Question 6

what bacteria is used in yoghurt making?

Answer 6

lactobacillus

Question 7

what is step 1 of yoghurt making?

Answer 7

milk is pasteurised to 85* or 95* to kill an unwanted micro-organisms that may turn it into curds and whey

Question 8

what is step 2 of yoghurt making?

Answer 8

milk is homogenised to disperse any fat globules

Question 9

what is step 3 of yoghurt making?

Answer 9

milk is cooled to 40* so it can be inoculated with the starter of lactobacillus without it being denatured

Question 10

what is step 4 of yoghurt making?

Answer 10

the culture is incubates to 40/45* for several hours to allow lactobacillus to digest milk proteins and ferment to lactose and lactic acid

Question 11

what is step 5 of yoghurt making?

Answer 11

the yoghurt mix becomes thick as the bacteria has digested the lactose forming lactic acid, the pH becomes acidic making the milk proteins coagulate (set)

Question 12

what is the final step of yoghurt making?

Answer 12

the yoghurt is stirred and cooled to 5* to a smooth consistency and so that the flavourings and fruit can be added without excessive warmth marring their flavour.