Yogurt ppt

Our Class2AOCB I.P.S.I.A San Benedetto del Tronto

Starting from fresh non pasteurized milk we prepared homemade yoghurt using

commercial yoghurt as a starter (sample B)

and lyophilized enzymes (sample C).

Fresh milk

Heating 60°C

Cooling at 45°C

Aliquot 1 Aliquot 2White whole commercial yoghurt

Lyophilized milkenzymes

Sample B Sample C

Sample A

Incubation at 37°C 24 h Incubation

at 37°C 24 h

HO

OH

H

HO

H

H

OHH

OH

O

OH

H

HO

H

HOH

H

OH

HO

CH3

COOH

C

OHH

• What happens when Streptococcus thermophilus and Lactobacillus bulgaricus are put into the milk?

They transforme lactose into lactic acid

• To 50 ml of milk or yoghurt we add 3-4 drops of phenolphthalein, titrated by NaOH 0,25 N.

• The acidity degree, expressed in Soxlet Hankel degree, derives from the mls of NaOH needed to titrate 100 ml of milk.

Fresh Milk Yogurt (sample B and C)

ml NaOH 4

S.H degree = 8

ml NaOH 46

SH degree = 92

•The taste of a yoghurt depends not only on organoleptic aspects but also on the number of lactic enzymes contained.•We compared the quantity of these enzymes in sample A (commercial yoghurt), Sample B (yoghurt prepared with commercial yoghurt), Sample C (yoghurt prepared with lyophilized lactic enzymes)•The different samples have been inoculated with on Rogosa Agar and incubated for 48h at 37°C and observed soon after prepared, after 5 days, and after 10 days.

Sample C at different dilutions after 10 days.

Sample C at different dilutions

Sample A: no growth!!!

Note the difference between A and C

Sample c

Just open 48.000.000 ufc/ml

After 5 days 26000 ufc/ml

After 10 days

0 ufc/ml

* N.B. used 10 days before the expiring date.

B With commercial

yoghurt

Cprepared

With lyophilized enzymes

Just prepared 17.100.000 ufc/ml 114.000.000 ufc/ml

After 5 days 215.000 ufc/ml 1.208.000. ufc/ml

After 10 days 120.000 ufc/ml 812.000 ufc/ml

• With 1 l of milk we can make 7 yoghurt pots, using both commercial yoghurt and lyophilized enzymes

B CMilk price 1 € 1 €Starter price from 0,65 to 1 € 1 €Price of a single pot of yoghurt (about 125 grams)

from 0,235 € to 0,285 €

0,285 €

• If we don’t buy plastic bottled milk but we use milk directly bought from the vending machines, using only glass bottles (that we can use thousands times), then we put our yoghurt in glass jars (that we can use again and again) we avoid to carry aluminium and plastic to the rubbish tip.

• If, for example we use 1 yoghurt pot per person, per day, we could easily know the quantities of plastic and aluminium saved in a year time.

Aluminium per year per person

Plastic per year per person

17,15 grams 3,6 kg

Grams of aluminium

Grams of pot

Gramsbottle

0,49 5,98 27,5