1

EGYPT (5.000 YEARS AGO)Reaping in ancient Egypt. Bread is also found in tombs. Use of dough made the previous day = natural leaven

YEASTBeer and whisky processing residue – maybe invented by the Gauls

PURE CULTURE YEASTSaccharomyces cerevisiae – compressed or cream yeast.

EVOLUTION OF LEAVENING

ISRAEL (23.000 YEARS AGO)Evidence of wheat grinding kmowledge found at Ohalo IIProf. Ehud Weiss, Nature 2004

2

BIOLOGICAL LEAVENING (both production and retention of gas are important)

- compressed yeast- leaven

CHEMICAL LEAVENING

reaction between salts(acid salts+bicarbonate)

- decomposition (ammonium bicarbonate)

LEAVENING IN PHYSICS- air absorption (often with the help of eggs or emulsifyers)(ex. meringues, battered pastries, sponge cakes )

STEAM LEAVENING-puff pastry (the numerous layers of fat form a barrier against

steam)- cream puff

MIXED SYSTEMS (biological + lamination with fat)- danish pastry

LEAVENING

3

ITALIAN LAW Decree n. 502 of November 30, 1998

Art. 8 1. The yeast suitable for bread-making must be composed of (mostly)alive cells with adequate fermentative power, humidity not higher than 75% and ashes not higher than 8%of dry matter 2. The yeast cream suitable for bread-making must be composed of (mostly) alive cells with adequate fermentative power , humidity not higher than 80% and ashes not higher than 8% of dry matter.I

4

WHAT ARE WE TALKING ABOUT?

YEAST: LIVING CELLS, MAINLY SACCHAROMYCES CEREVISIAE, EMPLOYED IN BREAD-MAKING AS COMPRESSED YEAST.

NATURAL OR ACID LEAVEN: FROM SPONTANEOUS LEAVENING OF A DOUGH OF SOFT WHEA T (OR OTHER CEREALS ), USUALLY DERIVED FROM PREVIOUS SESSIONS OF BREAD-MAKING IN ORDER TO HAVE AT THE SAME TIME A DOUBLE BLASTOMYCES MICROFLORA AND BACTERIA, MAINLY LACTOBACILLUS.

MICRO-FLORA OF NATURAL LEAVEN : DERIVES FROM AN ENVIRONMENTAL CONTAMINATION OF RAW MATERIAL. THE WORKING CONDITIONS INSTEAD ALLOW THE DEVELOPMENT OF PARTICULAR MICRO-ORGANISMS AND PERMIT TO MAINTAIN THE MICRO-FLORA WHICH, IN ANY CASE, IS NOT CONSTANT. THE SPECIES DEPEND ALSO ON THEIR CAPACITY TO COHABIT (TOLERANCE TO ORGANIC ACIDS AND TO ANTIBIOTICS PRODUCED BY LACTICS AND USE OF CARBON SOURCES).

5

FERMENTATION

(absence of oxyigen)

SACCHAROSE GLUCOSE

PIRUVATE

C02

ETHYL ALCOHOL

ENERGY BALANCE

2 ATP (2x7 = 14 Kcal)

ENERGY

C6H12O6 2CO2 + 2C2H5OH + Qkcal

LEAVEN ENERGY METABOLISM

RESPIRATION

(presence of oxygen)

CYCLE OF TRICARBOSSILIC

ACIDS

C02

2H+

0=

ENERGY

H20

RESPIRATION CHAIN

OXYGEN

ENERGY BALANCE

2 + 36 ATP (38 x 7 = 266 Kcal)

C6H2O6 + 6O2 6H2O+ 6CO2 + Qkcal

NB –INSIDE A DOUGH RESPIRATION CHANGES TO FERMENTATION IN A FEW SECONDS. IN ANAEROBIOSIS S.CEREVISIAE FERMENTS, I.E. TRASFORMS SACCAROSE INTO CARBON DIOXIDE AND ALCOHOL, BUT IT CAN’T MULTIPLY.

6

GASES INVOLVED IN LEAVENING

CO2 - fermentation - carbon dioxide is highly soluble in water - bicarbonates (Na)

AIR - kneading -low water-solubility of nitrogen, which remains after the process since the oxygen is consumed by the yeast

NH3 - ammonium -it doesn’t leave salt residues;

bicarbonate it is used in low humidity final products

STEAM - formed by water - limited effect due to the high boiling

temperature

ETHANOL - from yeast fermentation - highly water-soluble, makes evaporate EXHAUST l’azeotrope (78°C)

GAS ORIGIN OBSERVATIONS

7

LEAVENING TEXTURES

BIOLOGICAL LEAVENING - compressed yeast

CHEMICAL LEAVENING- chemical yeast

STEAM LEAVENING- puff pastry

8

FORM PRESERVATION PRESERVATION ADDED CONVERSION FACTOR TEMPERATURE TIME % HUMIDITY METHOD

fresh, compressed 2 - 7°C 3 - 4 weeks 67-72 add to other ingredients or 1( 0,5 kg and 20kg wash away before kneading in acqua prima dellopackages)

fresh, crem 1 - 4°C 10 - 14 days 80 add to other 1,5(semi-liquid) ingredients

(decree 30.11.98)

dry, active room 3 - 12 months 6 - 8 hydrate at 30-43°C 0,4-0,5 temperature for 10-15 minutes before use

dry, instant room temp. 6 -12 months 4 - 6 mix with dry ingredients 0,3-0,4 in modified atm.

( pizza kits)

YEAST

9

LEAVEN

SPONTANEOUSLY LEAVENED DOUGH

OR

ACID DOUGH

OR

NATURAL LEAVEN

=

From: R. Foschino, A.Galli, 1997

“obtained by spontaneous fermentation of a dough made with water and wheat, rye, oat…”

10

• POWDERED ACID DOUGHS ARE ON SALE, WITH THE CHARACTERISTICS OF LEAVEN

• THEY ARE MAINLY USED FOR WHEAT OR RYE ACID BREAD (RATIO: 1-2% OF THE FLOUR)

• OBTAINED WITH THREE-KNEADING FERMENTATION FOLLOWED BY DRYING

• THESE PRODUCTS DIFFER IN pH (3,2 - 4,0 ) AND ACIDITY

• EMPLOYED IN BIOLOGIC BREAD MAKING BECAUSE THErE CAN’T BE USED AMELIORATORS

ACID DOUGH

11

DIFFERENT EMPLOYMENTS OF LEAVEN BASICALLY, THERE ARE FOUR TYPES OF EMPLOYMENT OF LEAVEN

TRADITIONAL METHOD OF RYE BREAD MAKING, USED IN EASTERN EUROPE AND IN GERMANY. ESSENTIAL TO REDUCE THE ACTION OF AMYLASES PRESENT IN RYE COUNTRY LEAVEN EMPLOYED FOR RURAL BREAD , MAINLY USED IN FRANCE, SPAIN, PORTUGAL AND GREECE. SAN FRANCISCO ACID BREAD, USED IN CALIFORNIA TO MAKE AN ACID AND SOFT BREAD TYPICAL OF THE AREA. FESTIVITY BREADS (PANETTONE, PANDORO, EASTER DOVES) IN ITALY

IF THE FOUR METHODS ARE SLIGHTLY DIFFERENT, THE FUNDAMENTAL PROCEDURE IS THE SAME:

MAKE A FERMENTED DOUGH WHICH ACTS AS LEAVENING AGENT IN THE PROCESS.

12

FUNCTIONS OF LEAVEN

PRIMARY FUNCTION: LEAVENING OF THE PRODUCT THROUGH THE FORMATION OFCARBON DIOXIDE AND ALCOHOL ( 1 glucose = 2 ethanol + 2 CO2) WHICH, MAINLYWHILE BAKING, TEND TO INCREASE THE VOLUME OF THE PRODUCT.

OTHER FUNCTIONS: THE BACTERIA (LACTOBACYLLUS, LATTOBACILLI, MA ANCHE PEDIOCOCCHIS, ENTEROCOCCHIS AND LEUCONOSTOC), PRODUCE

ORGANIC ACIDS, AROMATIC SUBSTANCES, CO2 (50% OF TOTAL CO2) AND ENZYMES WHICH AFFECT

• REDUCTION OF COOLING SPEED, ALSO WIT THE PRODUCTION OF ETERO-ESO-POLYSACCHARIDES (GLUCANS ex.dextrans, OLIGOFRUCTANS ex inulin) • FRAGRANCE

COMPLEX EVOLVING BIOLOGICAL SYSTEM

13

LACTIC BACTERIA

Acidifying (lactic acid, acetic acid)

Selection of microflora

• Acts on amylase and protease

• Improves the reologycal properties

• It gives the capacity of binding the water

• Improves preservability (slow staling, antimicrobic action)

Proteasic and peptidasic action:

•precursors of aromatic composts (leucine, ornitine, iso-leucine,valine, methionine)

•oxidizing compost (they contribu te directly to the flavour

•Stimulation of the growth of the leaven and of other bacteria (alanine, valine, serine)

Important metabolic actions

Aromatising

• stimulation of the production of isohalcools by the leaven

• reaction of Maillard and Strecker

Proteolytic

ROLE OF MICRO-ORGANISMS

Production of esopolisaccharids• glucans and/or dextrans

14

LEAVEN* BACTERIA

Saccharomyces

Debariomyces

Hansemula

Pichia

Torulaspora

Cryptococcus

Rhodotorula

Candida

Issatchenkia

Candida

Lactobacillus

Pediococcus

Leuconostoc

Weissella

S. cerevisiae

S. exiguus

L. sanfranciscensis, L. pontis, L. panis, L. plantarum, L. brevis, L. reuteri,

ACID DOUGH MICRO-FLORA

* ACID RESISTANT

15

THE MAKING OF

LEAVEN…

16

1st COOLING

2nd COOLING

3rd COOLING

*region in Northern Italy LEAVEN

LEAVEN CYCLE – WATER COOLING METHODO (Piedmont* school)

IT IS CALLED“ WATER COOLING” BECAUSE THE ACID DOUGH IS KEPT IN WATER, WITH NO NEED TO WRAP THE STARTER OR “MOTHER” IN A CLOTH AND TIE IT WITH A STRING

Dough temperature 22-25°C

MOTHERt 0’

MOTHERAfter 3 hours

18 hours at 4°C

3 h at 30°C – The volume doubles

3 h at 30°C – The volume doubles

3 h at 30°C – The volume doubles

Ratio 1st cooling./flour 1:1 + 0,5 H2O a 30°C

Ratio 2nd cooling./flour 1:1 + 0,5 H2O at 15°C

Flour 1 Water 0,35 at 30°C 1

17

LET’S MAKE THE LEAVEN

JUST AFTER THE COOLING (by immersion)

THREE HOURS AFTER THE COOLING

18

THE STARTER OR “MOTHER” OF LEAVEN (“TIED MOTHER” METHOD)

For the “night rest” the dough can be tied with a string (greater anaerobiosis)

or

kept in a bowl, in different conditions for the growth of lactobacylli.

19

THE STARTER OR “MOTHER”

TIED “MOTHER”

UNWRAPPED “MOTHER”

LEAVEN ADVANTAGES AND DISADVANTAGES

ADVANTAGES

•Softer and more elastic

•Keeps soft for longer

•Better crust

•Can be kept for a long time because it inhibits moulds.

DISADVANTAGES

•Long process

•Difficult to stabilyze

•Risk of contamination

•High M.O. costs

21

DIFFERENT METHODS

THESE ARE NOT THE ONLY LEAVEN-MAKING METHODS. THERE ARE MANY MORE: THE ONLY LIMIT IS OUR IMAGINATION.

GOOD RESULTS ARE OBTAINED WITH KNOWLEDGE AND SKILLS, BUT ABOVE ALL DISCIPLINE AND PERSEVERANCE.