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Institut de Tehnologie du Cambodge Génie Chimique et Alimentaire

Lecturer: Dr. HUL SeinghengGroup 7: PENG Chanthol

PHEAP KanikaPHEAP Theavy PHOEURN VuthamryPOENG Huykheng

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TOPIC:

YEAST PRODUCTION

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INTRODUCTIONYeast

•Unicellular-Fungi•Eukaryotic•Facultative anaerobes•Capable of forming colonies on solid culture media

Classification of Bakery’s yeast•Kingdom: Fungi•Phylum: Ascomycota•Subphylum: Saccharomycotina•Class: Saccharomycetes•Order:Saccharomycetales•Family: Saccharomycetaceae•Genus: Saccharomyces• Species: S. cerevisiae

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INTRODUCTION

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INTRODUCTION

Baker’s yeast is manufactured by six major companies in the United States. Those are Universal Foods (Red Star Yeast), Fleischmanns, Gist-Brocades, Lallemand (American Yeast), Minn- dak, and Columbia.

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PRODUCTION OF BAKER’S YEAST

As a result of grain shortages resulting from World War I a shift was made from the use of grain to the use of beet molasses, supplemented by ammonia and phosphate.

There are two major steps in the development of baker’s yeast technology:• Vienna process • Classical batch method and Zulaut method.

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PRODUCTION OF BAKER’S YEAST

Yeast Strain UsedNowadays, the most common baker’s yeast strain is

Saccharomyces cerevisiae. Yeast strains used for the modern fast-rising dough

have been developed with the following properties:1) Ability to grow rapidly at about T= 20-25oc2) Ability to produce large amount of CO2 , rather

than alcohol3) Good keeping qualities

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PRODUCTION OF BAKER’S YEAST

4) High invertase and other enzyme activity to hydrolyse the higher glucofructans rapidly

5) Ability to grow and synthesize enzyme and coenzymes under the anaerobic conditions of the dough

6) Ability to resist the osmotic effect of salts and sugars in the dough

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PRODUCTION OF BAKER’S YEAST

SubstrateThe substrate usually used for baker’s yeast

production is molasses.When 2 types of molasses are simultaneously

available, they are then mixed in equal amounts so that the nutritional deficiency of one type is made up by the other.

When only 1 type of molasses is available deficiencies are made up by adding appropriate nutrients.

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PRODUCTION OF BAKER’S YEAST

The molasses is: Clarified : to impart undesirable color to the yeastand to reduce foaming.

Sterilized (is achieved by heating at 100oc-110oc for about 1h) after pH adjusted (by adjusting to pH 6-8) to prevent caramelization of the sugar.

P, NH4 , Mg, K, Zn, thiamin are added for maximum productivity to be mixed molasses.

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Fermentor processes

1lb dry wt. of yeast required 4.3lb of molasses, 0.9lb of NH3, 0.3lb of NH4H2PO4 , 1.1lb of (NH4)2 SO4 and 60lb of air.

Steam sterilized fermentor

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PRODUCTION OF BAKER’S YEAST

Harvesting the yeastThe period of fermentation varies from 10 to 20hr.

Process:The fermentation broth is cooledStoring cell in centrifugal separatorIncluding waterCentrifugation until they are lighter in color

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PRODUCTION OF BAKER’S YEAST

Adding before filtration 0.2-0.6% sodium chloride

Passing over a rotary vacuum filter or through a filter press

Excess salt is removed during filtration by spraying water over the filtered yeast

Yeast production

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PRODUCTION OF BAKER’S YEASTPackagingThe yeast is packaged as compressed yeast or

active dry yeast.Compressed yeast: is mixed with fine particles

of ice, starch, vegetable oils which all help to stabilize it.

It is then compressed into blocks of small (1-5 Ib) blocks for household use or large (up to 50 Ib) for factory bakery operations.

Store at – 7 to 0°C and transported in refrigerated vans.

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PRODUCTION OF BAKER’S YEASTActive dry yeast: is more stable in that it can be used

in areas or countries where refrigeration is not available.

Compressed yeast Active dry yeast

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FOOD YEASTSImportant : to provide protein; to impart flavor and

to supply vitamins especially B-vitamins.Food yeasts have several synonyms: dried yeast,

inactive dried yeast, dry yeast, dry inactive yeast, dried torula yeast, Saccaromyces siccum, sulfite yeast, wood sugar yeast, and xylose yeast.

Yeasts used as food yeasts: Saccharomyces cerevisiae, Saccharomyces carlbergiensis, Saccharomyces fragilis* Candida tropicalis

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Ethanol: Substrate for food yeasts production that is used only by:

Saccharomyces fragilis Candida tropicalis**.

Note: * can utilize lactose for fermentation of whey.**

most widely used in food yeast preparation.

*** using in U.S is the preference.

FOOD YEASTS

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FOOD YEASTSSubstrate most commonly used for food yeast production are:

molasses: the fed batch method. sulphite liquor: the continuous

using Candidautilis fermentation. wood hydrolysate and whey. Using saccharomyces lactis, Kluyveromyces***,

Other unconventional sources have been developed such as: hydrocarbons, alcohol and wastes of various types. But only the most commonly substrate will be discussed.

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FEED YEAST

• Feed yeasts is used to produce animal food.•Several thousands tons of yeasts are recovered from breweries around the world annually.•Cells are recovered by centrifugation and spray or drum-dried

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ALCOHOL YEASTS Alcohol yeasts are those to be used in beer

brewing, wineries and distilleries for spirits of industrial alcohol.

The production of alcohol yeasts, the aim is cell production

The yeasts used are specially selected strains of the following:

1. Brewing: Saccaromyces cerevisiae, Saccharomyces uvarum carlbergensis S.uvarum.

2. Wine: Saccharomyces cerevisiae, Sacch.bayanus, Sacch.beticus, Sacch.elipsoides

3. Distillery yeasts: Saccharomyces cerevisiae

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ALCOHOL YEASTS

• The medium used in the multiplication of the yeast is made of materials to be found in the final fermentation.

• Alcohol yeasts are usually recovered and reused for several rounds of fermentation before being discarded.

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YEAST PRODUCTS

Yeasts are used in the various products like:◦ Food◦ pharmaceutical and related industries.

Yeast extracts are used in the preparation of soups, sausages, gravies, to which they impart a meaty flavor.The extracts may be obtained by autolysing the yeast and thereafter spray-drying or drum-drying with or without extracting soluble materials from the autolysate. Yeast extracts are consumed for dietary purposes on pharmaceutical grounds as a source of vitamins, mainly vitamin B12.

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CONCLUSION

The important of yeast in industrial food for human and animal.

How yeast is produced involving substrate, fermentor processes, harvesting and packaging.

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Thank For Your Attentive Listening!

Welcome for questions