CHAPTER 1

INTRODUCTION

The yeast have a lot of economic value to the mankind. They have certain beneficial

as well as harmful activities. Those microorganisms can make leavening of bread

dough and fermentation of the alcoholic beverages, like beer, wine and sake ( Abu

Bakar, H.J.H. 1986). Yeasts is also known as unicellular fungi that can reproduce

primarily by budding and fission, the yeasts do not form their sexual states (spores )

in or on a fruiting body(Walker 2009). S.cerevisiae ( bakers yeast ) is the most

commercially exploited yeast species and it is belong to the fungal kingdom which is

subdivision Ascomycotina. The bakers yeast or brewers yeast species that is

known as saccharomyces cerevisia is being used widely for the food fermentation

industries and also being exploited in the modern biotechnology ( in the production

of recombinant proteins ) and it is also being used as the model eukaryotic cell in the

fundamental biological research (Walker 2009).

According to (Walker,2009) there are about 1000 yeasts have been described,

but the species are being characterized on a regular basis and there is considered

untapped yeasts biodiversity on Earth, for example in 1996, it was estimated that

only 0.065% of yeast genera ( total 62000) and 0.22 % of yeast species ( total

669000) that been isolated. Yeast culture play a major role for the repositories for

invaluable yeasts strains ( germplasm ) but also play an important role for the

biotechnology exploitation.(Barriga 2011).

Yeasts are very useful for the involving in the fermentation processes. Some

yeast are able to convert glucose to ethanol and other volatile compounds and make

them as a vital organism in alcoholic fermentation. The higher alcohol, esters and

other compounds contribute to the aroma of the tapai ( fermented rice product ) and

the present of the sugar and acids also contribute to the flavour of the particular food

( Abu Bakar, H.J.H. 1986). The ragi tapai is consisting of microorganisms such as

bacteria, moulds and yeasts, ragi will form the enzymatic breakdown of the starch

substrate ( rice or cassava ) in the fermentation of tapai (Abu Bakar, H.J.H. 1986).

One of the organisms that related with the tapai fermentation is the yeast that is

known as saccharomycopsis fibuligera. This yeast is isolated from ragi and its

product, tapai ( Adang 1991 ).

Yeast is a single-cell micro-organism. Water helps yeast to convert sugar

into carbon dioxide and alcohol in anaerobic process and form water and carbon

dioxide when oxygen is present. When dry, yeast becomes inactive and they wake

up when water and food such as sugar and minerals are present at certain suitable

temperatures. Fermentation includes many enzymes which are large protein

molecules for catalysing specific reactions. If there is no water that available, no

reaction will take place.

Research objectives

1) To determine the value of moisture, ash, volatile matter and fixed carbon in

bakers yeast and ragi by using proximate analysis method.

Research objectives

It is important to know the moisture, ash, volatile matter and fixed carbon in

the bakers yeast and ragi for tapai (fermented alcoholic beverage) because it will

affect the quality of the bread and beverage. For example, if there are no moisture at

all in bakers yeast and ragi the ability of the yeast to grow will be decrease, but if

there are too much moisture the shelf life of the yeast and ragi will be short. It also

same goes to ash content in the bakers yeast and ragi. High ash content can indicate

potential for problems with handling and disposing of large amount of ash residues

produced. Volatile matter and fived carbon values that contain in the bakers yeast

and ragi is also important in order to make a good quality bakers yeast and ragi.

Scope of research

In this research, the moisture, ash, volatile matter and fixed carbon values that

contain in the bakers yeast and ragi is analysed by using the proximate analysis

method that as defined in ASTM D121. The bakers yeast that is being used in this

experiment is from local bakers yeast that is manufactured in Lebuh India Kuching,

Sarawak and called as ragi kering ( dry yeast ) and the ragi for tapai is also from

local ragi that is manufactured in Jln Meranek, Kuching Sarawak.

For determining of the moisture content in both of the yeast, the conventional

ovens or microwaves ovens is used in this experiment. The moisture is vaporize

during heating at certain temperature. The values of the moisture can be expressed in

term of percentage, by weight, of the sample used in the test. The temperature that is

used to determine the moisture content in this analysis is about 110 C.

Ash is the residue remaining after the combustion of sample under some

conditions. The sample is inserted in cold furnace and the temperature is raised at

such rates until reaches 550 C for an hour.

For volatile matter determination, the sample is inserted inside the furnace

chamber with temperature that must be maintained at 950 C for exactly 7 minutes.

The mass loss that is recorded in this method is includes the residual moisture and

the water of hydration of mineral matter.

The value of fixed carbon can be obtain by subtracting the sum of the

percentages of moisture, ash, and volatile matter from 100. This value is can be

considered as the amount of carbon residue that remains after the volatile matter

analysis.

Barriga, E. J. C. (2011). "Yeasts Biodiversity and Its Significance: Case Studies in Natural and

Human-Related Environments, Ex Situ Preservation, Applications and Challenges."

CHANGING DIVERSITY IN CHANGING ENVIRONMENT: 55.

Walker, G. M. (2009). "Defining statement." Yeasts: 14.