Monday, October 28, 2019

Food Fermentation Atau Fermentasi (Penanganan Hasil Perikanan)



What are fermented foods?

Foods or food ingredients that rely on microbial growth as part of their processing or production

 

Food Fermentation

         Metabolic activities occur during fermentation that:

       Extend shelf life by producing acids

       Change flavor and texture by producing certain compounds such as alcohol

       Improve the nutritive value of the product by:

         Microorganisms can synthesize vitamins

         Breakdown indigestible materials to release nutrients, i.e., bound nutrients

 

Fermented Foods

         Foods fermented by yeast

       MaltàBeer

       Fruit (grapes) à Wine

       Rice à Saki

       Bread dough à Bread

         Foods fermented by mold

       Soybeans à Soy sauce

       Cheese à Swiss cheese

         Foods fermented by bacteria

       Cucumbers à Dill pickles

       Cabbage à Sauerkraut

       Cream à Sour cream

       Milk à  Yogurt

 

Food Fermentations – Definitions

         Anaerobic breakdown of an organic substrate by an enzyme system in which the final hydrogen acceptor is an organic compound



         Biological processes that occur in the dark and that do not involve respiratory chains with oxygen or nitrate as electron acceptors

 

Food Fermentations – Biochemistry 

Sugars … Acids … Alcohols, Aldehydes

Proteins … Amino acids … Alcohols, Aldehydes

Lipids … Free fatty acids … Ketones

 

Respiration vs. fermentation

Refer to how cells generate energy from carbohydrates

RESPIRATION:

          Glycolysis + TCA (Kreb’s) Cycle + Electron Transport

          O2 is final electron acceptor

          Glucose is completely oxidized to CO2



“Fermentation” is used broadly – describe where the use of the word comes from.

ATP=main chemical energy in a cell.

 

         Some organisms (facultative anaerobes), including yeast and many bacteria, can survive using either fermentation or respiration.

         For facultative anaerobes,
pyruvate is a fork in the
metabolic road that leads
to two alternative routes.




Respiration vs. fermentation

FERMENTATION:

          An organic compound is the final electron acceptor

          Glucose is converted to one or more 1-3 carbon compounds



In this class, we will deal mostly with m/o that are generating energy by fermentation.

Why would a cell ferment vs. respire (since less energy is produced)?  Can’t respire, can, but no oxygen present.

Produces less energy than respiration, but no oxygen required.

From food standpoint, byproducts are important.

 

         During lactic acid fermentation, pyruvate is reduced directly by NADH to form lactate (ionized form of lactic acid).

       Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt.



         In alcohol fermentation, pyruvate is converted to ethanol in two steps.

       First, pyruvate is converted to a two-carbon compound, acetaldehyde by the removal of CO2.

       Second, acetaldehyde is reduced by NADH to ethanol.

       Alcohol fermentation
by yeast is used in
brewing and
winemaking.



 

         Carbohydrates, fats, and proteins can all be catabolized through the same pathways.



Respiration vs. fermentation

Some cells can respire and ferment sugars for energy.  The cell will do one or the other depending on the conditions. 

Example:  Saccharomyces cerevisiae (baker’s, ale and wine yeast).

Some cells can only respire or only ferment sugars for energy.

Example: Lactic acid bacteria produce energy by fermentation.

In this class, we will deal mostly with m/o that are generating energy by fermentation.

Why would a cell ferment vs. respire (since less energy is produced)?  Can’t respire, can, but no oxygen present.

Produces less energy than respiration, but no oxygen required.

From food standpoint, byproducts are important.

 


Typical fermentation process

         substrate disappears as cell mass increases

         sugar, then other small molecules, then polymers used

         primary metabolic products (acids) accumulate during growth

         pH drops if acids produced

         growth and product formation stop as substrate is depleted

         microbial succession depends on substrate and acid levels

 

Food Fermentations

In food fermentations, we exploit microorganisms’ metabolism for food production and preservation.

Where do the microorganisms come from to initiate the food fermentation?

Two ways to initiate a food fermentation….

...traditional & controlled fermentations

Fermentative energy pathways that we are expoiting

 

Controlled vs. Natural Fermentation

         Natural fermentation

       Create conditions to inhibit undesirable fermentation yet allow desirable fermentation

       Examples:

         Vegetable fermentations

       Vegetables + salt

 

Controlled vs. Natural Fermentation

         Controlled fermentation

       Deliberately add microorganisms to ensure desired fermentation

         Example: fermented dairy products

       Lactose … Lactic acid

       Starter culture

»       Lactics or Lactic starter or Lactic acid bacteria (LAB)

 

Traditional Fermentation



Disadvantage:  Process and product are unpredictable depending on source of raw material, season, cleanliness of facility, etc. 

Advantage:  Some flavors unique to a region or product may only be attained this way.

Relies on m/o naturally found in the raw material.

Have been going on for thousands of years.  Long before we knew what bacteria and fungi are.

Conditions adjusted so that desirable microorganisms grow.

 

Controlled Fermentation



Advantage: – uniformity, efficient, more control of process and product

 

Disadvantage: Isolating the right strain(s) to inoculate is not always easy.  Complexity of flavors may decrease.

Large numbers of desirable m/o’s are added to the raw material.

This is a starter culture. 

It helps if raw material is sterile or has reduced natural microflora, so that the added m/o’s dominate quickly.

Conditions adjusted so that desirable (starter culture) m/o’s grow.

 

Controlled Fermentations: Starter cultures

Two main starter culture types are used to inoculate the raw material:

1.   Pure microbial cultures prepared specifically for a particular food fermentation.  (More details on these later.)

2.   “Backslop” method = Using some of the product from a previous successful fermentation to inoculate the next batch of raw material.

 

Controlled Fermentation: pure cultures



Provides most control

First used in the 1890s.

 

Controlled Fermentation: “backslop” method



Can pass on undesirable organisms too.

Balance of live organisms may change in final product.

Can pass on undesirable organisms too.

Balance of live organisms may change in final product.

Used in the old days.  Not common now on an industrial scale because of the risk of contamination.

 

Summary

         Why we ferment foods

         Microbial energy metabolism:       respiration vs. fermentation

         Traditional fermentations – indigenous microflora

         Controlled fermentations – starter culture added

 

Food products

from milk:

cheese, yogurt, sour cream, buttermilk

lactic acid bacteria (lactobacilli, streptococci)

meats:

fermented sausages, hams, fish (Asia)

lactic acid bacteria (lactobacilli, pediococci), molds

 

beverages:

         beer  (yeasts make ethanol)

         wines (ethanol fermentation from grapes, other fruits)

         vinegar (ethanol oxidized to acetic acid)

         breads:

         sourdough (yeast + lactobacilli)

         crackers, raised breads (yeasts)

 

single cell protein:

how cheaply and efficiently can cells be grown?

waste materials as substrate (bacteria, yeast, molds)

sunlight and CO2 (algae)

uses in animal feeds (frequently) or human foods

prefer protein to whole cells

high nucleic acids --> kidney stones,

 

Organic acids

         Primary Metabolites

         Organic acids are. (primary products of metabolism).

          During the log phase of growth the products produced are essential to the growth of the cells.

         Secondary metabolites:

(Secondary products of metabolism)

         During the stationary phase some microbial cultures

synthesize compounds which are not produced during

the trophophase* and do not appear to have any

obvious function in cell metabolism.(idiophase*)

 

Publisher

Gery Purnomo Aji Sutrisno

FPIK Universitas Brawijaya Angakatan 2015

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