What is the difference between oxidation and fermentation

Thus, the conservation of polyphenols in the tea will not harm the quality of the tea. In the production of tea, the enzyme known as polyphenol oxidase is of great importance. When the metabolites known as catechins in tea come in contact with oxygen, the oxidase starts to act, producing polyphenols of higher molecular weight.

These polyphenols are thus capable of adding aroma and colour to the black tea. However, in tea production, oxidation takes place under controlled conditions, which differentiate between different tea varieties. Fermentation is the process that takes place under anaerobic conditions.

Therefore, it occurs in the absence of molecular oxygen. Many microbes, plants and human muscle cells are capable of undergoing fermentation. During fermentation, conversion of sugar molecules to alcohols and acids takes place. The chemical reaction has great usage in the industrial production of dairy products, bakery products and alcoholic beverages. In the natural context, there are two main types of fermentation, both of which require the involvement of enzymes. These two processes are lactic acid fermentation and ethanol fermentation.

In lactic acid fermentation, conversion of the pyruvate sugar moiety into lactic acid takes place under the influence of lactic acid dehydrogenase. Lactic acid fermentation primarily occurs in bacteria and in human muscles.

Oxidation is a bio-chemical, enzymatic activity. In oxidation the host material absorbs oxygen and as a result, transforms. Please see the following points for a better understanding of oxidation. Let us cut an apple or banana and leave the cut side open to the air. The cells exposed to air shall absorb oxygen and soften up. The cut fruit then turn brown. This is a very simple form of spontaneous negative oxidation.

If we dry up the apple slices in a controlled manner, say in a dryer, then we can term this as a controlled negative oxidation. In fact, spontaneous oxidation process starts as soon as we pluck the tea leaves. It continues throughout the withering phase of white, oolong, and black teas. Manufacturers dry or pan fry the white or green teas sooner than later. Thus, the the tea maker preempts any possibility of further oxidation.

They apply heat to stop the activities of the enzymes which is called de-enzyming. Thus the polyphenols do not change or alter in green or white tea and hence the leaves retain their green color. On the other hand, controlled oxidation is one of the most important steps of oolong and black tea manufacturing process. To produce black tea, withered leaves are subjected to crushing, tearing, cutting CTC or rolling operations to achieve faster oxidation.

This process damages the cell walls of the leaves extensively. As the oxidation process is started officially, oxygen comes in contact with the exposed bruises in the leaves and the leaves starts to turn brown.

With the CTC or rolling operations damaging the cell walls of the tea leaves, the mixing of the polyphenols and polyphenol oxidases also intensifies. This in turn accelerates the pace of oxidation. Now you can see, this process does not meet any preconditions of fermentation. So, you guessed it right, this is nothing but oxidation, which requires abundant moist and oxygen-rich air.

Now we learn that, whatever process the maker uses in producing black tea is oxidation only, and has nothing to do with fermentation! When the catechins come in close contact with the respective enzymes in presence of oxygen, they produce polyphenols of higher molecular weight. However we can make it possible if we keep the temperature and humidity at an optimum level. As the polyphenols come in contact with oxygen, the unique flavor and color components along with other distinctive characteristics start to manifest.

This is exactly what we look for in a cup of black tea. So what is the difference between oxidation and fermentation? If I leave my metal bike outside in the rain, it will rust. That's oxidation. If I coat my bike with sugar and let some wild bacteria start to grow…then I have a bad example. Back to drinks. Fermentation involves bacteria or yeast that eat sugars to produce carbon dioxide, and in the case of yeast--alcohol.

Air can't diffuse through the oil to the medium How would you determine that a bacteria can oxidize and ferment? If the bacteria turn the O-F tube yellow in aerobic and anaerobic condition How would you know if the bacteria is only oxidize or only ferment?

If the bacteria only turn the O-F tube yellow in either aerobic or anaerobic condition What does it mean when the aerobic and anaerobic O-F tube both turn green? Bacteria can't oxidize or ferment the sugar What does it mean if the top of the O-F test tube turn blue?

Alkaline product from amino acid degradation Which bacteria does O-F test differentiate? Fermentative Enterobacteriaceae from the oxidative Pseudomonas and Bordetella, and the non reactive Alcaligenes and Moraxella What is catabolism?

Bacteria that can degrade amino acid turn the O-F tube basis and blue.