Brewing:
From the workshop:
I always thought that to brew a good cup of coffee, the most important and essential factor is the type of coffee bean only. Through the workshop, I have learned that there are many paraments that can affect a good cup of coffee. They are type of coffee bean, coffee bean grind size, brew ratio, brew time, brew temperature, pressure, water hardness and many more. For example, grind size, the finer the coffee grind, the more the surface area of contact, the more concentrated the coffee. Moreover, the higher the pressure and temperature used, the higher the coffee concertation.
Moreover, from the workshop, I also have learned about the different type of coffee drink. For example, the differences between a latte, cappuccino and flat white. The difference is the amount of foam present. Another example would be the difference between long black and americano. They are basically the same as it contains both espresso and water, just that their preparation process is slightly different, which result in lesser “cameral taste”.
From the readings and video:
Whenever you ask your friend or family member, the reason why they drink coffee in the morning, the most common reason they will give will be that they need a caffeine boost. I always assume that it is a placebo effect to keep people awake and never actually google the science behind it. From videos provided from this chapter, I finally understand how caffeine can keep a person awake. Caffeine has a very similar chemical structure as adenosine. Adenosine is a chemical that each individual human being produces, and it will act as an inhibitory toward the central nervous system (CNS). Adenosine will bind with unique receptors in the brain and causing brain activity to slow down and causing us to become sleepy and lethargic. As the day carry on, more adenosine produces and build up causing us to become more and more tired. Since caffeine has a very similar structure as adenosine, they will be able to bind with unique receptors that are very specific towards adenosine. As a result, caffeine will act as a ‘hindrance’ and block adenosine to attach to the unique receptors causing us to be less sleepy and more awake. Also, when caffeine is bound to the adenosine receptors, it results in the release of more hormones and increases the activity of dopamine, which produce more adrenaline and cause the heart to beat fast and us to feel more happy and “high’’. Apart from the effect of caffeine in the brain, when it enters the liver, it will break down into 3 similar yet different type of molecule. They are structural isomers, but the atoms are connected differently in 3D. The 3 molecules are paraxanthine, theobromine and theophylline, and they will react differently with the human body. Paraxanthine has an ‘awakening effect’ as more epinephrine will be released in the blood. Theobromine will increase the amount of oxygen flow to the brain and Theophylline will cause the heart to beat faster and cause it to contract.
Beyond learning the science behind caffeine, I also learn the process of decaffeination. According to the reading, there are 3 commercial process of decaffeination. The first process involves steaming unroasted bean and using an organic solvent like dichloromethane to extract the caffeine out and the process is called ‘direct decaffeination’. The next process involves soaking coffee beans in hot water for hours and using an organic solvent like the first process to decaffeinate it, and it is known as ‘indirect decaffeination’. The 3rd process involves the use of high pressure and low-temperature carbon dioxide to extract out caffeine. Decaffeination does not completely remove all caffeine in the coffee bean, it will still contain 1.5% to 7.5% of the caffeine in it.
Fermentation:
This week from the workshop I have learned about the fermentation of food, in particular, the fermentation of kombucha tea. Fermentation is a metabolic process whereby carbohydrates and other related compounds are being broken down by bacteria, yeasts or other microorganisms to produce products like organic acid, alcohol and carbon dioxide. Before the start of the fermentation process, the identification of fermented food product substrate and microbe is required.
For example,
| Product | Substrate | Microbe |
| Beer | Barely | Yeast
(Saccharomyces cerevisiae) |
| Yoghurt | Milk | Bacteria
(Streptococcus thermophilus and Lactobacillus bulgaricus) |
| Kombucha | Tea | Yeast and Bacteria
(Lactic acid, acetic acid bacteria and Saccharomyces) |
When yeast is used during the fermentation process, it will produce alcoholic products.
Glucose –>ethanol + carbon dioxide
When bacteria are used during the fermentation process, it will produce mainly acidic products like acetic acid, succinic acid and other products like alcohol, carbon dioxide.
Fermentation can be done in three different conditions, in aerobic (with the presence of oxygen) or anaerobic (without the presence of oxygen) or a mixture of both. For kombucha is a two-stage process, where it is first ferment at aerobic condition then anaerobic. The other factors that affect the fermentation process is the acidity, water activity, nutrient content, temperature, humidity and many more.
For example: Temperature
If the temperature is too high, the micro-organism will die and denature, and the fermentation process will not happen. If the temperature is too low, the micro-organism activity will be slow and sluggish, and fermentation will take longer than expected and contamination might occur. Henceforth, it is important to determine the correct temperature for fermentation so that fermentation can occur smoothly. For kombucha, the optimal temperature for fermentation will be around room temperature (25oc).
To ferment kombucha, we will need tea (1%), sugar (7%) and starter culture (10%) and water. Next as mention previously, we will leave it to ferment at room temperature and in aerobic condition first for 5- 7 days. After 5-7 days, a layer of cellulose pellicle (jelly-like substance) will form, this how we know that the fermentation process is successful. Also, the colour of the mixture will turn darker. If fury substance appears at the top of the mixture, this means that mould has formed. After the first stage fermentation, it is being bottled into an air-sealed bottle where the 2nd stage of anaerobic fermentation will happen. This is to build up the carbonation inside the kombucha.
All in all, from this workshop, I understand how the fermentation process work and how there are many factors that can affect a fermentation process.
Figure 1.0: Kombucha After 1st Stage of Fermentation
(Credit: From Fermentation Workshop Slides)
Figure 1.1: Kombucha After 2nd Stage of Fermentation
(Formation of Carbonation)