AT Starbucks, seven principles of coffee brewing wisdom are strictly observed to provide guests with perfect coffee.

1. To avoid bitter flavour, never boil coffee. The ideal temperature should be controlled at about 90 to 96 degrees C.

2. Never re-heat coffee. We suggest making a proper amount of coffee, assuring the freshest quality. Keep coffee at 86 degree C to get the best flavour.

3. Use fresh and cool water to brew coffee. Water accounts for 98 per cent of every cup of coffee. If the water has strange smell, you should use pure bottled water.

4. Coffee powder can't be used twice, or the coffee will be very bitter.

5. Choose the grind-setting according to the different coffee makers. Too finely ground coffee beans will lead to bitterness, while too large grains will block the filter and hinder the aroma.

6. Every 10 grams (about too spoons) ground beans requires six ounces of water. This percentage is always useful no matter how much coffee you brew.

7. Coffee can only be kept warm on the stove for about 20 minutes. The flavour will change if it stays there longer, while vacuum flasks can help maintain flavour.