Beer phenols are chemical compounds, similar in structure to alcohols, that are generated by yeast during fermentation. In certain styles of beer, such as Bavarian hefeweizens and wit beers, phenol flavors such as bubblegum, banana and clove are considered desirable; but in other styles they are considered to be an off flavor or flaw. Causes of unwanted phenols include wild yeast or bacteria, chlorine, and excess sanitizer.
Cloying is a term used to describe a beer that is too sweet or too malty. This typically occurs when there were not enough hops to properly balance out the sweetness, if the mash temp was set too high and created too many unfermentable sugars, or if the yeast was not able to carry out a proper fermentation and too much sugar was left behind in the finished beer.
Autolysis is the destruction of a cell by the actions of its own enzymes. In brewing, autolysis typically occurs when yeast cells either decay over time or destroy each other. When the outer wall of the yeast cell is degraded and can no longer contain itself, it releases off flavors and odors into the beer. These odors are typically described as rubbery in aroma.
Autolysis is most common in aged beers, but can also occur in a fresh beer due to a variety of factors including unhealthy\aged yeast, stress caused by too rapid of a fermentation, excessive temperature changes and high alcohol levels. One of the best ways to reduce the impact of autolysis is to conduct a secondary fermentation as a means of removing the beer from the yeast cake. Other ways of reducing the impact of autolysis is proper aeration of the wort prior to fermentation, avoiding oxidization, keeping a consistent and appropriate fermentation temperature, and properly regulating the temperature of your finished beer.
An ale is a beer that has been fermented using a top fermenting yeast. Ale yeasts are typically more resilient to warmer temperatures then their lager counterparts and are usually fermented at a temperature range of 65-75 F. Since the yeast is more active at higher temperatures, an ale ferments much quicker then a lager.
Examples of ales include golden ales, pale ales, India pale ale, old ale, Belgian ale and barley wines.
Something to keep in mind when fermenting an ale is that ale yeast can ferment beer above a temperature of 75 F, but when doing so it will oftentimes create undesirable esters and off flavors. Also, liquid ale yeast is vulnerable to high temperature, and it should be refrigerated to maintain its viability in transit and in storage. Due to the delicate nature of liquid yeast, I always create a yeast starter to verify its viability prior to pitching it in the cooled wort.