Recreational projects

Historically called the nectar of the gods, mead is an alcoholic drink that used honey as the primary fermentable sugar. This mead used 1.6 kg of honey in a final volume of 4.5 L. Flavourings such as fruit or spices can be added, and 5 g of a mono cultured wine yeast strain (Lalvin 71B in this instance) is then added to begin fermentation. A hydrometer is used to measure alcohol production, relying on the different specific gravity between sugar and ethanol. Alternatively, the alcohol content can be calculated from the available sugars and the alcohol tolerance of the yeast. Though wild yeasts can be used for this process, they are by nature much less consistent with unknown flavour profiles or alcohol tolerances. 

A Korean national dish, kim chi is fermented napa cabbage. Traditionally seasoned with gochujang and gochugaru (Korean fermented chilli paste and chili powder). Wild lactic acid bacteria that live on the surface of the cabbage are selected for by the generation of a salty environment which the comparatively halo-tolerant Lactobacilli can survive. This is achieved by weighing the ingredients and the addition of 2% (w/v) salt to the final weight. The salt draws water from the cabbage, creating a brine that . Fermentation occurs at room temperature for 4-7 days before transfer to the fridge to slow the process down. Though under proper condition the kim chi will not really go bad, the longer it ferments the more sour and soft the cabbage will become. Therefore, the duration of the fermentation is simply a matter of taste.  

A fantastic addition to any sandwich. Most pickles bought in shops are vinegar pickled. Lacto-fermentaion provides a unique flavour and acidity that can't be found otherwise. Safe and effective fermentation is nurtured, as with kim chi, through the establishment of a salty environment that favours halophilic lactic acid bacteria. Unlike Kim chi though, in this instance this is achieved by submerging the pickles in a 3% (w/v) salt solution. Fermentation can occur at room temperature for a week before the process is slowed by refrigeration. Like the kim chi, the longer the fermentation the more sour and soft the pickles become. 

Curing meat can also be performed with the assistance of bacteria. As duck breast is small and safe to eat cured it makes a good candidate for home attempts. Two essential considerations for this are a high salinity and a low moisture. This is achieved by packing the breast in salt for several days which draws out excess moisture and allows the salt to penetrate the meat. Excess salt is then removed and the breast is then wrapped and allowed to dry further and age in a cool environment. Beneficial bacteria then grow, curing the meat and producing a flavour similar to parma ham. As the salinity in this process is comparatively much higher than for kim chi. The growth of cultures is much slower, and curing can take weeks to months of proper aging. 

The SCOBY is the starter culture used to leaven the bread in the production of sourdough. A SCOBY is easily grown at home by mixing an even ratio of flour and water and leaving it at room temperature. Wild yeasts and bacteria present in the flour then begin to grow. Every day half of the substrate is removed and replaced with fresh medium. This is actually similar to how a chemostat operates! After a week, the SCOBY should be bubbling and active enough to begin the process of bread making. As long as you feed the culture daily it can persist almost indefinitely. For longer storage, the culture can also be refrigerated or frozen. 

Though not strictly a biological process, chutneys nonetheless use biological principles for food preservation and enhancement. The combination of vinegar and sugar make an acidic and hydro gyroscopic environment that is inimicable to microbial life. Vinegar can be easily made yourself through the addition of unpasteurised vinegar to any alcoholic drink. The acetic acid bacteria then convert the ethanol to acetic acid in what is called a secondary or double fermentation. Though vinegar is cheap and widely available, this is a great way to make dressings with specific flavours, or to use up homemade alcohols that didn't turn out super palatable.