Vinegar processing
Vinegar is the result of two stages of fermentation. Yeast converts sugars into ethanol anaerobically in the first stage. In the second step, bacteria from the genera Acetobacter and Gluconobacter oxidize ethanol to acetic acid aerobically. The residual ethanol content in wine vinegar must be less than 0.5% and less than 1% in other vinegar.
Vinegar is an aqueous solution of acetic acid, typically containing 3-5% acetic acid, produced by a double fermentation: simple sugar is converted to ethanol using yeast, and ethanol is then converted to acetic acid by acetic acid bacteria. Common commercial types include white vinegar, apple cider vinegar, balsamic vinegar, wine vinegar, rice vinegar and malt vinegar, each defined by the raw material feeding the first fermentation.
The two fermentation stages govern plant design. In alcohol fermentation, yeast enzymes use the sugar present in fruit to produce alcohol (ethanol) and carbon dioxide gas, following sugar (fructose, glucose) to ethanol + 2CO2. In acetic acid fermentation, the alcohol produced reacts with atmospheric oxygen through the action of acetic acid bacteria to give acetic acid and water, following ethanol to acetic acid + H2O. Because the second stage depends on oxygen contact, aeration and vessel configuration are central process decisions.
A typical production line runs through harvesting, washing and grading, mashing, settling, fermentation and ageing, and bottling. Vinegar produced by the quick process is kept for ageing for about six months.
Post-fermentation handling determines shelf stability and appearance. Before bottling, the vinegar is made sparkling clear through clarification, and it is pasteurized by heating in an open vessel to about 60 degree C, then cooled and bottled. The main spoilage risk is lactic acid producing bacteria, which grow initially and spoil the vinegar. PMG Engineering delivers end-to-end engineering design and construction management projects in the food and beverage industry, covering process engineering, project management, automation, food safety, and mechanical and electrical.