Role of LAB — Core Principles
Core Principles
Lactic Acid Bacteria (LAB) are a crucial group of microorganisms, primarily bacteria, known for their ability to convert sugars into lactic acid through a process called lactic acid fermentation. This metabolic activity is fundamental to household food processing, transforming raw ingredients into a variety of fermented products.
In dairy, LAB like Lactobacillus and Streptococcus ferment lactose in milk, producing lactic acid that causes casein proteins to coagulate, forming curd or yogurt. This acidification not only creates the characteristic texture but also acts as a natural preservative by inhibiting the growth of spoilage and pathogenic microbes.
Beyond dairy, LAB are vital for fermenting plant-based foods such as dosa and idli batter, pickles, and sauerkraut, contributing to their unique flavors, extended shelf life, and improved digestibility.
Many LAB are also recognized as probiotics, offering health benefits like enhanced gut health and nutrient absorption. Their role is multifaceted, encompassing preservation, flavor development, and nutritional enrichment, making them indispensable in traditional and modern food systems.
Often confused with
Side-by-side differences the NEET paper likes to test.
| Aspect | Role of LAB | Alcoholic Fermentation (by Yeast) |
|---|---|---|
| Primary Microorganism | Lactic Acid Bacteria (LAB) (e.g., Lactobacillus, Streptococcus) | Yeast (e.g., Saccharomyces cerevisiae) |
| Main End Product(s) | Lactic Acid | Ethanol and Carbon Dioxide ($CO_2$) |
| Oxygen Requirement | Facultative anaerobic or microaerophilic | Facultative anaerobic (prefers aerobic, but can ferment anaerobically) |
| Impact on pH | Significantly lowers pH (acidification) | Slightly lowers pH (due to some acid production), but primarily produces alcohol |
| Common Food Applications | Curd, yogurt, cheese, pickles, sauerkraut, dosa/idli batter | Bread (leavening), beer, wine, other alcoholic beverages |
| Texture Contribution | Coagulation of proteins (e.g., curdling milk) | Gas production for leavening (e.g., spongy bread) |
While both lactic acid fermentation by LAB and alcoholic fermentation by yeast are crucial anaerobic processes in food processing, they differ fundamentally in their primary microbial agents and end products.
LAB primarily produce lactic acid, leading to acidification, preservation, and protein coagulation (as seen in curd). Yeasts, on the other hand, produce ethanol and carbon dioxide, which is vital for leavening (in bread) and alcoholic beverage production.
Understanding these distinctions is key to appreciating the diverse roles of microbes in food.
Why it is tested: For NEET, understanding the distinct biochemical pathways and their specific applications is crucial. Questions often test the ability to differentiate between these processes based on their end products, microbial agents, and the resulting changes in food characteristics. For instance, knowing that LAB cause curdling and yeast causes bread to rise is a common point of inquiry.