If you’ve ever wondered about the name of acid in curd, the answer is straightforward — it’s lactic acid. Its chemical formula is CH₃CH(OH)COOH, and the IUPAC name is 2-Hydroxypropanoic acid. But there’s much more to this molecule than a simple label.
Which Acid Is Present in Curd?
Lactic acid forms when bacteria ferment lactose, the natural sugar in milk. Specifically, Lactobacillus bulgaricus and Streptococcus thermophilus break lactose into glucose and galactose, then convert them into lactic acid. This lowers the pH to roughly 4.0–4.5, causing milk proteins (casein) to coagulate. That’s your curd.
Worth noting: Karl Wilhelm Scheele first isolated lactic acid back in 1780 from sour milk. So this chemistry has been understood for centuries.
Is Curd the Same as Yoghurt?
Not exactly. In India, curd is typically made by adding a spoonful of previous curd to warm milk — a spontaneous fermentation with mixed bacterial cultures. Yoghurt, on the other hand, uses specific controlled starter strains. The acid is the same, but concentration can differ. Yoghurt tends to be slightly more acidic than homemade curd, while buttermilk sits somewhere in between.
Which Acid Is Present in Tomato, Tamarind & Other Foods?
People often confuse these. Tomatoes contain citric and oxalic acid. Tamarind has tartaric acid. Vinegar — acetic acid. Ant stings deliver formic acid. And gastric juice in your stomach? That’s hydrochloric acid, an inorganic one. Lactic acid, citric acid, and tartaric acid are all organic acids.
Is Curd Good or Bad for Acidity?
Surprisingly, curd can actually help with acid reflux. A 2018 study published in Nutrients showed that fermented dairy products improve gut microbiome diversity. The probiotics in curd aid digestion and may reduce symptoms of bloating. People with lactose intolerance often tolerate curd better than milk — bacteria have already broken down much of the lactose during fermenation.
L-Lactic Acid vs D-Lactic Acid
Lactic acid exists as two stereoisomers. Bacterial fermentation in curd mostly produces the L(+) form, which human body metabolizes easily. The D(-) form is less common and harder to process. This distinction matters in food science and is often overlooked.
Beyond Food: Industrial Uses
Lactic acid isn’t just about curd. It’s registered as food additive E270. It’s used in cosmetics as a gentle exfoliant, in biodegradable plastics (PLA), and even in pharmaceutical formulations. The global lactic acid market was valued at over $2.9 billion in 2022 according to Grand View Reserch.
Don’t confuse dietary lactic acid with the lactic acid that builds up in muscles during exercise — same molecule, different context entirely.
FAQ
What if I Eat 500g Curd Daily?
Moderate consumption is generally safe, but 500g daily may cause digestive discomfort in some people. Balance is key.
Which Gas Is Present in Curd?
Carbon dioxide (CO₂) can form during fermentation, though in small amounts compared to yeast-based processes.
Name of Acid in Curd — Class 9 and 10?
For CBSE and competitive exams like NEET or FCI, the answer is always lactic acid with formula CH₃CH(OH)COOH.
Final Thoughts
The acid in curd is lactic acid — a simple organic compound with a surprisingly wide range of applications. From your kitchen to industrial bioplastics, this molecule plays a bigger role than most people realize. Understanding how it forms through bacterial fermentation helps you appreciate what’s really happening every time milk turns into curd.
