What kind of acid helps in converting milk into curd

Key concepts Chemistry Food Science Proteins Enzymes Introduction Have you ever poured yourself a cup of milk and instead of a smooth liquid, all you get is clumps? This is usually a sign that the milk has gone bad. And if it smells sour, it probably has. But the physical process of what happened to the milk is called coagulation, which is the mechanism that occurs when proteins in the milk clump. Although you do not necessarily want this in your milk, without coagulation (or curdling) there would be no cheese or yogurt, which is why it is a very important process in the food industry. Wonder how you can make milk curdle—without having it be spoiled? Try this activity to find out! Background Humans have turned milk into a multipurpose liquid. By itself, milk is a nutrient-rich beverage. But when you start treating milk in various processes, all kinds of other products can be created such as butter, yogurt, buttermilk and cheese. Milk mostly consists of fat, protein, lactose (a kind of sugar) and water. The milk fat is suspended in the water as fine droplets, which makes it an emulsion. Milk also contains a lot of proteins that, in this case, are mostly whey and casein. Because casein is poorly soluble in water, its proteins build spherical structures called micelles that allow them to stay in suspension as if they were soluble. With both fat and proteins in suspension, the milk is a white liquid as we know it. The micelle structures, however, can easily be disrupted or cha...

The correct option is D Lactobacillus Milk is converted into curd or yogurt by the process of fermentation. Milk is converted into curd by the help of bacteria called Lactobacillus. These bacteria convert lactose present in the milk into lactic acid. The lactic acid coagulates the milk protein casein and results in the formation of curd.

Acidifying milk — essentially lowering its pH — causes the milk proteins, like casein, to unwind and unfold in a process known as protein denaturing. The unfolded proteins are then free to interact with each other and clump together in a way they could not do when they were properly folded. The milk takes on a curdled appearance from the lumps of proteins that are binding one another. Another way of introducing an acid is through lactose-digesting bacterial cultures, which transform the lactose sugar found in milk into lactic acid, thereby lowering the pH of the milk. These bacterial cultures are used in the preparation of yogurt, certain cheeses, sour cream, and many “cultured” dairy products. Introducing rennet is another way of curdling milk, and requires adding much less acid than if you were to use vinegar, for example. Rennet is actually a complex of enzymes, originally extracted from the stomach of calves, one of which specifically cleaves (cuts) the casein protein found in milk: chymosin. Rennet is often used in the cheese-making process to make batches of cheese with less acid, leading to the growth of more flavor-producing bacteria in the cheese, which have a big impact on taste (as well as texture). Using rennet in the cheese-making process yields cheese curds that are stronger and more rubbery.

Lactobacillus convert milk into curd by the action of lipase and beta-lactamase. Lactobacillus lipase hydrolyzes lactose into lactic acid and beta-lactamase hydrolyzes beta-lactams into antibiotics. Is Curd An Example Of Gel Curd is a type of cheese that is made from milk that has been cultured with bacteria. The curd is then cut into small pieces and put into a saucepan with milk and butter. The mixture is then heated until the butter melts and the milk coats the curd. The curd is then stored in a covered container or jar and used when needed. How Long Should I Ferment Yogurt For Fermenting yogurt takes time and patience. Fermentation occurs when milk is broken down into lactic acid and lactose. Lactic acid is a sour-tasting compound and is created when yogurt is fermented. The longer you wait, the higher the level of lactic acid will be. The more time you give, the less sour-tasting yogurt will be. The recommended time to ferment yogurt is four to eight days. Is Lactobacillus A Curd Lactobacillus is a beneficial bacteria that is typically found in yogurt, sour cream, and other dairy products. It is known to help with digestion and to increase the rates of milk production. Lactobacillus can also help to prevent certain diseases, including lactose intolerance and lactose-induced diarrhea. What Is Precipitation In Milk Precipitation in milk is what happens when water droplets fall from the sky and collect on the surface of milkfat or milk. This liquid contact between rain a...

Hint: Curd is sour in nature. It contains lactic acid which is acidic in nature. So, the pH will change on the side of acids. The milk has a pH of 6. On converting milk to curd, the pH decreases. Complete step by step answer: First let us see what is pH and what is the range. The pH can be defined as the negative logarithm of $$ ion concentration. The pH scale is from 7 to 14. The point on the pH scale 7 is the neutral point. The pH below 7 comes in acidic range and the pH above 7 is alkaline range. The milk has a pH of 6 which means it is slightly acidic in nature. When the milk changes into curd, there are several physical to chemical changes which take place. We all know milk is liquid while the curd is a bit solid. Further, curd is sour while milk is not. Sourness is a property associated with acids. During inoculation of curd in milk, we put Streptococcus lactis and Lactobacillus bacteria in milk. These bacteria multiply and release some organic acids which lower the pH as milk changes into curd. So, the pH decreases when the milk changes into curd. The curd has a pH in range of 4.5 to 4.8. The increase in acidity or we can say the decrease in pH value lead to tangling in milk proteins changing them into solid masses. Note: The NaOH can be used to neutralize lactic acid to delay curdling. Milk contains the protein lactose. The curd formation is an indication that the lactobacilli present are converting lactose into lactic acid.

The principal constituents of milk are water, fat, proteins, lactose (milk sugar) and minerals (salts). Milk also contains trace amounts of other substances such as pigments, enzymes, vitamins, phospholipids (substances with fatlike properties), and gases. The residue left when water and gases are removed is called the dry matter (DM) or total solids content of the milk. Milk is a very complex product. In order to describe the various constituents of milk and how they are affected by the various stages of treatment in the dairy, it is necessary to resort to chemical terminology. This chapter on the chemistry of milk therefore begins with a brief review of some basic chemical concepts. Chemical symbols of some common elements in organic matter: C Carbon Cl Chlorine H Hydrogen I Iodine K Potassium N Nitrogen Na Sodium O Oxygen P Phosphorus S Sulphur Basic chemical concepts Atoms The atom is the smallest building block of all matter in nature and cannot be divided chemically. A substance in which all the atoms are of the same kind is called an element. More than 100 elements are known today. Examples are oxygen, carbon, copper, hydrogen and iron. However, most naturally-occurring substances are composed of several different elements. Air, for example, is a mixture of oxygen, nitrogen, carbon dioxide and rare gases, while water is a chemical compound of the elements hydrogen and oxygen. The nucleus of the atom consists of protons and neutrons, Figure 2.1. The protons carry a p...

Table of Contents • • • • • • • How do we convert milk into curd and what type of change is it? Conversion of milk to curd is a physical change is due to chemical activity. The conversion process is a fermentation process. In this process, the lactic acid bacteria produce Adenosine triphosphate (ATP) from lactose present in milk. Which converts milk into curd in stomach? Lactobacillus Solution: Lactobacillus converts milk to curd by producing lactic acid and reducing the pH of the milk. These bacteria convert the lactose into lactic acid, which imparts the sour taste to curd. How is curd formed 8? The milk will be transformed into curd. This happens due to a bacterium present in the curd called Lactobacillus that converts the lactose sugar present in the milk to lactic acid that in turn provides a suitable acidic environment to coagulate the casein present in the milk, forming curd. Which vitamin is added during curdling of milk? Vitamin E. Hint: When milk is converted into the curd the nutrition value of the curd gets increased as compared to that of milk. Does milk turn into curd in stomach? Chymosin, known also as rennin, is a proteolytic enzyme related to pepsin that synthesized by chief cells in the stomach of some animals. Its role in digestion is to curdle or coagulate milk in the stomach, a process of considerable importance in the very young animal. Which milk is good for curd? Milk converts to curd due to the production of lactic acid. This process of conversion ...

Hint: The most widely used type of fermented milk is yoghurt. A thermophilic fermentation ($45^\circ \ C$) involves yoghurt formation. Lactic acid bacterial cultures, viz. For acid and flavour development, Streptococcus thermophilus and Lactobacillus bulgaricus are used. Complete answer: - Milk is converted by the fermentation process into curd or yoghurt. - Milk consists of so- called casein globular proteins. Because of the chemical reaction between the lactic acid bacteria and casein, the curd forms. - The bacteria use enzymes to extract energy ( ATP) from lactose during fermentation. Lactic acid is the byproduct of ATP production. - Lactic acid acts upon and denatures the globular proteins found in the milk. - The tertiary and quaternary structures of proteins are damaged by this denaturation and globular proteins are converted into fibrous proteins, thereby giving the milk a thick texture due to protein coagulation. Additional information: - The processing of buttermilk includes Lactobacillus spp and Lactococcus lactis mesophilic fermentation. - L. lactis subsp diacetylactis is responsible for the development of diacetyl, a compound that imparts buttery taste to the substance. - A variety of cheeses are commercially available and the formation of all of them involves lactic acid fermentation of milk. - Milk is subjected to fermentation by using Lactococcus lactis or Lactococcus cremoris. The milk proteins on coagulation form curd. - Enzymes like rennin can also be use...