Microbes in Household Products Questions in English

(A) $Streptococcus$ $lactis$ is a lactic acid bacterium $(LAB)$.
It converts the lactose sugar present in milk into lactic acid.
This lactic acid causes the coagulation of milk protein,known as casein,which results in the conversion of milk into curd.

(A) The production of $Casein$ is a chemical process involving the precipitation of milk proteins (primarily $Casein$) using acids (like lemon juice or vinegar) or enzymes (like rennet). It does not require the fermentation activity of fungi or microorganisms. In contrast,the production of $Curd$ requires $Lactic$ $Acid$ $Bacteria$ $(LAB)$,$Cheese$ production involves specific microbial cultures (bacteria or fungi),and $Wine$ production requires the fermentation activity of yeast (a fungus).

(A) $Lactobacillus$ bacteria,commonly known as Lactic Acid Bacteria $(LAB)$,grow in milk and convert it into curd.
They produce acids that coagulate and partially digest the milk proteins.
$LAB$ also plays a beneficial role in checking disease-causing microbes in our stomach.
Therefore,$Lactobacillus$ is the correct answer.

(D) Milk is converted into curd primarily by Lactic Acid Bacteria $(LAB)$ such as $Lactobacillus$ species (e.g.,$Lactobacillus$ $acidophilus$ or $Lactobacillus$ $casei$) and $Streptococcus$ $lactis$. These bacteria grow in milk and convert lactose sugar into lactic acid,which coagulates the milk proteins (casein) to form curd. Since none of the options $(A, B, C)$ list these specific bacteria,the correct answer is $D$.

(A) The preparation of Idli involves the fermentation of rice and black gram batter.
This process is primarily carried out by lactic acid bacteria.
$Leuconostoc$ $mesenteroides$ is a well-known bacterium responsible for the fermentation of the batter,which gives Idli its characteristic texture and flavor.
$Clostridium$ species are generally associated with spoilage or anaerobic decomposition and are not used in the preparation of food products like Idli.
Therefore,the correct option is $A$.

(B) The process of bread making involves the use of yeast, specifically $Saccharomyces$ $cerevisiae$, which is commonly known as baker's yeast.
During the fermentation process, yeast breaks down the sugars present in the dough into ethanol and $CO_2$.
The release of $CO_2$ gas creates bubbles within the dough, which causes the bread to rise and become porous and soft.

(A) $S. \text{cerevisiae}$ is commonly known as Baker's yeast, brewer's yeast, or distiller's yeast.
In the process of making bread, an aerobic strain of this fungus is used to facilitate fermentation, which produces carbon dioxide, causing the dough to rise.

(B) The correct answer is $B$. Yeast,green leafy vegetables,milk,yoghurt,pulses,egg white,liver,kidney,and meat are rich sources of riboflavin (Vitamin $B_2$).

(B) In olden days,cheese was prepared by using the enzyme $Rennet$,which is extracted from the lining of the stomach of young calves,sheep,or goats. This enzyme contains $Chymosin$,which helps in the coagulation of milk proteins to form curd,a primary step in cheese production.

(D) The process of curdling milk involves the conversion of lactose sugar into lactic acid by Lactic Acid Bacteria $(LAB)$.
Common examples of $LAB$ include species of $Streptococcus$ and $Lactobacillus$.
$Streptococcus$ $lactis$,$Streptococcus$ $thermophilus$,and $Lactobacillus$ $lactis$ are all known to play a role in the fermentation of milk into curd.
Therefore,all the listed microorganisms contribute to the process of curdling.

(D) Lactic acid bacteria $(LAB)$ are used in the formation of cheese.
These bacteria grow in milk and convert it into curd or cheese by fermenting the lactose sugar present in the milk into lactic acid.
This process leads to the coagulation and digestion of milk proteins,which is essential for cheese production.

(B) The production of leavened bread involves the use of baker's yeast, scientifically known as $Saccharomyces \text{ } cerevisiae$.
During the process, yeast ferments the sugars present in the dough, producing carbon dioxide $(CO_2)$ and ethanol.
The release of $CO_2$ gas causes the dough to rise (leaven), resulting in the soft and porous texture characteristic of bread.

(D) Yoghurt is a form of fermented milk product.
It is prepared by the fermentation of concentrated milk using a starter culture containing both $Lactobacillus$ $bulgaricus$ and $Streptococcus$ $thermophilus$.
This process is typically carried out at a temperature range of $40-46^{\circ}C$ for approximately $4$ hours.

(B) Raw cheese or unripened cheese is commonly known as cottage cheese.
It is produced by the coagulation of milk protein,casein,and is consumed without undergoing a ripening or aging process.

(C) Cheese and yoghurt are nutritious milk products formed by the process of fermentation.
In this process,specific microorganisms (such as $Lactobacillus$ for yoghurt) convert lactose sugar present in milk into lactic acid,which coagulates the milk proteins to form the final product.

(D) Sodium chloride $(NaCl)$ is added during the cheese-making process for several reasons:
$1$. It acts as a preservative by inhibiting the growth of undesirable microorganisms.
$2$. It helps in controlling the moisture content of the cheese,which affects its texture and shelf life.
$3$. It significantly enhances the flavour of the cheese.
Therefore,it serves both the purpose of controlling moisture and providing flavour.

(D) The correct answer is $(d)$.
$Acetobacter$ $aceti$ is a bacterium used in the industrial production of vinegar (acetic acid) from ethanol.
In contrast,yoghurt production typically involves the fermentation of milk by lactic acid bacteria such as $Streptococcus$ $thermophilus$ and $Lactobacillus$ $bulgaricus$.

(B) $Streptococcus \text{ } thermophilus$ and $Lactobacillus \text{ } bulgaricus$ are used in the production of yoghurt.
These bacteria ferment the lactose present in milk into lactic acid.
The process involves curdling milk at a temperature of $40-46^{\circ}C$ for approximately four hours to achieve the desired texture and acidity.

(D) The conversion of milk into curd is a biological process carried out by Lactic Acid Bacteria $(LAB)$ such as $Lactobacillus$.
These bacteria grow in milk and convert it into curd by producing acids that coagulate and partially digest the milk proteins $(casein)$.
This process also improves the nutritional quality of the curd by increasing the content of Vitamin $B_{12}$.

(D) Cheeses are diverse food products that are typically classified based on several characteristics.
These characteristics include their texture (soft,semi-hard,or hard),their distinct flavour profiles,and their colour,which can vary depending on the source of milk and the ripening process.
Therefore,all the mentioned factors are used in the classification of cheeses.

(D) Cheese is produced by the coagulation of milk proteins (casein).
This process involves the use of specific lactic acid bacteria $(LAB)$ such as $Streptococcus$ $lactis$,$Streptococcus$ $cremoris$,$Leuconostoc$ $citrovorum$,and various species of $Lactobacillus$.
These bacteria ferment the lactose in milk into lactic acid,which helps in curdling the milk to form cheese.
Therefore,the correct answer is $D$.

(A) $Saccharomyces$ $cerevisiae$, commonly known as brewer's yeast or baker's yeast, is used in the baking industry.
During the process of bread making, the yeast ferments the sugars present in the dough.
This fermentation process releases $CO_2$ and ethanol.
The $CO_2$ gas gets trapped in the dough, causing it to rise and giving the bread a soft and porous texture.

(D) The dough becomes soft and spongy due to the process of $Fermentation$ carried out by microbes like yeast ($Saccharomyces$ $cerevisiae$).
During $Fermentation$,these microbes break down sugars present in the dough and release $CO_2$ gas as a byproduct.
The trapped $CO_2$ gas bubbles within the dough cause it to rise,making it soft and spongy.

(C) Streptococcus species,such as $Streptococcus$ $thermophilus$,are lactic acid bacteria $(LAB)$ that play a crucial role in the dairy industry.
These bacteria are primarily used in the production of various types of cheese by fermenting lactose into lactic acid,which helps in the coagulation of milk proteins (casein) to form curd.

(B) Selected strains of $Saccharomyces$ are used as Baker's yeast.
It is added to flour during the kneading process.
Yeast secretes enzymes like amylase (which converts starch to maltose),maltase (which converts maltose to glucose),and zymase (which converts glucose into ethyl alcohol and $CO_2$).
The production of $CO_2$ gas causes the dough to swell or rise (leavening).
When the leavened dough is baked,both the alcohol and $CO_2$ evaporate,leaving behind a soft and porous structure in the bread.

(B) The primary ingredients for traditional South Indian dishes such as idli and dosa are rice and $Black \ gram$ ($Phaseolus \ mungo$ or $Vigna \ mungo$). The batter is prepared by fermenting a mixture of rice and de-husked black gram, which provides the necessary protein and texture for the fermentation process.

(A) The production of bread involves the process of fermentation.
Baker's yeast,scientifically known as $Saccharomyces$ $cerevisiae$,is used for this purpose.
During fermentation,the yeast breaks down sugars present in the dough into ethanol and $CO_2$.
The release of $CO_2$ gas causes the dough to rise and creates pores,making the bread soft and porous.

(B) The process described is known as Pasteurization. It involves heating milk to a specific temperature (usually $62.8^{\circ}C$ for $30$ minutes or $71.7^{\circ}C$ for $15$ seconds) to kill harmful bacteria and pathogens, followed by rapid cooling to prevent the growth of remaining microorganisms. This process extends the shelf life of milk without significantly altering its nutritional value or taste.

(B) The production of dairy products such as cheese and yogurt involves the process of fermentation. In the case of yogurt,lactic acid bacteria $(LAB)$ such as Lactobacillus grow in milk and convert it into curd or yogurt by producing acids that coagulate and partially digest the milk proteins. Similarly,different varieties of cheese are produced by the fermentation of milk by specific microorganisms.

(D) The conversion of milk into curd is primarily carried out by Lactic Acid Bacteria $(LAB)$, such as Lactobacillus species.
These bacteria grow in milk and produce acids that coagulate and partially digest the milk proteins $(casein)$.
None of the options provided ($Acetobacter aceti$, $Bacillus megatherium$, $Xanthomonas citri$) are responsible for this process.
$Acetobacter aceti$ is used for the production of acetic acid, $Bacillus megatherium$ is a soil bacterium, and $Xanthomonas citri$ causes citrus canker.
Therefore, the correct answer is $D$.

(D) Microorganisms like $Lactobacillus$ and others commonly called Lactic Acid Bacteria $(LAB)$ grow in milk and convert it into curd.
During growth, the $LAB$ produce acids that coagulate and partially digest the milk proteins.
$Lactobacillus$ $acidophilus$ is a well-known species of $LAB$ used in the fermentation of milk into curd.

(A) Swiss cheese is produced by the bacterium $Propionibacterium \text{ } shermanii$.
This bacterium produces a large amount of $CO_2$ during the fermentation process, which creates the characteristic large holes found in Swiss cheese.

(D) Cheese and curd are produced through the process of fermentation. In the case of curd,microorganisms like $Lactic$ $Acid$ $Bacteria$ $(LAB)$ grow in milk and convert it into curd by producing acids that coagulate and partially digest the milk proteins. Similarly,different varieties of cheese are produced by the fermentation of milk using specific microorganisms.

(B) The production of bread involves the use of $Saccharomyces$ $cerevisiae$,which is commonly known as baker's yeast.
During the process of bread making,the yeast ferments the sugars present in the dough.
This fermentation process releases $CO_2$ and ethanol.
The $CO_2$ gas gets trapped in the dough,causing it to rise and giving the bread a soft and porous texture.

(B) Lactic Acid Bacteria $(LAB)$,such as Lactobacillus,grow in milk and convert it into curd. During this process,they produce acids that coagulate and partially digest the milk proteins. Furthermore,$LAB$ play a significant role in improving the nutritional quality of curd by increasing the content of Vitamin $B_{12}$.

(A) The production of bread involves the process of fermentation.
During this process,the dough is fermented using baker's yeast,scientifically known as $Saccharomyces$ $cerevisiae$.
As the yeast cells metabolize the sugars present in the dough,they release $CO_2$ gas and ethanol as byproducts.
The trapped $CO_2$ gas causes the dough to rise,giving the bread its characteristic porous and soft texture.

(B) Curd is produced by the action of Lactic Acid Bacteria $(LAB)$ such as $Lactobacillus$ species on milk.
$Streptococcus$ $thermophilus$ and $Lactobacillus$ $bulgaricus$ are standard starter cultures used in the production of yogurt and curd.
$Escherichia$ $coli$ and $Salmonella$ $typhi$ are pathogenic bacteria and are not used in food production.
$Rhizobium$ and $Nitrosomonas$ are nitrogen-fixing and nitrifying bacteria,respectively,and are not used in curd production.
$Bacillus$ $subtilis$ and $Clostridium$ $botulinum$ are not used in curd production; in fact,$Clostridium$ $botulinum$ is a dangerous pathogen.
Since the question asks which is 'not used',options $B$,$C$,and $D$ all contain organisms that are not used in curd production. However,in standard competitive biology questions of this type,the intended answer is usually the one containing non-dairy,non-food-grade,or pathogenic organisms. Given the options,$B$ (pathogens),$C$ (soil bacteria),and $D$ (pathogens/soil bacteria) are all 'not used'. If this is a single-choice question,it is technically flawed as multiple options are correct.

(C) The dough used for making foods such as dosa and idli is fermented by bacteria. During the fermentation process,these microorganisms perform anaerobic respiration. As a result of this metabolic activity,$CO_2$ gas is released. The trapping of this $CO_2$ gas within the dough causes it to puff up or rise,giving it a soft and porous texture.

(B) Lactobacillus bacteria are beneficial microorganisms found in curd and other fermented dairy products. When consumed,they play a significant role in checking disease-causing microbes in our stomach and digestive tract,thereby promoting gut health.

(A) Microorganisms such as $Lactobacillus$ and others commonly called Lactic Acid Bacteria $(LAB)$ grow in milk and convert it into curd.
During growth,the $LAB$ produce acids that coagulate and partially digest the milk proteins.
This process increases the nutritional quality of curd by increasing vitamin $B_{12}$ content.

(C) The preparation of pickles involves the fermentation of fruits and vegetables by various lactic acid bacteria $(LAB)$,such as species of $Lactobacillus$.
During this process,these bacteria convert carbohydrates present in the fruits into lactic acid.
This lactic acid lowers the $pH$ of the medium,which acts as a natural preservative and prevents the growth of spoilage-causing microorganisms,thereby giving pickles their characteristic sour taste and shelf life.

(A) Buttermilk contains $LAB$ (Lactic Acid Bacteria) such as Lactobacillus.
These bacteria are beneficial as they play a significant role in checking disease-causing microbes in the stomach and digestive tract.
Therefore,consuming buttermilk after a meal is considered beneficial for gut health.
Both the assertion and the reason are true,and the reason correctly explains why buttermilk is beneficial.

(C) $1$. $LAB$ (Lactic Acid Bacteria) converts lactose in milk into lactic acid,which coagulates and partially digests milk proteins,forming curd. This is a correct match.
$2$. Toddy is a traditional drink made by fermenting sap from palms. This is a correct match.
$3$. Silage is produced by the fermentation of green plant tissues (like corn or grass) to preserve them as animal feed. It is not specifically a process for extracting plant proteins. This is the mismatched pair.
$4$. Pickles are produced by the fermentation of sour fruits and vegetables. This is a correct match.

(B) Toddy is a traditional drink of some parts of southern India. It is made by fermenting sap from palms. The fermentation process is carried out by naturally occurring yeasts present in the sap.

(D) The production of cheese involves two main processes: souring and ripening.
$1$. Souring: Microorganisms like $Lactobacillus$ are used to convert lactose in milk into lactic acid,which causes the milk to curdle and become sour.
$2$. Ripening: Different types of microorganisms (such as $Penicillium$ $roqueforti$ or $Propionibacterium$ $sharmanii$) are used to provide specific textures,flavors,and aromas to the cheese during the aging or ripening process.
Therefore,microbes are essential for both souring and ripening in cheese production.

(A) Baker's yeast is scientifically known as $Saccharomyces \ cerevisiae$.
It is used in the baking industry for the fermentation of dough.
During this process,the yeast releases $CO_2$ gas,which causes the bread dough to rise,making it soft and porous.

(C) Toddy is a traditional drink made from the sap of palms. The sap is collected and left to undergo natural fermentation by yeasts and bacteria present in the environment. During this process,the sugars in the sap are converted into alcohol and carbon dioxide. Therefore,fermentation is the correct process.

(B) $LAB$ stands for Lactic Acid Bacteria.
These bacteria grow in milk and convert it into curd.
During this process,$LAB$ produces acids that coagulate and partially digest the milk proteins,specifically casein.
This process improves the nutritional quality of milk by increasing the content of Vitamin $B_{12}$.

(D) Lactobacillus bacteria,commonly known as Lactic Acid Bacteria $(LAB)$,grow in milk and convert it into curd. During this process,they produce acids that coagulate and partially digest the milk proteins. $A$ very important benefit of this process is that it significantly improves the nutritional quality of milk by increasing the content of Vitamin $B_{12}$.

(A) The dough used for making bread is fermented using baker's yeast,scientifically known as $Saccharomyces \ cerevisiae$.
During the process of fermentation,the yeast cells break down sugars present in the dough into ethanol and $CO_2$.
The release of $CO_2$ gas during this process causes the dough to rise,creating air pockets that make the bread soft and porous.