Food

Food chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods.

To start off, the most basic thing that our body needs to digest food are digestive enzymes. There are 4 types of enzymes- Amylase, Maltase, Protease, Lipase. Along which, starch and amylase belong to a group called Carbohydrates. There are three main types of food groups- carbohydrates, proteins and lipids(fats).

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What are enzymes?

Enzymes are complex proteins that speeds up the rate of chemical reactions. Enzymes remain unchanged at the end of chemical reactions.

Preserved food have food additives added in it. It helps to preserve flavour and builds up its taste and appearance. Additives have been used since the past. Many more additives have been discovered over the past few centuries, and they can be both natural or artificial. They are many harmful addictive present in this world- and most of them are what we consume daily.

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Have you ever wondered why dogs can’t eat chocolate?

Chocolate consists of Theobromine. Theobromine is a mild stimulant, similar in effect to caffeine, which is found in chocolate. This compound is harmless to humans at levels of eating chocolate. It will take us to consume ten kilograms of milk chocolate before we die. However, for cats and dogs, theobromine has a potent effect. Small doses could lead to vomiting and diarrhoea. Only the consumption of 50g of dark chocolate could kill a small dog.

Household cleaning product (stain remover)

Be thankful for the presence of chemistry as it is here to help us remove our stains. Many different molecules are present in stain removers and detergents to help remove grease and dirt, and they have different functions.

Stains can be grouped into several groups: enzymatic, oxidisable, greasy, and particulate. In reality, a stain will have a few components, which may fall into more than one of these categories. As such, stain removers have multi-functions (a mixture of all of the agents), to remove these multi-component stains.

Enzymatic stains are mostly made up of proteins, which includes blood stains and human sweat. Enzymes present in stain remover can be used to break down the protein. Proteases will break down proteins by breaking down the larger molecules into smaller, soluble molecules. Other molecules (fats and starch) that can be broken down by enzymes (lipase and amylase).

Brightly coloured stains is in the oxidisable stain category. These include stains like tea and coffee, as well as red wine. Stain removers contain bleaching agents, most often hydrogen peroxide, which breaks down colour-causing sections of chemical structures, removing the appearance of the stain. The hydrogen peroxide(gas) is usually in the form of sodium percarbonate(solid), which releases hydrogen peroxide when dissolved in water.

However, hydrogen peroxide does not function well at removing stains below 40˚C. It is not an issue if one is washing at or above that temperature, but if you’re washing below, or just wanting to use your stain remover on carpet or furnishings, the hydrogen peroxide needs to get some extra help- an addition of tetraacetylethylenediamine(TAED). TAED reacts with hydrogen peroxide to produce peracetic acid, which makes it a stronger bleaching agent as compared to hydrogen peroxide.

Oils and grease can be broken down by lipase enzymes but they are primarily removed by the use of surfactants. These are commonly long carbon chain compounds with a charged water-soluble ‘head’ and an oil-soluble ‘tail’. Generally, they are either named ‘cationic surfactants’, ‘anionic surfactants’, or ‘nonionic surfactants’ on the stain remover bottle. It refers to the charge on the molecule’s ‘head’. A cationic surfactant has a positive charge, an anionic surfactant a negative charge, while a nonionic surfactant is electrically neutral.

These surfactants remove oil and grease by forming structures called ‘micelles’ around them. The oil-soluble parts of the molecule dissolve in the oil or grease, forming a spherical structure around the oil droplet. The water-soluble parts of the surfactant molecule then stick outwards, which means that that the micelles will be able to dissolve in water, allowing the greasy stain to be removed.

Last but not least, we have particulate stains. There are compounds in the stain remover which are also known as ‘Builders’. These compounds primarily help to soften the water during washes by removing positive metal ions (mainly calcium and magnesium ions) from the water. It is also useful in removing soil stains from clothes, as these stains are often bound to fabrics by calcium ion bridging. Removing the calcium ions therefore helps remove the dirt.

Washing detergents is commonly uses sodium triphosphate as a builder, but due to concerns about its excessive release into the environment, many companies have now swapped it with other agents, such as sodium carbonate or zeolites. Zeolites are crystalline aluminium silicates, inorganic structures that is ready to bond with calcium and magnesium ions. They also possess a number of advantages over other builders, such as inhibiting dye transfer during washes. Generally, builders help improve the cleaning action of other chemicals in the detergent, by preventing cations combining with other charged molecules, such as surfactants. They can also help prevent the redeposition of dirt onto fabrics once it has been removed.

Why do we tear up when chopping onions?

Before harvesting, onions absorb sulphur from the earth. Onions contain amino acid sulfoxides that form sulfenic acids in onion cells. Enzymes and sulfenic acids of the onion cells are kept separately. When cutting an onion, it separates the enzymes. The enzymes then start mixing with each other and produce a propanethiol S-oxide, which is a volatile sulphur compound. The gas emitted reacts with the water of one’s eyes and form sulphuric acid. Sulphuric acid causes burning sensation in eyes. The lachrymal glands in eyes then become irritated and produces tears.

Enzymes : alliinases – found in onion & garlic
Propanethiol S-oxide (C3H6SO) : main chemical compound that causes tears when chopping an onion
Lachrymal glands : an almond-shaped exocrine glands (produce and secrete substances onto an epithelial surface by the way of a channel leading from exocrine glands or organs) , one per eye, that secretes the aqueous layer of the tear film


Ways to avoid having to tear up when cutting an onion

1.Refrigerate the onion before cutting
– by doing so, it freezes the enzymes from mixing with the sulfenic acids & the production of propanethiol S-oxide is stopped.

2.Cook the onion before cutting
– it inactivates the enzyme so there will be no chemical reaction occurring

3.Soak the onion in water before cutting
– the water will absorb the gas of the onion and therefore there will not be any propanethiol S-oxide formed

Fun fact: allium cepa is another name for onions.

To learn more, here’s a short video that summarises the above topic

Cosmetics

Many women use cosmetics to enhance their beauty. However, not many know the chemicals in the cosmetics that could harm their health. Of the many different toxic chemicals in cosmetics, here are 3 types : carcinogens, formaldehyde and nitrosamines. Information below will show the effects of the chemicals on our human body through different kinds of usage of the chemicals other than the application of cosmetics.

CARCINOGENS:
It is a substance that could cause cancer in living tissues. They can be found in things such as cigarettes, deodorants, hair sprays and many other things we use in our everyday life. However, they only contain a very small amount of carcinogens in them.
Some examples of cosmetics that contain carcinogens are Talcum powder and foundations. Talcum powder is found in baby powders. It used for preventing diaper rash, as a deodorant, and for other cosmetic uses. However, some baby powder would have use corn starch instead of talc [Mg3Si4O10(OH)2]. Talc, the main ingredient, is a carcinogen that increases the risk of ovarian cancer. Certain cosmetics brand also contains carcinogens in their lipsticks, eye liner and nail polishes.

FORMALDEHYDE(CH2O):
It is a colourless, flammable gas that is very often used in cosmetics. It a also a type of carcinogen. This gas causes sore throat, burning sensation in eyes, skin irritation, cough and nausea if there is too much breathed in. Formaldehyde help protect cosmetic products against contamination by bacteria during storage and during continuous usage. It is also found in products such as plywood, glues, adhesives, certain insulation materials and cigarette smoke. Prolonged exposure to formaldehyde can cause leukemia and pneumonia.

NITROSAMINES:
This chemical compound is used to manufacture some cosmetics, pesticides and most rubber products. It is also found in processed meat. They are carcinogenic compounds that increases risk of gastric or pancreatic, stomach and colon cancers, diabetes, fatty liver disease and obesity. They are also related to Alzheimer’s disease (progressive mental deterioration that can occur in middle or old age, due to degeneration of the brain) and Parkinson’s disease (a progressive disease of the nervous system). Apart from the harm that nitrosamines could bring to us, there are also benefits. Nitrosamines enhances cardio circulation which improves our circulatory system.

Perfumes

Perfumes are made of a base and a fragrance compound. The base used is commonly alcohol or water. Ethyl alcohol is usually used as it evaporates quickly on the skin.

The main components of perfume consists of a perfume oil, an alcohol, and water.

Perfume oil can be categorised into two different types. A synthetic oil, or a fragrance taken from a natural source. Oils can be extracted from flowers, plants or animals. The oils are split into three parts: The top note, the heart note, and the base note. The top note is what you smell immediately after putting on the perfume. The heart note is what you smell 3-4 hours after applying and it and the base note sticks easily to the skin and can stay for up to eight hours. Chemical equations of the perfume oil depends on where the oil was taken from. The top notes are lighter and have a smaller intermolecular force therefore evaporates first followed by heart note with a slightly bigger intermolecular force and then base note with the biggest intermolecular force