2019年化学周 - Food Chemistry

What is food chemistry?

Food chemistry is the science that deals with the chemical composition of foods, with chemical structure and properties of food constituents, and with chemical changes food undergoes during processing and storage.

History of food chemistry

The scientific approach to food and nutrition arose with attention to agricultural chemistry in the works of J. G. Wallerius, Humphry Davy, and others. For example, Davy published Elements of Agricultural Chemistry, in a Course of Lectures for the Board of Agriculture (1813) in the United Kingdom which would serve as a foundation for the profession worldwide, going into a fifth edition. Earlier work included that by Carl Wilhelm Scheele who isolated malic acid from apples in 1785.

In 1874 the Society of Public Analysts was formed, with the aim of applying analytical methods to the benefit of the public. Its early experiments were based on bread, milk and wine.

It was also out of concern for the quality of the food supply, mainly food adulteration and contamination issues that would first stem from intentional contamination to later with chemical food additives by the 1950s. The development of colleges and universities worldwide, most notably in the United States would expand food chemistry as well with research of the dietary substances, most notably the Single-grain experiment during 1907-11. Additional research by Harvey W. Wiley at the United States Department of Agriculture during the late 19th century would play a key factor in the creation of the United States Food and Drug Administration in 1906. The American Chemical Society would establish their Agricultural and Food Chemistry Division in 1908 while the Institute of Food Technologists would establish their Food Chemistry Division in 1995.

Food Chemistry Concepts

Food chemistry concepts are often drawn from rheology, theories of transport phenomena, physical and chemical thermodynamics, chemical bonds and interaction forces, quantum mechanics and reaction kinetics, biopolymer science, colloidal interactions, nucleation, glass transitions and freezing/disordered or noncrystalline solids, and thus has Food Physical Chemistry as a foundation area.

Importance of Food Chemistry

Through food chemistry we can understand a lot about the foods we eat. Here are a few ways that food scientists may use food chemistry:

- To understand the nutritional values of food. For example, are apples a healthy food to eat?

- To make new foods, like snacks, yoghurt, gum, ice cream, cereal, soft drinks, juices, and more.

- To determine how long food may last before it spoils. For example, how long will a loaf of bread last?

- To see how different food chemicals interact with each other. For example, what happens when you combine oil and vinegar?

Tainted Food

Any food made unfit for consumption by the presence of a hazardous pathogen or chemical.

Well-known tainted food includes but not limited to:

Melamine Milk

In 2008 six babes were killed and 300,000 were left sickened after consuming infant formula contaminated with the industrial chemical melamine. The scandal, which was hushed up for several months to avoid embarrassment during the Olympic Games, caused outrage in China and smashed public confidence in the government and its ability to regulate the food industry.

Toxic bean sprouts

Police in the northeastern city of Shenyang seized 40 tons of bean sprouts in April 2011. The tainted vegetables had been treated with sodium nitrite and urea, as well as antibiotics and a plant hormone called 6-benzyladenine. The chemicals were used to make them grow faster and look ‘shinier’ in the market stalls. 12 people were arrested.

Pesticide-drenched ‘yard-long’ beans

More than 3.5 tons of “yard-long” green beans contaminated with the banned pesticide isocarbophos, were destroyed after being discovered on sale in the central city of Wuhan in March 2010. The beans had come from the southern city of Sanya, and allegations of another attempted cover-up followed after the Sanya agricultural law enforcement bureau said it was “inconsiderate” of Wuhan authorities to publicise the case.

Leather milk

In February 2011 reports emerged of another milk contamination scandal, this time using leather-hydrolyzed protein which, like melamine, appears to boost the protein-content of milk, thereby enhancing its value. The problem had been detected as early as March 2009 reported the official China Daily newspaper reported Friday. China announced this month it was closing almost half of its dairies in a bid to clean up the industry.

‘Aluminium’ dumplings

After reports that much of China’s rice crop was contaminated with heavy metals, health authorities in Shenzhen, southern China tested 696 samples of food made with flour, including dumplings and steamed buns. Nearly one third (28pc) were found to have levels of aluminium above national standards, the Shenzhen Standard reported. The contamination was blamed on excessive use of baking powder containing the metal.

Glow-in-the-dark pork

Reports and photographs surfaced last month showing pork that glowed an eerie, iridescent blue when the kitchen lights were turned off. Online users dubbed it “Avatar” meat and remained sceptical despite reassurances from the Shanghai Health Supervision Department which said the pork that has been contaminated by a phosphorescent bacteria and was still safe to eat if well-cooked.

‘Lean meat powder’ pork

China has fought a long-running battle with the use of the steroid clenbuterol in pork production. Known as ‘lean meat powder’, it can cause dizziness, heart palpitations, diarrhoea and profuse sweating. The most recent case occurred last March in a stock market-listed pork producer, but China has acknowledged 18 outbreaks of food-related clenbuterol poisoning between 1998 and 2007, according to a report on the Shanghai Food Safety website.

Toxic takeaway boxes

In April 2010 more than 7m toxic disposable food containers were seized in the eastern province of Jiangxi. Although banned in 1999, the foam-boxes are still in widespread use in China, releasing toxic elements when warmed by food. The chemicals have the potential to damage livers, kidneys and reproductive organs.

‘Sewer’ oil

An undercover investigation by a professor from Wuhan Polytechnic University in March 2010 estimated that one in 10 of all meals in China were cooked using recycled oil often scavenged from the drains beneath restaurants. The State Food and Drug Administration issued a nationwide emergency ordering an investigation into the scandal of the so-called ‘sewer’ oil, which further dented public confidence in the food industry.

‘Cadmium’ rice

Research published in February claimed that up to 10 per cent of rice sold in China was contaminated with heavy metals, including cadmium. Data collected by Nanjing Agricultural University found that the problem was most acute in Southern provinces, wherein some areas 60 per cent of samples were contaminated, some with up to five times the legal limit.

Back in Malaysia, we’ve heard a lot of rumours where hawkers added plastic material when frying foods to make the crispiness lasts longer. However, is it true though?

The Plastic In Frying Oil Hoax Debunked

Many people love eating fried foods. We batter all sorts of things and fry them – fish, chicken, pork, bananas, yam, sausages, anchovies… even Oreos, Twinkies and ice-cream! Of course, it’s not healthy to eat them all the time, but we sure love them!

If the health risks are not enough to spoil your appetite, there are the repeated accusations that many vendors add plastic to their frying oil to make their fried treats stay crispy. But just how true is it? Let’s find out!

Plastic-Coated Fried Bananas???

There are many claims of vendors adding plastic to the frying oil they use. They are usually short and told from the first-person perspective, making it look like your friend (who sent it) actually witnessed it. But when you query the sender, they will say that they were just forwarding what they received from their friends.

Here is a particularly detailed write-up from around 2011. For those who do not understand Malay, “pisang goreng” is fried banana in Malay.

PISANG GORENG WILL MAKE YOU SICK

This is a true story (from my friend). Mum said my uncle saw it in Tunjang (Kedah) and the pasar malam in Titi Chai Kangar (Perlis) where goreng pisang was sold in the afternoons. The hawker added a plastic drinking straw into a wok of hot oil and let it melt completely before he started to fry some bananas in the bubbling oil. This is why some fried bananas and ubi are so crispy… for hours…!!

My uncle asked the hawker about this, but the hawker did not answer him. When my uncle told my mum about this, they realised this is how the hawkers ensure that fried food stays crispy for their customers. My mum said that in Thailand, they do the same thing to keep fried ikan bilis and fried onions crispy, even if left in the open for hours!!

Another time, I was with my family in Cameron Highlands. It was 3:00 pm and we were hanging around the market area, where there were several hawker stalls. At one of them, there was a big wok of boiling oil with an empty plastic bottle floating in it and slowly melting.

At first I thought it had fallen into the oil accidentally, but then I saw a little girl, about 7-years old, holding a pair of chopsticks and stirring the bottle around in the hot oil. I realised, Oh my God… these people were using melted plastic to fry food, so that the fried snacks would not turn soft when it cooled down later.

Please forward to all your friends… DO NOT EAT CRISPY FRIED SNACKS from the hawkers!! Even if you don’t see them melting the plastic in oil, they might have added the plastic a few hours before. After all, they keep the black oil for next day’s frying as well, to save cost on cooking oil.

Now, let us debunk this fried hoax once and for all! As usual, we will dissect the hoax logically, before checking its scientific viability.

Pictures Or It Didn’t Happen

Ever since the first iPhone was launched in 2007, smartphones have been all the rage. They have also allowed us to snap photos and take video clips of everything that catches our eyes. Whether it’s the price tag of something we want to buy or an incident we happen to witness. That’s why the Internet is full of “citizen reporters” posting their pictures and videos on social media. Yet, none of these claims is ever backed by photos or videos of the perpetrators. So many different claims of fried food vendors adding plastic to their frying oil but not a single photo? How is that possible? As they say – pictures, or it didn’t happen!

Why Would Anyone Do It Publicly?

The fried food vendors are always described as openly adding plastic straws or bottles to their frying oil, and letting them melt before they start frying their delicious treats. Now, put yourself in their shoes, and ask yourself – would you do it in public? Of course, not! Who in the right mind would be so stupid as to add inedible plastic to their frying oil in full view of their customers? Who would buy their fried foods after witnessing such a travesty???

Fool Me Twice?

Many of us have purchased fried foods all our lives. Have you ever witnessed them adding plastic to their frying oil?  In fact, none of your family and friends will admit that they have ever seen anyone do it. Yet, this writer and his uncle have personally seen two vendors in two different locations doing it. Coincidence? I think NOT.

No One Reported The Vendors?

What would YOU do if you witness such an act? Would you just ignore it and go about your business? Perhaps wait until you are back in the comfort of your home before you write a warning email to their family and friends? Or post about it on social media?

No. Most, if not all, of us would at least snap photos of the vendors and report them to the police and the health authorities. Many of us would probably rebuke the vendors, and demand that they stop doing it immediately!

Why didn’t the writer of that email (who seemed to be, oh, so concerned about well being) report the vendor he witnessed to the authorities? Why didn’t anyone else who saw it happen, for the matter?

The simple answer is – because it didn’t happen. That’s why there has never been a police report or even a news report about such incidences.

Plastic Stinks When You Melt Or Burn Them

Many of us have accidentally burned or melted plastic. You will recall how they STINK when we melt or burn them. So you can imagine just how “fragrant” the oil would smell if someone actually melted plastic in it.

Can The Frying Oil Even Melt Plastic Bottles?

The writer claims to have personally witnessed a plastic bottle melting in the frying oil. But is that possible?

Cooking oil and bottled water are stored in plastic bottles made from PET (Polyethylene terephthalate). PET melts at 260°C (500°F). On the other hand, palm oil, which is the most common frying oil used in such foods have a smoking point of just 232°C / 450°F.

In other words, the frying oil will break down and start smoking before the plastic bottle even begins to melt!

The only cooking oils that are stable enough above 260°C are refined safflower oil and avocado oil. They are the only cooking oils that are remotely capable of melting plastic bottles. Needless to say, they are both much harder to find and A LOT more expensive than palm oil.

What About Melting Plastic Straws In Frying Oil?

Most drinking straws are made of polypropylene, which has a melting point of 130 to 171 °C (266 to 340 °F). So it is possible to melt them in frying oil.

But guess what – the melted plastic won’t actually dissolve in the oil, which is what most people expect. Instead, it just becomes a misshapen clump of soft plastic.

Chewing On A Soft Dildo

Even if you go to all the trouble and expense of actually melting a plastic bottle in safflower/avocado oil, and successfully coat a banana in the molten plastic, you will end up with an inedible plastic-coated banana.

The plastic coat will be hard to chew on. Try chewing on a plastic bag. If that’s not much fun, then you can imagine how it feels to chew on a plastic-coated banana. You will probably feel like you are chewing on a soft dildo… LOL!

Waterproof Food That Won’t Spoil

Plastic-coated fried foods, if they do actually exist, will be quite easy to spot. They will be waterproof and won’t spoil even if you leave them in the open air for many days.

Plastic Cannot Be Digested

Plastic cannot be absorbed or digested by our body. So these plastic-coated fried foods, if they do exist, will pass through our gastrointestinal system intact. If you plastic-coat anchovies, they will pass out in your stool in pristine condition! The only danger of swallowing these plastic-coated food items is that they may cause intestinal obstruction. That’s why turtles die when they chew on plastic bags.