Curious Cook: Banana leaf, plastic and other musings

A leaf out of nostalgias book ... a banana leaf rice meal at Acha Curry once created many happy memories, and has now become comfort food.

Some years ago, I took a visitor from Europe to eat at Money’s Corner in Sentral, Kuala Lumpur. Being from the United Kingdom, my guest had expressed a preference for an Indian meal and I thought that a good banana leaf Indian lunch would be a great idea.

Things were sailing smoothly when the banana leaves were plopped on the table but it went downhill rapidly when the rice was ladled on top of the leaves. My guest had expected a plate on top of the leaf and expressed horror at eating food from such an “unhygienic” platform – and my explanations about the cleanliness of the banana leaves did nothing to change matters.

In the end, I had to ask for a plate (which Moorthy’s Mathai Indian Rice gracefully provided without complaint) and everything ended up much better after that.

I’m not sure why that memory about banana leaves popped up again recently, but it may be something to do with plastics, or more specifically, food containers made with plastics.

Lots of you may be aware that we should avoid using plastic tableware or containers made with BPA – but actually, if you consider BPA a naughty chemical, then there may be other more worrying items in our kitchens.

The banana leaf

But first, let’s clear up the known facts about banana leaves. Bananas are herbaceous plants in the genus Musa – and the most populous species in South East Asia (and Malay-sia) is probably musa acuminata. Bananas are also one of the earliest plants to be domesticated, probably around 8,000BC or earlier.

Many people would have heard that banana leaves have some miracle antibacterial and antifungal properties that somehow makes them a wonderful natural platform on which to serve food. There is some truth in this, although studies have shown that banana leaves from musa acuminata are not effective against some common bugs such as E. Coli, K. pneumoneae and Bacillus subtilis.

The leaf is more than a plate - it infuses a subtle fragrance to the food served on it, like roti canai.

However, their leaves have demonstrated better antibacterial properties against other common bacteria such as P. aeruginosa, E. aerogenes, P. mirabilis, S. flexneri, Citrobacter, E. faecalis and S. aureus. The leaves are also quite effective against fungi such as Aspergillus terreus and Penicillium solitum.

As a side note, if I wanted to be even safer, and if it were possible, I would keep food inside the skin of the banana fruit itself for the peel has significantly better antibacterial properties than the leaves. So basically, it is true – it is probably mildly safer to eat on a banana leaf than on a plastic dish.

Plastics and our food

This returns us to the subject of plastics again. The problem with plastics which we hear a lot of these days is usually to do with BPA (or bisphenol A – or even more accurately, 4,4’-dihydroxy-2,2-diphenylpropane).

The word plastic derives from the Greek plastikos, which means something that can be easily shaped or moulded – for example, the toy substance plasticine might spring to mind.

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ALSO READ: Processed meats: WHO says it’s bad

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The base chemical components of the various kinds of commercial plastics are now usually derived from petroleum and BPA comes into the picture during the production of a special kind of plastic known as polycarbonate plastic.

This is a very useful plastic for it is clear, easily coloured and practically unbreakable – and is therefore immensely suitable for making stuff like water bottles, food containers, sports equipment, medical devices, DVDs, plastic pipes, household electronics and even spectacle frames and lenses. BPA is also used to produce the epoxy resin which coats the inside of almost every beverage or food can. So whether you like it or not, it’s pretty certain you would have ingested some food or drink which had been held inside a container made with BPA.

To make it worse, if you’ve ever handled a receipt or printout generated by a thermal paper printer, then the developer compound on the paper is actually BPA in a rather pure form and this can be particularly dangerous as then the BPA can be absorbed through the skin or ingested via unwashed hands after handling thermal paper.

The good news about BPA

Before you get too concerned, there is some good news and there is some bad news. The good news is that BPA is not acutely toxic – it is not a compound that can cause death or diseases in a short time frame even if ingested in larger than normal concentrations. Most of the toxicity evidence against BPA have been detected in experiments where the test subjects were subjected to unrealistically high concentrations of the compound.

Polystyrene boxes are not free of BPA and should not be used for hot foods especially.

Also, BPA from food and drink is metabolised relatively quickly in the liver and gut before it reaches the bloodstream and therefore it has been claimed that it would be unlikely that other organs in a normal healthy body would get exposed to BPA – unless it was from contact with thermal papers (so make sure you wash your hands after handling thermal paper).

BPA has also been in commercial use for a long time, since 1957, so wholesale exposure by the world’s population to BPA has thus far not led to any sizable health issues in the general population which can be conclusively linked to the chemical.

The bad news about BPA

The bad news is that there is pretty solid evidence that BPA can affect the Central Nervous System (CNS) in our bodies. To be precise, BPA messes with the function of a gene called Kcc2 which is involved in the growth of neurons or nerves cells in the brain and spinal cord.

To complicate matters, it seems to affect female neurons rather than male neurons. Exposure to BPA may therefore have a connection to Rett Syndrome, a form of autism found only in girls, though it has to be added that no known statistical study on the BPA link to Rett Syndrome humans is available.

This lack of data from direct experiments based on human exposure to BPA has led to some inferential studies. Since the use of BPA is now already so widespread in the population, some researchers in the US did a study based on the levels of BPA in human urine samples and various diseases and concluded that there may be a link between levels of BPA exposure and cardiovascular problems. However, I have to add that there may be several other factors involved than just BPA so statistically-speaking, this study probably does not carry too much weight.

And the really bad news about BPA

However, there is one other significant item of really bad news. All BPA products leach chemicals which can mimic or disrupt the functions of natural hormones called estrogens. These chemicals are classed as having Estrogenic Activity (EA), which also means that they are endocrine (or hormone) disruptors.

Now this is pretty bad indeed as EA chemicals can cause many adverse health problems at very low doses – perhaps even in doses as small as 1 part in a trillion. The health problems include tumours, birth defects, and mental and physical developmental issues.

Several studies based on normal expected exposure levels to BPA have confirmed that EA chemicals leached from BPA pose quantifiable health risks in test animals and therefore by inference, probably in humans as well. This appears to be supported by a 2011 study (in the journal Pediatrics) which suggested that pregnant women with high levels of BPA in their urine are more likely to have daughters with signs of hyperactivity, anxiety, and depression. Some other effects of BPA detected in animals are abnormal brain development, metabolic disorders, male fertility issues, asthma and intestinal problems.

A new problem?

Paradoxically, what may have created a bigger problem was the American ban in 2012 on the use of BPA for baby feeding bottles. The ban was based on the abovementioned studies which indicated the adverse impact of EA chemicals on foetal development.

This has led to a rather profound consumer scare against BPA and a rush to deliver alternatives to BPA. And it turned out that the best candidate nominated by the chemical industry to replace BPA is BPS (bisphenol S, or 4,4’-sulfonyl-bisphenol). As a result, many of the plastic containers in the shops which are labelled “BPA-free” are now made with BPS or some derivative of BPS.

At this point, I have to let out a little sigh. The use of BPS was chosen primarily because it was claimed that it is more inert than BPA and therefore less likely to leach out chemicals. While it is definitely true that BPS is definitely “BPA-free”, it is also completely certain that BPS also leaches out EA chemicals.

A study by the University of Calgary dosed zebra fish with identical quantities of BPA and BPS and found that the fish dosed with BPA had an abnormal neuronal growth rate of 170% compared to fish in the control group. For fish dosed with BPS, the neuronal growth rate was 240% compared to the control. Hence, the reason for my sigh.

These biodegradable plastic bags, clamshells, plates, bowls and cutlery are made from tapioca-based resin.

The crazy reality is that no biological studies was done beforehand to ensure that BPS would be less of a problem than BPA, so “BPA-free” appears to be just a marketing label to persuade the public to buy a product with probably the same problems as BPA, if not worse.

I won’t venture into the motives behind why the chemical industry chose to inflict BPS on the public (over 80% of Americans now have detectable levels of BPS in their urine, and over 90% have BPA).

To be fair, BPS is still not classified as toxic, and it seems it’s not a legal requirement to check for long-term health issues in plastics used for containers – though one would have thought they would have learnt something from the ban on BPA.

Also, a study by the University of Texas in 2011 came to the sobering conclusion that practically all commercial plastics leach out EA chemicals under various conditions.

And economically speaking, it is probably impossible to replace the use of EA plastics in modern society so we simply have to learn to live with such chemicals in our environment. As such, here is a list of common sense suggestions to avoid EA chemicals in food and drinks for those who may be interested:

1. Use glass, ceramic or stainless steel containers for drinking water or juices.

2. Reduce the amount of canned food and drinks consumed, especially for infants.

3. Don’t microwave food in ANY plastic containers and don’t use roasting bags.

4. Don’t use cling film, especially to wrap or cover hot or warm foods

5. Use glass, porcelain, ceramic or stainless steel cookware for cooking and storing food.

6. If you do have plastic containers, do not store them in areas with exposure to sunlight.

7. Don’t handle any documents or receipts printed on thermal paper. If you have to, then dispose of the paper quickly and wash your hands.

8. Generally, just simply reduce the use of plastics wherever possible.

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UPDATE: On Feb 1, 2016, a reader commented on the article

I refer to the eight “... commonsense suggestions to avoid EA chemicals in food and drinks for those who may be interested” that Chris Chan lists in his article.

No.7 says: “Don’t handle any documents or receipts printed on thermal paper. If you have to, then dispose of the paper quickly and wash your hands.”

Now it may be a coincidence but within two months of that expose on endocrine (or hormone) disruptors BPA/BPS, I noticed something on a supermarket receipt that

I may not have spotted before – please take a look at these pictures.

The back of the thermal paper receipt is marked BPA free - Non Toxic.

The supermarket receipt printed on thermal paper.

My question: Is there any basis for the claim “BPA Free – Non Toxic” printed on the back of the receipt?

Perhaps you might consider a follow-up to Chris Chan’s “musings”. – shaoming WANG

Chris Chan’s reply:

I have seen some of those thermal papers as well, but honestly, the claim of being “BPA free” does not mean very much because they are usually coated with BPS instead, which is just as bad. As both BPA and BPS are not actually toxic, the claim for being “Non-Toxic” is also technically true. For something to be defined as toxic in science means that it induces harmful effects with a single or short-term exposure.

In product labelling conventions, toxic means “Can cause death, eg if swallowed, breathed in or absorbed by skin” but BPA and BPS are not obviously toxic under both definitions – the phenols just mess with the endocrine system so that cancer or ill health becomes more probable later on in life and raises the likelihood that unborn children get some form of damage.

As things stand, saying a paper is “BPA-free” is really unhelpful because it is almost certain that the BPA would have been replaced by BPS, which is just as disruptive of the endocrine system. So please treat “BPA-free” thermal paper with the same caution as BPA-based thermal paper.

I would be much more heartened if the paper is labelled as “phenol-free”. That would be very much safer – and there is a new thermal paper launched only last year which uses ascorbic acid (vitamin C) as the thermal developing agent on paper.

You can read up more on it at the following links:

https://www.pca.state.mn.us/quick-links/green-chemistry-and-design-bpa-thermal-paper

http://www.thermalroll.com/phenol-free-thermal-paper-rolls/

http://www.greenstar.coop/stores/1370-co-op-switches-to-phenol-free-receipt-paper