Chemistry of Food

This blog post may seem different from other posts because there is no hands-on session due to unforeseen circumstances but I am going to share about the Future of Food. What does this phrase actually mean? Its definition will vary but in a nutshell, it is how food will evolve and change over the next few decades but we as consumers have a large role in determining this path that the evolution takes. Innovation and technology might lead to us to become more conscious about our own food consumption. This will no doubt stretch the boundaries of the food industry as producers of food will continue to come with new innovations to create food products that are catered to our needs.

For this session of workshop, 4 articles were chosen: The Meat of Affliction, Recent development in 3D food printing, Planting seeds for the future of food and Climate change and Food Security. The reading that I had chosen is Climate change and Food Security which mainly discusses the current and future measures to increase the global food security. Food security exists when all people, at all times have the physical, social and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy lifestyle. The discussion of the article generally revolves around need to increase the accessibility to food for people worldwide as there are still 821 million people in the world who are still suffering from famine. In contrast, there are more than 2 billion people who are obese and this begs the question: Why is there such a disparity in the distribution of food in the world? Another problem arises from the fact that the current global food system is a huge contributor to the total Greenhouse gas (GHG) emissions where by the emissions come from the pre- and post- production activities. There are 4 main pillars of food security consists of availability, access, utilisation and stability.

In order to keep up the increase in demand due to population growth and change in consumption patterns, there are certain measures that are discussed in the various articles to help to mitigate this issue. Firstly, from the article titled as Meat of Affliction, the possibility of the consumption of insects as a staple is being explored by countries as it is an alternative that is readily available. However this solution is the least promising as the idea of eating insects is unheard of among most people worldwide. There are also complications that might arise such as health hazards and other biological problems. Other potential solution to increasing food security is the use of 3D food printing to help increase the availability of food. This idea of 3D printing is not widely accepted but it may be the future of food production because of the many possibilities it may bring. The improvements in food production include mass production and customization (changing the nutrient content and texture/flavour). However there are also problems arising from the application of 3D printing such as high costs and possible psychological barrier which may deter people from trying 3D printed food products. This psychological barrier is likely to be present among the older generation or people who are not educated but I feel that in the long term, people will come to accept 3D printing as a viable food option. A less direct approach to improving food security includes changes to soil and plant management, precision farming and mobile technology. On the other hand, consumers such as ourselves can also do part oursupporting our country’s small business, community planting, adoption of hydro/aero – farming and many more.

Moving on to something more local, Singapore is a small country that has limited resources which means that we have to rely heavily on imported food which makes us more vulnerable to possible changes in the global food system. We also can play a part in tightening Singapore’s food security through the education of the younger generation to eat more healthy and reduce food wastage which are short term measures and possible long term measures can include more research into better genetically modified food products. I believe that in order to ensure that Singapore will not be affected by sudden changes in the global food scene, we should think of solutions which will enable us to be ready to meet at problems head on.

Have you ever wondered how easy is it to make Chocolate Mousse and Ribena Sorbet? It only requires a few key ingredients and you can actually do it in the comforts of your home. Science plays an important role in the creation of chocolate mousse and sorbet whereby there a certain chemical and physical processes which help to give the food dish that unique texture and flavor. In this workshop, we were given a short lecture on Molecular Gastronomy by Dr Linda Sellou before giving the opportunity to hands on in the preparation of the two desserts. Molecular Gastronomy is a sub-discipline of food science which investigates the physical and chemical transformation of ingredients that occur during the cooking process. Cooking and Science were considered very different fields of study in the past, but there has been a growing trend of people who are taking interest in the study of science behind every food dish.

Chocolate Mousse

The preparation of chocolate mousse only uses two main ingredients: Dark chocolate and water. At first I was quite puzzled at the fact that it requires so little ingredients however the process of mixing the chocolate with the water plays an important role in giving the chocolate mousse airy and creamy texture. Each group was given a different kind of dark chocolate where it varied based on the content level of cocoa and sugar. The following picture shows the chocolate brand and type that we got:

The scientific process which plays a key role in the creation of chocolate mousse is known as Emulsion which refers to a dispersion of droplets of one liquid (oil) in another (water) which is not soluble or miscible. Upon mixing, the water and oil separate into two distinct layers and a group of small molecules known as emulsifiers which are present at the water-oil boundary help to bind the 2 phases together. Dark chocolate contains cocoa fat, sugar, cocoa powder, soy lecithin (an emulsifier), and a small amount of water. When hot water is added and the chocolate is melted, an emulsion system is formed. The hot water becomes the continuous phase, and oil (melted cocoa fat) becomes the dispersed phase forming a oil-in-water emulsion. Whisking introduces air cells inside this emulsion, the cocoa fat molecules then move around and coat the air cells. When cooled down over an ice bath, oil molecules solidify into fat crystals hence trapping the air cells permanently. That’s how the chocolate-water mixture turns airy and increases in volume and transforms into the Chocolate Mousse.

However, things didn’t really go out as planned as our whisking session took a long time and yielded no results. After a while, our chocolate-water mixture remain water-like despite putting it in a ice bath. There were two possible reasons: Excess of water added or the type of chocolate used was not suitable. In our attempts to hasten the formation of the fat crystals we tried to add dry ice into the mixture which had significant effect on solidifying the mixture.

After our not-so-successful attempt at making the chocolate mousse, we proceeded to make the Ribena Sorbet. Why use dry ice? Dry Ice and Liquid Nitrogen are the two common cooling agents used in creation of sorbet. Dry ice is in fact solid carbon dioxide which is a around -78.5 degrees celsius. The dry ice was first broken up into small pieces in order to increase the surface area of contact of the dry ice with the ribena syrup. When the dry ice comes into contact with the ribena syrup, heat energy will naturally transfer from a region higher temperature to a region of lower temperature. This phenomenon will result in the cooling of the ribena syrup as the heat is transferred to the dry ice which in turn results in the sublimation of the dry ice (evident in the smoke that is being formed). Hence the ribena syrup is lowered to a temperature where the water present freezes thus forming the sorbet.

Overall the workshop taught me how to better appreciate the science behind cooking as there is much more to cooking than just mixing things together. There are in fact chemical processes behind the scene that help to create the texture and flavour that we all love in our food dishes.

Introduction to Pancakes

Pancake is a very common food item that is sold around the world and it takes on many different forms – from sweet to savoury. It is hard to find a country that does not have pancake or a similar form in their line of delicacies. Everyone likes pancakes and there is a secret behind every recipe of each kind of pancakes. Pancakes have very different forms ranging from thin European Crepe to thick North American ones and many others such as the popular savoury pancake wrapped with leek that is found in Taiwan. The process of making a pancake may seem simple but there are a lot of small details to take note of which may affect the texture and flavour of the pancake.

Today we had the privilege of making our own pancake during the pancake workshop where we had to follow a recipe given by Zi Quan. My group chose to do the western pancake and we use a wide range of different chemicals. The dry ingredients included sugar, flour, salt and baking powder. In a nutshell, flour supplies the proteins which are molecules that contain many amino acids and the sugar supplies simple sugar molecules which will form starch. I always wondered where all the various pastries get their chewy texture? This in fact is the work of the gluten proteins which are simply proteins that do not dissolve in water but form association with water molecules. The addition of eggs and milk into the flour causes the gluten molecules to become more flexible and bind to each other. The resulting batter is then whisked in order to trap carbon dioxide gas which aids in the rising of the pancake dough. Baking powder is often used in order to produce the carbon dioxide gas that is required to rise the dough.

We were provided with necessary ingredients to prepare our own pancake as shown in the picture above. The steps provided in the recipe were easy to follow but we did encounter some problems along the way such as the melting of the butter. However, the problem was easily resolved, and we managed to begin mixing the batter well. We were told that the mixing of the batter was very important because hard mixing will result in the formation of the gluten which will allow the mixture to stand and hence leading to the swelling of the starch and popping of gas bubbles. This ensured that the pancake would have a strong structure with lesser holes. The mixing of the batter was not an easy task because it required constant and strong-arm movement which reminded me not to take household appliances for granted again.

After we managed to achieve as relatively homogenous mixture, we then proceeded to cook the pancake on a pan. The key idea was to heat the pan up to a temperature that was hot enough to allow the batter to turn brown quickly but not too hot such that the batter will set before it has time to spread. Due to the availability of only a small pan, we had the chance to cook many batches of pancake and we took this chance to alter the flavour of the pancake by adding more vanilla extract straight into the batter before cooking it. The aroma and colour of the pancake is apparently the aftereffects of the Milliard reaction whereby the reaction of amino acids and reducing sugars result in a wide range of small molecules that escape into the air, producing an aroma that is similar to that of nuts, bread and coffee. These molecules that are responsible for the aroma is commonly known as melanoidins which are currently studied for their possible antioxidant effects.

It was an overall fun and enriching experience to learn the sciences behind a simple cooking process but this workshop has gave me an opportunity to understand more about the chemical reactions and physical processes that can affect the outcome of the creation of a pancake.

Today i attended a Fermentation workshop hosted by Mr Tan Ding Jie, a research officer who is working at A* Star and his primary research is on Organic Synthesis and Biosynthesis of flavours. Fermentation is a biological process which is carried out by micro-organisms such as Yeast and Bacteria to transform raw materials into popular food products such as Beer, Yoghurt and Kombucha. Fermentation is a process which makes use of microbes (Yeast, Bacteria) to chemically break down substances unlike cooking which is a thermal method.

Fermentation Microbiology of Kombucha

For this workshop, we focused on the inoculated source of microbes which is refer to as SCOBY, short for symbiotic culture of bacteria and yeast which is commonly used in the production of several traditional foods and beverages such as Tempeh, Natto and Miso. There are many types of bacteria such as Lactic Acid Bacteria (LAB) and Acetic Acid Bacteria (AAB). The main bacteria that is used in the fermentation of Kombucha is Acetic Acid Bacteria (AAB), which are obligate aerobes that require oxygen to synthesise the cellulose layer. The other important component of SCOBY is Yeasts which are used in preference to Fungi & Moulds. Fungi and Moulds are avoided in the fermentation process as it is harmful to the human body. For fermentation of Kombucha, a Mixed-Culture is used of bacteria and yeast complemented with two-stage process which incorporates aerobic and anaerobic stages.

Factors that affect Fermentation

There are mainly 2 types of factors: Intrinsic and Extrinsic. Intrinsic factors are often adherent to the a certain batch of fermented product which is hard to predict. These factors include Acidity, Water activity, Nutrient content, Antimicrobial and Biological structures. Extrinsic factors would include Temperature, Relative Humidity, Gaseous Exchange and presence of microbes.

Steps of Kombucha fermentation 

1. Brewing of tea – This steps involves the brewing sweet tea that is used to mix with the starter culture. The tea consists of typically 1% by weight of tea, 7% by weight of sugar. The tea has to be cooled down after brewing so as to ensure that the culture will not get denatured due to high temperatures.
2. Inoculate – Addition of starter culture to the brewed tea and the volume of starter to be added is around 10 – 20% by weight of total kombucha.
3. Ferment – This step takes a few days (5 to 7) and it involves the aerobic fermentation of the kombucha. A material that is porous is used to cover the container containing the kombucha which allows for air to initiate the fermentation process but not any contaminants as this might lead to the formation of mould or fungi.

The picture above shows the initial appearance of the kombucha before primary fermentation. The taste of the kombucha was very sweet and it tasted like ordinary tea.
This photo was taken after 5 days and a white layer of cellulose can be seen on the surface of the tea. The tea retained its very strong aromatic flavour but it also had a a slightly effervescent texture. The layer of cellulose was hard to chew and had little flavour.However comparing with the kombucha served in glass bottle, the one in the glass bottle had a much pleasant flavour which could be largely due to the juice that was added instead of brewed tea.

Health Benefits of Kombucha

Kombucha is traditionally a carbonated drink which is normally brewed with sugar, black or green tea and SCOBY. The drink has been promoted to be a supplement that helps to improve digestion and lower the chances of diabetes. Further research have shown that there are people who strongly advertise Kombucha as being probiotic but this has yet to be 100% scientifically proven. However one thing can be sure which is that the drink can tap into interest in the microbiome, this in turn affects the micobial communities in our gut which will affect our emotional and physical well-being. In conclusion i believe that Kmobucha has much potential into becoming a crucial component of maintaining a healthy body system in humans in the near future.

Coffee is a term relating to the beverage that is an essential part of everyone’s life as it provides the fuel or energy we need to conquer the day’s task. However do we actually know what is coffee and how it is made? We tend to take the process of making coffee for granted because at times we are always on the rush and consumption of the coffee often occurs without us pausing to think about what coffee actually means.

I have had the privilege to take part in a Coffee Theory & Tasting session conducted in NUS by the co-founder of The Coffee Roasters. Swee Heng. The Coffee Roasters which was founded in Feb 2014 has now grown into one of the highest volume specialty cafes in Singapore. As an introduction to the workshop, Swee Heng kindly presented as with 2 cups of coffee and urged us to describe the taste and aroma that we can detect and how it varies from each cup.

As seen in the photo above, the 2 cups seem visually the same based on colour and texture, however drinking and smelling the 2 cups, there was a distinct difference in the 2 types of coffee. The coffee in the cup labelled C had a more Herbal/ Hazelnut taste with a slight sour aroma whereas the coffee in the cup labelled E has a bitter aroma with a sweeter and fruity taste to it. Cup C coffee is brewed using Coloumbian Coffee beans whereas Cup E coffee is brewed using Utopian coffee beans. This small tasting session has demonstrated the fact that the compounds found in the coffee beans remind us of certain food items. There are generally three main types of coffee beans in the world: Arabica, Robusta and Librica. Such coffee beans are often grow in countries along the region known as the ‘Coffee Belt’ such as Colombia (South America), Ethiopia (Africa) and Vietnam (Asia Pacific).

Coffee Myths and Facts

Another interesting takeaway from the workshop was finally being able to understand why there are so many different types of coffee found on the Starbucks menu. In a nutshell, there are mainly two categories of coffee: Black and White coffee. Starting off with black coffee which consists of Americano and Long Black which to me seems like the exact same drink. In actual fact, there are made with espresso but differ in the preparation process. The intriguing thing to me was that a simple reverse of order in the addition of hot water to espresso could result in two types of coffee which may look the same but taste slightly different. Moving on to white coffee which is the type of coffee that I normally go for, there are in fact three types: Cappuccino, Flat white and Latte. These three coffees vary largely because of the ratio of foam to coffee. I have been told that people tend to stick to one kind of white coffee but after attending this workshop, I am more interested in trying out other white coffees and comparing their texture and flavour.

Espresso and Extraction Theory

The ideal taste coffee among people tends to be something along the line of sweet, nice mouth feel and good after taste, all these characteristics can be achieved through certain modifications in the extraction process. The definition of extraction can be said to be everything that the water takes from coffee. An important component of the extraction process is the Brew Ratio whereby it is essentially the ratio of the mass of coffee grounds to that of the liquid espresso in the cup. The variation of Brew ratio will result in the the difference in the amount of liquid coffee produced at the end which affects the flavour and texture of the coffee.  Another factor that affects extraction process is the Grind Size of the coffee grounds extraction efficiency of the coffee beans. There is no ideal grind size to use as it varies based on the brewing method because not all methods require high extraction of the coffee beans. Other factors also include: Brew time (Duration of coffee immersion with water), Brew temperature ( Amount of thermal energy supplied to the coffee grounds), Pressure ( Increased pressure increases extraction but no change observed at high pressures) and Water hardness (Presence of ions in the water)

Compounds present in coffee grounds

Extraction of coffee beans can either be over-extraction or under-extraction which results in the variation in the compounds that are extracted from the coffee beans. Coffee beans tend to contain compounds namely: Caffeine, Acids, Lipids (Fats), Sugars and Carbohydrates starting with the most soluble. The final taste of the coffee is dependent on the degree of extraction which affects the compounds that will be present in the coffee at the end. This is why coffee that is brewed at local coffee shops tend to be more bitter and dry is due to the common practices among drink stall owners to over-extract in order to get as much out of the coffee grounds. But this will result in the carbohydrates (including plant fibers) that will get extracted which give local coffee the distinct bitterness.

Hi all, I am Leong Zhi Sheng, a year 3 chemistry major specializing in Environment and Energy and this is my blog which will serve as a platform for me to share with everyone things that I have learnt in the workshops and online videos in this module. This module comprises of mainly 5 workshops covering various subjects such as Coffee, Fermentation of Kombucha, Pancake, Ice cream & Chocolate and Molecular Gastronomy. The module’s contents also include many online videos which help students to better understand relevant Chemistry and Biological jargon.

As an introduction to DMS1401CM, the concepts and basic knowledge of Food is essential in ensuring that we are better prepared when we attend the various workshops. For week 1 and 2, the main reading that I focused on can be found in the book titled “On Food and Cooking, the science and lore of the kitchen”. The topic that I plan to share today is about the four basic food molecules which are Water, Fats, Carbohydrates and Proteins. Water is the most prominent molecule present not only in food but also as a large percentage of the human body (almost 60% by weight). Water plays an important role in giving our food its flavour, texture, structure and stability. Water serves as a medium in the various food processes and it dissolves other substances very well due to the ease of the forming of hydrogen bonds which leads to molecular separation. Moving on to the next food molecule which is known as Lipids which are essentially Fats or Oils. This food molecule plays an important role in ensuring that many foods have their smooth and pleasant texture through a process known as tenderizing which breaks down the structure of foods. Fats and Oils act as a medium which allows us to heat up the food above the boiling point of water in order to create a dry and crispy surface of foods which we know as Fried foods. Fats can be also categorized as saturated or unsaturated which can be differentiated by the molecular structure of the lipid (presence of Carbon-Carbon double bond). Many different forms of fats are present in our body and they are formed through chemical processes such as hydrogenation or twisting of the C=C bond. Carbohydrates are basically the simple sugars or starch have the main role of storing chemical energy in living things and serve as the basis of skeletal structure stability for plants. Carbohydrates have various forms such as Simple sugar, Oligosaccharides and Polysaccharides (starch, glycogen, cellulose, plant gums). Simple sugars and Starch are the most common forms of carbohydrates but they have very different roles. Sugars are very important nutrients as our body are biologically designed to sense the presence of sugars which is characterized by sweetness. The last food molecule which is known as Proteins which are considered to unpredictable and the hardest to understand. Proteins are very susceptible to changes such as addition of heat, exposure to air and reaction with acids or bases. Proteins are made up of smaller molecular units known as Amino acids but in combination with other amino acids, they form macromolecules which make up RNA and DNA. Proteins are at the heart of all organic activity, growth and movement hence cooking allows us to take control the proteins dynamic nature to create new structures which can lead to a larger variety of food.

These four food molecules are just the tip of the iceberg and there are many more things to discover about the science of food which will be shared more on my blog in the coming weeks.

 

 

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