Introduction and Speaker Background
- The talk begins with a disclaimer about the tasters that will be provided to the audience, warning those with food allergies or intolerances not to participate, and introducing the speaker, Dr. Chris Clark, who has a background in physics and has worked in various fields, including science communication, television, and food science consultancy 10s.
- Dr. Chris Clark explains that he has taken a scenic route in his career, starting as a physicist, then working in science communication, television, and food science consultancy, and is now a teacher in Luxembourg, teaching high school physics 2m6s.
Overview of Food Engineering
- The main topic of the talk is food engineering, a field that Dr. Chris Clark is passionate about, and which involves the application of scientific principles to the production of food, including the use of microstructural models to describe the structure of foods like ice cream and bread 4m42s.
- Dr. Chris Clark's work in food engineering has involved the use of various techniques, including computer tomography and fMRI machines, to study the structure and properties of foods, and to understand how they interact with the human senses 6m15s.
Sensory Perception and the Sense of Sour
- The talk will explore the science of sensory perception, including the five basic senses, which are sweet, sour, salty, umami, and bitter, and will focus specifically on the sense of sour, using a tangible and palpable experience involving sweets provided to the audience 8m40s.
- Dr. Chris Clark invites a group of volunteers, including some of his students, to participate in an experiment to explore the science of sour, and explains that the experience will be shared with the online audience through the volunteers' reactions 10m50s.
- The human tongue has a specific taste receptor designed to deal with sour tastes, which are triggered by acids that latch onto the receptor and trigger an electrical signal to the brain 10s.
The Science of Sour Tastes and Acids
- Not all acids are created equal, and from a food engineering perspective, it is interesting to explore the science of sour, particularly in confectionery or candies, where different acids can produce distinct sour sensations 1m30s.
- Citric acid is one of the most well-known food acids, commonly associated with lemons, and is used to create a sour taste in sweets, such as a little yellow gummy bear that becomes sticky when citric acid is added 2m6s.
- The sensation of sour has a profile that can be described using a graph of intensity versus time, with an initial sharp and high peak, followed by a dip, and then a gradual dissipation, which is referred to as the "zing" of sour 4m30s.
Exploring Different Types of Acids in Food
- Another type of acid, malic acid, is found in apples and produces a different kind of sour taste, which can be experienced by consuming a green gummy bear or a similar sweet that contains malic acid 6m0s.
- The experiment involves consuming the sour sweets and observing the reactions, with the understanding that the sensation of sour can vary depending on the type of acid used, such as citric acid or malic acid 7m40s.
- The profile of malic acid is strong, slightly more delayed, but it lingers before it decays, and is described as having a more aggressive consistency than citric acid, which is found in lemons 10s.
Combining Acid Profiles for Unique Flavors
- By mixing different acid profiles together, a new profile can be created, such as combining the sharpness of lemon with the aggressiveness of malic acid to create a unique sensation 2m6s.
- The mixture of malic and citric acid is often used to create a flavor called blue raspberry, which is commonly found in sour sweets, and the color blue is often associated with sour tastes 4m30s.
Taste Desensitization and Sensory Experience
- The human taste buds can become desensitized to acidity over time, which is why the sensation of eating sour sweets may not be as intense after repeated exposure 6m15s.
Introduction to Fizzy Sweets and Chemical Reactions
- Fizzy sweets are a type of candy that creates carbon dioxide gas in the mouth, producing a fizzy sensation, and can be made using ingredients such as baking soda and citric acid 10m0s.
- A chemical reaction between baking soda and citric acid can be triggered by the presence of moisture, such as saliva, to create a fizzy sensation in the mouth 12m30s.
Creating Fizzy Sweets: Sherbet and the Sherbet Fountain
- The combination of baking soda, citric acid, and sugar can be used to make a type of sweet called sherbet, which produces a foamy and cooling sensation in the mouth 14m45s.
- A sweet called a sherbet fountain is available in the UK, which is a tube of sherbet that you dip stuff in and then suck the sherbet off 10s.
Design and Attempt of the Sherbet Fountain Experiment
- A more literal version of the sherbet fountain is created by filling a bottle with about 20 g of sherbet and water, and then shaking it up vigorously, but the initial attempt at creating a fountain is unsuccessful 42s.
- A backup experiment is prepared using half a kilo of sherbet and 12 L of water, which is placed in a device made from a lady's tight, with a pipe going down through the middle, and the mixture is allowed to react and build up pressure 2m6s.
Execution and Success of the Sherbet Fountain
- The device is designed to release the built-up pressure and force the liquid down and up through the central tube, creating a fountain effect, and the experiment is triggered when the pressure reaches around 2 bar 4m30s.
- The sherbet fountain is successfully created, with the pressure building up to 1 and 1/2 bar before being released, and the resulting fountain is demonstrated to the audience 6m30s.
- The experiment requires patience, as the reaction needs time to happen, and the device is designed to withstand the pressure build-up, with the valve being released to create the fountain effect 5m40s.
