Food Science Experiments to Support the Teaching of the Science and Technology Curriculums |
Secondary teaching resources developed by NZIFST
Experiments for High School Sciences Experiment 1: Catalase Activity  Description: Practically all biological reactions involve the use of specialised catalysts called enzymes. Enzymes are a type of protein and are naturally present in all living things (e.g. plant, animal, and microbial cells). Enzymes have been important in food processing since ancient times. They were first used in the production of foods and beverages such as wine and cheese. This experiment will show that enzymes naturally present in plant tissue can be inactivated by heating. The experiment uses potatoes as an example of a vegetable that contains high levels of the catalase enzyme, and will illustrate to the student that: 1. Enzymes are naturally present in plant tissue. 2. Enzymes can be controlled by altering their environment, e.g. heating 3. Enzymatic activity (catalase enzyme) can be determined by monitoring the enzyme’s ability to decompose hydrogen peroxide into oxygen and water. Components for download:
 Experiment 2: Peroxide Value (Titration)  Description: Lipids include fats, oils, waxes, other sterols, and most steroids. They are generally classified as organic substances that are soluble in organic solvents but only sparingly soluble in water. Food lipids are made up of mostlyfats (solid at room temperature) and oils (liquid at room temperature), plus 5%sterols (e.g. cholesterol). Lipid oxidation results in the production of off-flavours and odours, which is referred to as oxidative rancidity. Other effects of lipid oxidation include a decrease in nutritive value, colour changes, and sometimes the production of toxic compounds. The more oxidised the food lipids, the less desirable the food is to eat. A means of measuring the degree of oxidation of a fat or oil sample is to determine the peroxide value. This experiment will illustrate that: 1. You can determine if a fat or oil has become rancid by calculating its peroxide value using titration techniques. 2. Oxidation of fats and oils occurs rapidly when they are exposed to high temperatures. 3. Antioxidants can be used to reduce the rate of oxidation of fats and oils. Components for download:
Experiment 3: Extraction of Fats from Foods (Gravimetric Analysis)  Description: The fats (solid at room temperature) and oils (liquid at room temperature) found in our foods are usually present in the form of triglycerides. Triglycerides are formed when fatty acids combine with glycerol. The chemical make up of a fat or oil (i.e. the types of fatty acids that make up the triglycerides) determines whether the triglyceride is solid or liquid at room temperature. Fats and oils are organic substances that are soluble in organic solvents but only sparingly soluble in water. Solvent extraction can be used to extract lipids from foods. Once the food lipids have been extracted from the food, the solvent can be evaporated off leaving just the extracted lipids. This experiment will illustrate: 1. The use of solvent extraction to recover and and quantify the amount of fat in foods 2. Fat from different sources can be different in appearance. Components for download: N.B. Older versions of MS Word may not be able to accurately reproduce some graphs and images, so FlashPaper documents have been posted here as an alternative. FlashPaper documents can be printed but are not editable.
Experiment 4: Presence of Protein in Foods (Qualitative Analysis)  Description: Proteins are polymers of amino acids linked by peptide bonds. Each protein is made up of a unique sequence of amino acids of a particular chain length. Proteins in your body include: structural tissues (e.g. skin, tendons); the haemoglobin in your blood and myoglobin in your muscles, which help carry essential oxygen in your body; your muscles which give you the ability of movement; components that help to regulate body processes (e.g. enzymes, hormones); and components involved in your immune function (e.g. antibodies). Proteins in food will provide your body with the essential building blocks it needs to fulfil these functions as well as providing your body with energy. For this reason, it is essential that everyone eats protein-containing foods. However, the way some food products are processed will affect their final protein content.This experiment will illustrate: 1. That you can detect whether a food contains protein (e.g. egg white, cheese, butter, cornflour, marshmallow) using the biuret test. 2. Whether the foods contain short-chain polypeptides or proteins made up of three or more amino acids. Components for download: N.B. Older versions of MS Word may not be able to accurately reproduce some graphs and images, so FlashPaper documents have been posted here as an alternative. FlashPaper documents can be printed but are not editable.
Experiment 5: Monitoring changes in lactic acid concentration and pH during the production of Sour Cream  Description: A wide variety of foods such as yoghurt, sauerkraut, cheese, beer, wine, bread, soy sauce and coffee beans, owe their production and characteristic flavours and textures to the fermentative activities of micro-organisms. Micro-organisms involved in fermentation reactions include molds, yeasts (bread, beer and wine) and a group of bacteria collectively referred to as Lactic acid bacteria. Such micro-organisms use the sugars in food as a source of energy.Lactic acid causes the pH of the food to drop, which kills the pathogenic bacteria and inhibits the growth of many of the common spoilage micro-organisms. Other chemicals produced give the foods their distinctive flavour and odour.This experiment will illustrate: 1. The principals behind the production of sour cream 2. Gain experience in acid titrations and pH measurement. Components for download:
Experiment 6 (follows on from Experiment 5): Isolating bacteria from sour cream Description: A wide variety of foods such as yoghurt, sauerkraut, cheese, beer, wine, bread, soy sauce and coffee beans, owe their production and characteristic flavours and textures to the fermentative activities of micro-organisms. Micro-organisms involved in fermentation reactions include molds, yeasts (bread, beer and wine) and a group of bacteria collectively referred to as Lactic acid bacteria. Like all bacteria the lactic acid bacteria in sour cream are not visible to the unaided human eye. If given suitable conditions, however, bacteria will multiply and form colonies(clusters) of millions of cells, which are visible to the unaided human eye. Microbiologists frequently use this ability of the cells to grow up and form colonies to isolate bacteria from foods and to determine what types and how many bacteria are present. This experiment will illustrate: 1. How you can isolate bacteria from sour cream 2. A simple technique you can use to help view bacteria using a microscope Components for download:
Other experiments developed by NZIFST: Secondary school Food Technology workshop: The Role of Water in Food: Understanding Mouldy Bread and Soft Crackers |
