Citric acid

UNDERSTANDING YOUR FOOD<br /> the ultimate educational resource<br /> TEACHER NOTES<br /> <br /> teachers’ notes A5.1<br /> A5. Citric acid<br /> This is a text based activity concerning citric acid.<br /> Answers for questions on Pupil activity sheet A5:<br /> 1. To calculate the angles required to produce a pie chart for soft<br /> drinks 48/100 x 360 = 172.8o<br /> for health salts 8/100 x 360 = 28.8oand so on.<br /> 2. A table seems the most appropriate form of presentation; its content<br /> will vary depending on the labels.<br /> 3.<br /> KS3/4<br /> science and food technology;<br /> possibly a homework written<br /> exercise<br /> Timing - 20 - 30 minutes<br /> Two pupil activity sheets A5<br /> accompany this activity.<br /> Type of food productFunction in this product<br /> beverages and soft drinkstaste; buffering properties; increase effectivenessof<br /> preservatives<br /> jams and jellies sour taste; acidic pH needed to make products set<br /> frozen food chelating agent; prevents colour and flavour<br /> deterioration<br /> fats and oils prevent oxidation<br /> processed cheeses emulsifying salt<br /> whipping cream stabiliser<br /> vegetable based dairystabiliser<br /> substitutes<br /> seafood increase effectiveness of preservatives and antioxidants<br /> cured meat productsincrease effectiveness of preservatives and<br /> antioxidants; modifies texture<br /> chelatingagent - removes trace<br /> metals which enhances the<br /> performance of antioxidants<br /> substances are given pH values<br /> between 1<br /> -14; acids have values7; pH 7 indicates<br /> neutrality.<br /> 4. a.pH- measurement of acidity or alkalinity of a system.<br /> b.Buffer- substances which are capable of reducing excess<br /> acidity/alkalinity so that the final pH remains the same.<br /> c.Emulsions- formed when tiny drops of one liquid are spread evenly<br /> through a second liquid; there are many examples of foods which are<br /> emulsions, such as ice cream, margarine and mayonnaise.<br /> 5. Foods containingpreservatives; some examples:<br /> pizza (pepperoni with cured pork and beef sausage), sodium nitrite E250<br /> mayonnaise, potassium sorbate E202<br /> chocolate Swiss roll, potassium sorbate E202<br /> Belgian buns, sodium propionate E281, sodium benzoate E211<br /> naan bread, calcium propionate E282<br /> 6. Foods containingantioxidants; some examples:<br /> cheese and ham pasties (the ham),sodium ascorbate E301<br /> pizza(as above), sodium ascorbate E301<br /> vinaigrette, butylated hydroxyanisole (BHA) E320<br /> <br /> CITRIC ACID pupil activity A5<br /> Many of the foods we eat areacidic, that is they contain acids. This explains their<br /> sharp taste. Natural foods like oranges, lemons, apples, tomatoes, cheese and<br /> yoghurt are all strongly acidic. Citrus fruits contain citric acid, apples and pears<br /> contain malic acid, cheese and yoghurt are rich in lactic acid.<br /> Citric acid was first extracted from lemon juice about 200 years ago. It is the most<br /> versatile and widely usedacidulant. It is found abundantly in nature. It is used<br /> extensively in foods, beverages and the pharmaceutical industry.<br /> Tasks<br /> Citric acid is economically very important. It is manufactured in 20 countrieswith<br /> world wide production, in 1997, in the region of 750 000 tonnes. Just over 35%of<br /> citric acid is manufactured in Europe, where about 250 000 tonnes of citric acidis<br /> used each year.<br /> The table below shows the % use of citric acid in the UK.<br /> PRODUCT % USE<br /> soft drinks 48<br /> health salts 8<br /> other foods 12<br /> confectionery 9<br /> detergents 16<br /> other uses 7<br /> 1.Construct apie chartto illustrate these figures.<br /> 2.Collect food labels and non-food product labels, like some medicines,<br /> where citric acid, E330, or its salts, E331, E332, E333, are present.<br /> Display your findings in a suitable way.<br /> Answer the following questions after you have read the information about<br /> citric acid (on next page).<br /> 3.Make a table which summarises the functions of citric acid and its salts in<br /> food. The first column should show the type of food product. The second<br /> should show the function of citric acid.<br /> 4. What is meant by:<br /> a.pH?<br /> b. abuffer?<br /> c.anemulsion?<br /> 5.From food labels, find the names of two food products which contain a<br /> preservative. Write down the name of the food, the name of the preservative<br /> and the E-number.<br /> 6.From food labels, find the names of two food products which contain an<br /> antioxidant. Write down the name of the food, the name of the preservative<br /> and the E-number.<br /> <br /> pupil activity A5 CITRIC ACID<br /> "Citric acid is used extensively in food and industrial applications because it has<br /> many important chemical properties.<br /> Citric acid (E330), sodium citrate (E331) and potassium citrate (E332) are widely<br /> used in beverages and soft drinks. A combination of these three substances is<br /> used to give flavour, provide buffering properties and increase the effectiveness of<br /> preservatives.<br /> In jams, jellies and preserves, citric acid is used to give a sour taste. An acidic pH<br /> (<7) is also needed for these products to set properly, i.e. to produce a gel.<br /> Citric acid is able to combine with free metals in foods that are frozen. This is<br /> described as being achelatingagent. This is important since it enhances the<br /> actions of antioxidants. Citric acid also prevents colour and flavour deterioration in<br /> frozen food.<br /> The oxidation of fats and oils in food products can be prevented by the addition of<br /> citric acid. It acts, again, by removing trace metals.<br /> Sodium citrate acts as an emulsifying salt in processed cheeses. It modifies the<br /> protein in the cheese enabling it to form an emulsion between the water and fat.<br /> This prevents the separation of these components and improves the body and<br /> texture of the cheese. Sodium citrate is also an important stabiliser in whipping<br /> cream and vegetable based dairy substitutes.<br /> Citric acid is used in seafood and cured meat products to increase the<br /> effectiveness of colours, flavourings, preservatives and antioxidants. It also modifies<br /> the texture of meat products.<br /> Citric acid and citrate salts have a number of medical uses. They are used as<br /> buffers in a wide range of pharmaceutical products. Effervescent formulations<br /> (such as Alka Seltzer) contain a mixture of citric acid and sodium bicarbonate to<br /> assist dissolving and to improve taste. Sodium citrate is added to human blood to<br /> prevent coagulation before it is used in transfusions, etc.<br /> Citric acid has many industrial uses, such as a laundry detergent, and a number of<br /> agricultural uses. Other uses include the production of concrete and mortar, a<br /> blowing agent in plastic production and an important component of many<br /> cosmetics and toiletries.<br /> It is a truly versatile compound!”