PREPARED BY: Dr. Bernard Cole. Pr. Sci. Nat.
1. INTRODUCTION TO GELATINE.
Gelatine is a wholesome food protein derived from mammalian skin and bone. It is unique in that a dilute solution in water forms a thermally reversible elastic gel, which melts at below body temperature, hence jellies made from gelatine have a melt in the mouth texture with excellent flavour release. Gelatine (spelled gelatin by some) has a large variety of useful properties besides forming a gel with water. Its adhesive properties are used in tableting and sticking together the layers of Liquorice All-sorts. Its crystallisation control properties are used in making ice-lollies and ice cream. Its film forming properties are used in making hard and soft capsules, which together with its foaming properties are used in the manufacture of marshmallow products and its emulsifying properties are utilised in making toffees and ice cream. Its thickening properties are used in powdered soup formulation and its water binding property is used in the manufacture of canned meats. Finally, at higher concentration it binds the ingredients of gelled confectionery into jelly-babies and a host of similar products. Besides these uses, gelatine is also being shown to have applications in combating osteoporosis and arthritis.
Gelatine is derived from the Latin verb gelare meaning Ato congeal@ and has been known for thousands of years. There is an ancient stone carving found in the ancient city of Thebes from the time of Thotines III (c.1000 BC) which showed the veneering of a rare red wood over yellow sycamore using glue derived from hide, by cooking. During Roman times Pliny wrote, AGlue is cooked from the hides of bulls.@ Then during the Elizabethan period, Shakespear made reference to glue in his writings and commercially glue was available in England from about 1700.When one makes soup and allows it to cool and the soup gels, it is the gelatine formed from heating collagenous materials that is responsible for the gel. However, the development of gelatine as an isolated food ingredient has only occurred over the last 150 years or so, and today the world production is about 220 000 tons per annum of which some 60 % is used in the food industry.
3. PRODUCTION AND PROCESSING.
Gelatine is produced from two main sources of raw material, namely skin and bone. The production from bone requires that the bone be crushed, degreased and all meat removed before
demineralisation using dilute hydrochloric acid to solubalize the calcium carbonate and phosphate in the bone. The residual protein matrix (collagen I) is then converted to gelatine by heating in water, filtration and ion-exchange of the resulting solution to remove contaminants, and then the solution is concentrated, gelled and dried. Finally the dry gelatine can be milled to a fineness most suited to its use i.e. fine ground for fast dissolving or coarse ground for minimal foam generation in confectionery manufacture.
In the manufacture of gelatine from skin, the process depends very much on the age of the animal. For young animal hide, the hide can be simply acidified to about pH 4 and then warmed to denature the collagen, which then dissolves as gelatine. Older bovine hide requires an alkaline pretreatment to separate hair and Acondition@ the hide to make it dissolve in hot water. After the alkaline treatment which has a marked chemical effect on the hide and causes dissolution of most of the non-collagen components, the hide is acidified and then dissolved in hot water as with young animal hide. The gelatine solution is then filtered, ion-exchanged, sterilized, concentrated, gelled and dried normally. It should be noted that the alkali process produces a gelatine with an isoelectric point (pI) of about 5 whereas gelatins produced without any alkaline treatment of the collagen have a pI of 7 to 9. For the housewife this has no importance but in more demanding applications pI can be very important.
Gelatine is usually used as a solution in water and the solution is best made in one of two ways.
For a dilute solution, a fine gelatine powder can be stirred into boiling water. As soon as the gelatine is dissolved the solution should be cooled by the addition of cold water.
For a more concentrated solutions, one part of gelatine should be stirred vigorously into two parts of water. This mixture should be allowed to stand for thirty minutes, during which time the gelatine will swell and the particles will soften. The resulting paste is then added to hot syrup in confectionery manufacture. In the kitchen, heating using a double boiler until it is clear and free from solids can dissolve the paste. Alternatively heating judiciously in a microwave oven can dissolve the paste until clear and free of undissolved solids.
It should always be remembered that heating, slowly destroys gelatin=s gelling ability so one should always use the least amount of heating possible and for the shortest time possible.
Generally speaking to make a refrigerated table jelly one needs 2 % gelatine in the water or 10 g to 500 ml water. Marshmallows requires about 2.5 % gelatine by weight and French jellies or jelly babies require 4 to 6 % gelatine by weight.
When used as a dietary supplement it is necessary to consume some 7 to 10 g pure gelatine daily. This would be equivalent to about 120 g jelly babies per day or 400 ml jelly which may not be practical, in which case, 2 heaped teaspoons of powder stirred into about 100 ml fruit juice and drunk as a slurry, can be an alternative means of consuming the required quantity.
The domestic uses of gelatine are many. A complete meal can be based on gelatine, from dips, through seafood, entrée, garnished/aspic cold main course or gelatine based relishes for hot main courses, moulded brawns or savoury pies and then flans, cheesecake or jelly deserts. Finally there can be nothing more decadent than to end the meal with toasted marshmallows.
Another tip is that instead of brushing bought pies with egg white before baking, a thin solution of gelatine will impart the same golden brown colour to the baked pie without leaving the rest of a broken egg to be used up somehow. Recipe books should be available from manufacturers like Gelita South Africa, PO Box 5019, West Krugersdorp. 1742.
Gelatine must never be used to set fresh pineapple or pawpaw fruit. The enzyme bromelain in pineapple and papain in pawpaw will prevent the setting of the gelatine. Cooked or canned pineapple pieces can be set in jelly quite successfully.
There are a large number of additional uses of gelatine. An example is the use in the manufacture of stirred yogurt to prevent synaeresis or Awheying off@. Gelatine is also used to stabilise thickened cream and low fat spreads and to clarify fruit juices including wine.
5. PRODUCTS AVAILABLE.
Many countries have their own gelatine manufacturer. Hence, wherever one happens to be there will probably be a brand specific to that area. In South Africa, Gelita SA are the local manufacturers and their product is available in most supermarkets as ADavis Gelatine@.
Nabisco also makes unflavoured gelatine available under their own brand name.
The product is available as 5 x 10 g sachets (1 sachet /500 ml water) or in packets of 125 g to 250 g.
In Germany, a local manufacturer makes gelatine available in a leaf form, each leaf being about 2 g of gelatine. This product, in 20 g packs, is supplied by some outlets catering for the AContinental@ market. Finally, a gelatine derived from fishskin is available from outlets specialising in the kosher market. From the gelling point of view all these gelatines are equivalent i.e. some 2 % is required to set water under refrigeration (5EC).
Some puddings in the market place contain Ainstant@ gelatine i.e. they can be made without preheating to dissolve the gelatine. These gelatines are dried from the liquid state by spray or drum drying and a clear product can not be made from them without heating, so this gelatine is only used to make blancmange or milky products and at present the pure gelatine is not made available to the public, mainly because of the processing difficulties.
Gelatine, when supplied by a reputable manufacturer is a perfectly safe and wholesome foodstuff. The South African product carries the SABS mark, which is an added guarantee of wholesomeness and safety. In addition, probably because gelatine is a commodity in international trade, the minimum specification for gelatine sold in South Africa is laid down in the regulations to the Foodstuffs, Cosmetics and Disinfectants Act 54 of 1972. From the medical point of view, there are almost no documented instances of allergy and jelly is used in hospital as a convalescent food because of its easy digestibility and nutritional value.
7. STORAGE & SHELF LIFE.
Dry gelatine in powder form has an indefinite shelf life if stored under clean, dry and well ventilated conditions. During the first year after manufacture it may loose up to 5 % of its gel strength and after that, loss of gel strength over the next 4 years can also be 5 % but thereafter loss of gel strength virtually ceases.
There is one exception that must be mentioned. If dry gelatine is stored in a fairly new kitchen cupboard the formaldehyde from the adhesives used in the cupboard can react with the gelatine rendering it insoluble in water. For this reason, and because gelatine is often stored for long periods, it is recommended that gelatine should be transferred into a well sealed glass container as soon as possible after purchase.
One must never loose sight of the fact that gelatine in solution is an excellent nutrient for bacteria, so diligent hygiene must be observed when preparing gelatine containing products and storage of these products under refrigeration can not be indefinite and preferably should not exceed 48 hours.
Gelatine solutions can not be deep frozen because this will cause synaeresis or separation of the solution into water and a gelatine containing concentrate.
Gelatine products, however, can be preserved for extended periods using benzoic acid and sorbic acid or low water activity conditions.
Gelatine packaging needs to be hygienic and prevent the free ingress of atmospheric moisture. Dry gelatine at 10 % to 12 % moisture content is in equilibrium with air at a relative humidity of about 60 %. Of importance is the fact that at this moisture content and at 20EC to 30EC gelatine is well below its glass transition temperature Tg, and so it can be expected to be very stable and resistant to bacterial attack. Consequently, it is the practice to package gelatine in plastic lined paper containers of adequate mechanical strength to handle the mass involved and preferably they should be hermetically sealed to prevent contamination of the contents.
9. RELIGIOUS CONSIDERATIONS.
Because gelatine is a protein derived from animal sources, there are problems from religious points of view and the strict vegetarian can not use it. From the Kosher and Halaal points of view there should be no problem with gelatine because both religions have provision for an inedible substance (skin) to be transformed into an acceptable edible product (gelatine). However in the case of gelatine the problem is confounded because there is provision for the animals used to be killed in accord with Muslim or Jewish law and hence there are some who contend that gelatine additionally needs to be produced from suitably slaughtered animals. The solution to the problem has been to use gelatine from fish skin because in Jewish law the whole of a scale bearing fish is edible and kosher. The problem with this is that cold sea-water fishskin gelatine has a very poor gel strength and the availability of warm fresh-water fish skin from which a high gel strength gelatine can be produced, is very limited.
10. HEALTH AND NUTRITIONAL HIGHLIGHTS.
Gelatine composition (Typical):
per 100 g
Gelatine usually forms a small part of any foodstuff (2 to 6 %) and hence its nutritional value is seldom considered important. As a protein, it is deficient in tryptophan, which is one of the nine essential amino acids. As a result, gelatine has no Biological Value! However, gelatine is seldom consumed in isolation or as a sole source of protein in the diet, so in a mixed diet gelatine has the advantage of meat products, of being high in the essential amino acid lysine. Thus, it can be considered a valuable compliment to any largely vegetable diet. Also, it has been shown to enhance the protein nutritional value of bread.
From the point of view of the dietary benefits of gelatine, it has long been said to have beneficial effects for those suffering from nail defects. The benefits of gelatine consumption on nail growth and nail strength were documented in double-blind studies conducted on nurses in the 1950s.
More recently it has been found that the degree of the progress of osteoporosis can be measured by the excretion of collagen terminal amino acids in the urine. It follows that osteoporosis is associated with the destruction of bone collagen and it has been shown that the ingestion of gelatine (derived from collagen) reduces the amount of degradation of the natural collagen and therefore reduces the amount damage done by this disease. Presumably, the enzymes that were degrading bone collagen are spent on degrading gelatine when it is available in sufficient quantity. Then again it has been known from double-blind studies that taking gelatine can alleviate the pain and inflamation caused by arthritis. A recent rodent study, using isotopically labeled gelatin, showed that most of the gelatine was found concentrated in the joints, which at last gave some indication of the mode of action of gelatine in arthritis i.e. it looks as though it is used in the cartilage repair processes! Other clinical statistical studies have indicated that gelatine promotes hair growth and it is well known that gelatine is substantive to hair and has many beneficial effects in that it has an antistatic effect, hair strengthening effect and improves hair gloss and repairs the damage caused by permanent-waving when incorporated at the level of about 0.5 % in shampoos and conditioners.
11. MEDICAL CONDITION ALERT.
Allergic reaction to gelatine is almost unknown and when observed the allergic reactions is invariably mild.
12. BRANDS AVAILABLE.
Davis Gelatine and Royal unflavoured gelatine in powder form.
Aquagel - from fishskin for kosher compliance.
Gelitagel - leaf gelatine from Germany.
Dr Oetker - is found occasionally.
13. FURTHER STUDY RESOURCES.
The Science and Technology of Gelatin. Ed. AG Ward & A
Academic Press. London, New York, San Francisco. 1977.
The Macromolecular Chemistry of gelatin. A. Veis. Academic Press, New York & London. 1964.
Gum Technology in the Food Industry. M. Glicksman. Academic Press. New York & London. 1969.
Gelatin Manufacturers Europe: http://www.gelatine.org/
Dr CGB Cole. Gelatine including Research: http://www.gelatin.co.za
Bender DA & Bender AE. Benders= dictionary of nutrition and food technology. 7th Ed. Woodhead Publishing Ltd. Cambridge England. 1999.
Glicksman. M. Gum Technology in the Food Industry. Academic Press. New York & London. 1969.
Osser S., Adam M., et al. Oral administration of 14C labled gelatin hydrolysate leads to an accumulation of radioactivity in cartilage of mice (C57/BL). Journal of Nutrition [JONUAI]. 129(10), 1892-1895. 1999.