Making Chewing Gum

Of all the confectionary products, chewing gum rivals chocolate and candies as one of the most consumed products in the world. Chewing gum is a food which is primarily made from gum whether they are natural or man-made, various polymers and copolymers. It also includes other ingredients and food additives.

Chewing gum is good for you. There is gathering evidence in the medical field that chewing gum helps reduce stress, can help with a weight management programme and even reduce mental anxiety. It has certainly help revolutionise smoking cessation which also gave gum a new lease of life in product development and a rich vein for intellectual property.

History 

Chewing gum has an ancient history. It is a very odd habit when you think about it but it is something that we humans have been doing for millenia. The Ancient Greeks chewed tree sap resins from mastic trees but this practice died away. They did however give us the Greek word mastichan which means ‘to chew’ derived from the chewy sap called mastiche.

It seems the Ancient Americans were also chewing tree sap and this may have been happening 3000 years before Christ was born.  Chewing gum in the Americas continued throughout the centuries.

The spruce sap based resins and gums finally made way for petroleum based paraffin wax. To improve the palatability, sweetners including sugar were then added. Chewiness which is such a key consideration of gum could not be sustained with the oil based ingredients so a return to tree sap was made. So it was that the Mayan favourite of chicle or tsitle returned to the product development fold.

Commercial chewing gum was developed by John B. Curtis in 1848. back then it was known as State of Maine Spruce gum. Strangely he made a pink type because it was the only colour he had available..

The first patent for a chewing gum was granted in 1869. This was developed by of all people, a dentist known as William Semple who lived in Mount Vernon, Ohio. Then we see one of the great names in gum appear. William Wrigley Jr. started advertising commercial chewing gum in the 1920’s. His two product flavours were spearmint and Juicy Fruit which have continued to be major flavour brands ever since.

In 1928, Walter Diemer made the very first bubble gum which is a gum that allows you to blow bubbles although that could be disputed because bubble gum was known about in 1906.

The modern equivalents are now made with heavily regulated food ingredients but it comes down to one or to functional ingredients to produce a decent chewing gum. The first is chiclet or chicle gum which is a latex extracted from the Sapodilla tree. This latex is extremely sticky but ideal for producing some of the best gums in the world.

Basic Ingredients

Chewing gum is composed of a water insoluble gum base to which is added a variety of ingredients for taste including sweeteners, flavours and some other functional ingredients. As mastication continues, the water soluble part of the gum releases  flavour into the mouth whilst the sticky gum base remains in the mouth. For many manufacturers, it is their goal to maintain a persistent flavour release  as the gum is chewed and a great deal of effort has been spent trying to achieve this but with limited success.

The gum itself is often prepared as a thin plank like strip or a tablet. In many instances it is also coated with a hard shell to keep it water resistant and provide some crunch as a texture difference before the serious chewing begins..

Key ingredients added to gum are sweeteners, many of which are artificial. Typical sweetening agents include sugar, corn syrup and beet juice. The non-calorific sweeteners include the bulk polyol types such as sorbitol, xylitol and mannitol. Others include stevia and acesulfame K, aspartame and sweetener blends made of these ingredients. The sweetening agents are often added to the coating rather than the main center of the gum. When artificial sweeteners are used, these are added to between 0.10 and 0.15%w/w of the coating.

Flavours are added to give a specific taste and sensory appeal to the gum. These provide a long lasting, high intensity flavour and are always added at the end of manufacture. The most popular flavours are peppermint (or mint as it is often called), menthol and then various fruit flavours. Flavours are added in solid, liquid and microencapsulated formats. The liquid flavours can be water-soluble, oil-soluble and both oil and water-dispersible emulsions. Oil-soluble flavours are often used because they linger for longer in the gum base. The gum base is usually hydrophobic which means oil-soluble compounds are often retained within the matrix by loose associations.

Dispersing agents are added to syrup coatings to help with whitening and tack reduction. Typical anti-sticking agents include talc and titanium dioxide. The latter ingredient is usually preferred and is often added to the coating in a range of 0.3 to 0.6 %w/w.

The Insoluble Gum Or Gum Base

The gum base is the one ingredient that distinguishes chewing gum from any other foodstuff. It is always insoluble and has no nutritional value whatsoever. It is also one of the most commercially sensitive and lucrative aspects of gum manufacture. Interestingly, gum is exempt from labeling requirements according to the FDA so it remains commercially secret and is simply described as gum base.

Most people will be familiar with chicle gum latex as the basic natural substance for manufacture. However, most commercial production relies on a variety of ingredients to create the perfect mouthfeel. These include some if not all of the following:-

elastomers, resins, fats and oils, softeners, stabilizers, emulsifiers, thickeners, surface active agents, and inorganic fillers. All gum base must conform in the USA with the FDA 21 CFR 172.615 and the Food Chemicals Codex Specifications.

An elastomer is the technical term for the chewable latex. It includes not only chicle but natural rubber as well, crown gum, nispero chicle, rosidinha, jelutong, pendare, perillo, gutta hang kang, lechi-capsi, niger gutta, massaranduba balata, massaranduba chocolate, tunu are all natural latex gums.

We also have synthetic elastomers such as including polyisobutylene, isobutyleneisoprene copolymers, styrenebutadiene copolymers, polyvinyl acetate (PVA), polyisoprene, polyethylene, vinyl acetate – vinyl laurate copolymers, and combinations of some but generally not all of these. PVA is often used as it is odourless, colourless and tasteless. It is an alcohol-soluble thermoplastic with a specific gravity of 1.189.

A general purpose material for chewing gum is ester gum which is the glycerol ester of rosin (CAS No., 8050-31-5). Rosin is famous for being the sticky stuff used to make violin bows produce a sound when drawn across a metal string. Eastman produce a classic gum called Ester Gum 8D Resin which is also used for coatings. The manufacturers claim it has broad compatability with other elastomers like natural and synthetic rubber, ethylcellulose, polystyrene, many other natural resins, waxes and vinyl resins. A reasonably good solubility, a low acid number (which is 6 mg KOH/g, neutral odour and taste, a medium softening point and a thermoplastic resin.

A number of ingredient suppliers sell bubble and chewing gum bases.  Cafosa, which is a subsidiary of Mars have over 200 different kinds of gum bases available for commercial use.

Additional Functional Ingredients

As with toothpaste production, a tooth whitening agent can be added to the mix. Weak peroxide compounds are often used such as sodium or potassium percarbonate  (sodium carbonate peroxyhydrate). The percarbonate needs to be highly water soluble and must dissolve in the mouth to produce small, SAFE amounts of hydrogen peroxide which decolourise pigments on the teeth. Along with sodium bicarbonate, the percarbonate behaves to increase the alkalinity in the mouth.

Lecithin is needed in all cases especially when making the gum base to ensure there is an emulsifier present when water is added to the mix. It helps keep the chewing gum pleasant to chew especially after a long time of mastication. The final chewing gum should contain about 0.4 to 0.7 per cent lecithin because it helps other ingredients to dissolve as well such as flavourings. Lecithin reduces stickiness and contributes better elasticity to the chewing gum

Antioxidants are allowed in gum bases to prevent damage by free radicals during processing and during shelf-life. The most commonly used is butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and tocopherols.

Making A Gum Base

Production of a gum base is achieved using much more vigorous conditions than is needed for making the actual chewing gum. A typical recipe for various gum bases is:-

Base: Ester gum (88 per cent), rubber latex solids (10 per cent), lecithin (2 per cent).

Base: Chicle (30 per cent), jelutong (60 per cent), gutta soh (8 per cent), lecithin (2 per cent).

Base: Partially oxidised chicle (98 per cent), lecithin (2 per cent).

Base: Jelutong (dry) (80 per cent), gutta siak (18 per cent), lecithin (2 per cent).

As you can see in the preceding recipes, a variety of bases can be produced depending on the type of texture required for the gum.

Recipes For Chewing Gum

A typical formulation for a standard chewing gum which was devised by Atlas Food Laboratories and reported in Lees (2012) is:-

	Parts by weight
Gum base	16
Icing sugar	40
dextrose	10
Glucose syrup 42 DE	24
Sorbitol syrup (70% concentration)	4
Calcium carbonate	1
Maize starch	2
Glycerine	1
Hydrogenated palm kernel oil	1
Soyabean lecithin	0.5
Flavouring	0.5
Colouring	0.5

A typical formulation for a sugarless chewing gum which was also devised by Atlas Food Laboratories (Lees, 2012) is:-

	Suggested usage, (%)	Range (%)
Gum Base	25.0	25-26
Sorbitol (70% solution)	17.0	16-17
Crystalline sorbitol	36.0	36-40
Mannitol	18.6	14.5-17.1
Glycerine	0.5	0.5
Artificial Sweetener	0.5 to 1.5	0.5-1.5
Flavour	1.5	1.5

Changes in the level of any of these ingredients will significantly alter both texture and flavour of the gum. 

Part 1 – Dissolving the Gum Base

A gum base is prepared by dissolving the latex as small pieces or plugs into a stainless steel mixing vessel with a water or water/steam jacket for temperature regulation. The jacketed vessel needs baffles, especially a couple of Z-arms or sigma arms to help mix and fold the resulting gum mixture. Horizontal ribbon blenders are ideal for mixing. The gum base is usually heated in this chamber using steam for a few minutes to 60°C.

The gum pieces should melt when the temperature reaches 50 °C as the water temperature rises. At this point a paste is being produced to which more ingredients will be added. The relatively gentle temperature is possible with monitoring coupled to steam regulation.

Part 2 – Addition Of Ingredients

Whilst the gum base is melting, about 5 to 10 minutes later, portions of other ingredients especially sweeteners, are added. If sorbitol or maltitol is the sweetener, about a third of the total amount of each ingredient is added and allowed to dissolve into the liquid gum base before proceeding with the next addition. Mixing continues for between 2 and 5 minutes until it is noticed that all the addition has dissolved. The next portion is added and the process of mixing and dissolving is continued until all the sweetener ingredient is added.  

The remaining ingredients are added and can include the flavour, starch any alkali, various oils etc. The mixture should be continually blended until it looks homogeneous. This should take about 6 to 8 minutes.

The flavour is always the last ingredient to be added. This ingredient should be added in stages to ensure each portion is dissolved thoroughly into the gum mixture.

Blending of all the ingredients continues until the paste is homogeneous which means no streaks, lumps or other non-conformities are observed. It should have a dry surface rather than a gloss appearance. The gum temperature at this stage will be about 45 to 50°C (113 to 122°F). The gum continues to be kneaded until it is removed. If the temperature drops the gum mix stiffens and becomes difficult to roll and size.

Part 3 – Slab Or Tablet  Production

The final gum paste is removed from the kneading machine where it is formed into sticks or tablets. To begin, the mixture is usually poured onto cooling belts where they cooled with cold air. A number of operations then create the final product – extrusion, rolling and cutting, mechanical shaping amongst other processes are used. The final chewing gum is allowed to settle for between 24 to 48 hours.

A chewing gum might be coated by first wrapping it in an undercoat to help with adhesion before binding on further layers like liquid sugar. Some pellets are coloured and coated with a glazing agent such as a wax. A hard coating is often applied to protect the gum centre and provide a crunchy texture. The coating is often made of polyols. These are sometimes applied as a water absorbent powder which helps extend shelf-life further.

If chewing gum is to be dusted as you would a slab of pastry dough, then mannitol is the powder of choice. The non-coated types are covered in a sweet marble dust which stops the wrapper sticking to the product.

Bubble gums are usually prepared from gum bases containing soft polymers such as jelutong. Resins and plasticiers help to soften the gum base so that it can be masticated easily or blown.

Shelf-Life

One average two years or even longer if part of military rations which can be at least three years.

Problems And Issues In Gum Manufacture

Sweating occurs when the gum begins to breakdown or change its structure. The phenomenon is attributed to the following:-

• poor or inadequate conditioning of the gum as it is being produced
• processing with uneven moisture content throughout the blend
• use of too high a level of glucose or invert sugar syrup
• poor or unsatisfactory packaging
• poor storage especially in very high temperature conditions

Some gums feel gritty when sugars such as added icing sugar have too large a particle size. It can also reflect an incorrect balance between glucose syrup and sucrose. Shrinking is also highly problematic. This occurs when the gum is not conditioned properly during manufacture or when mixing and kneading are insufficient.

Chewiness

Chewing gums must have a certain degree of chewiness. This is a physical texture property. The gums are hydrophobic which helps with mastication. These gums repel water in the saliva which means they remain undissolved meanwhile the flavours and sweeteners are crushed and manipulated out of the base gum to provide prolonged taste. The gum can literally be chewed indefinitely. In structural terms, gum is a product containing a liquid phase and crystalline phase. the gum has a an interesting balance of both elastic and plastic properties which provides the characteristic chewing properties. 

Nutritional Benefits

Evidence has been gathered to suggest that chewing gum is very healthy for you. Chewing may reduce situational stress, manage weight, increase mental performance, and improve oral health.

Product Development Opportunities 

CA number of nutritionally beneficial ingredients have been added including vitamin C, niacin, vitamins B6 and B12. Caffeinated gum has been available since the turn of the century. It is available as an alternative source of caffeine to coffee, soda and energy drinks. Caffeine is more rapidly absorbed through the buccal cavity than in the gut so it has made a great deal of sense for chewing gum makers to add this ingredient. Some go as far as claiming caffeine is delivered quicker into the body than through an energy drink. Gum is also easier to store than a bottled beverage ! 

VE2 (Chicago, Ill. USA) produced an Energy Gum in 2008 that contained caffeine, niacin, vitamins B6 & vitamin B12, ginseng, and guarana. Two pieces of gum contain the same amount of caffeine as one 8-oz. energy drink or one cup of coffee.  

Mars Wrigley Confectionary launched  ‘Alert Caffeine Gum in mint and fruit flavours in Autumn 2017. The gum contains 40mg of caffeine per serving which is equivalent to the amount in half a cup of coffee. The offering comes after research shows that people who chew gum remain awake longer and this is boosted by the addition of caffeine. The confectionary is only for adults and not for children, pregnant or nursing women and anyone sensitive to caffeine. This gum comes in eight sticks.

Nicotine containing gum has also become a mainstream product as a way of helping to wean smokers off cigarettes. A significant meta-analysis of fourteen studies reveals that use of nicotine gum helps smokers reduce their level of smoking. Interestingly the same paper states ‘the use of gum in general medical practices is questionable’ (Lam et al., 1987). The level of research into these products is now extensive and has rejuvenated the chewing gum market.

Maintaining sweetness and flavour in a chewing gum has been a major concern for innovators. A number of patents are known:-

Cherukuri et al., (1990, 1992), De Roos (1990), Reed & Hook (1992).  

References

Cherukuri, S.R., Faust, S.M., and Mansukhani, G. (1992) Chewing gums having longer lasting sweetness. U.S. Patent 5,110,608

Fritz, D. (2006) Formulation And Production Of Chewing and Bubble Gum. Kennedy’s Books Ltd 303 pages

Lam, W., Sacks, H.S., Sze, P.C., Chalmers, T.C. (1987) Meta-Analysis Of Randomised Controlled trials Of Nicotine Chewing-Gum. the Lancet 330 (8549) pp. 27-30 https://doi.org/10.1016/S0140-6736(87)93061-3

Lees, R. (2012) Sugar Confectionary and Chocolate Manufacture. Springer Sci. & Business Media. 380 pages