the sugars and flavorings in chewing gum, but not the gum base itself. this allows for gum to be chewed for a long time without breaking down in the mouth like conventional foods. chewing gum can be classified as a product containing a liquid phase and a crystalline phase, providing gum with its characteristic balance of plastic and elastic properties. stickiness while hydrophobic polymers beneficially repel water and contribute to chewiness, they also detrimentally attract oil. the stickiness of gum results from this hydrophobic nature, as gum can form bonds and stick when it makes contact with oily surfaces such as sidewalks, skin, hair, or the sole of one's shoe. to make matters worse, unsticking the gum is a challenge because the long polymers of the gum base stretch, rather than break. the sticky characteristic of gum may be problematic during processing if the gum sticks to any machinery or packaging materials during processing, impeding the flow of product. aside from ensuring that the machinery is free from lipid-based residues, this issue can be combatted by the conditioning and coating of gum toward the end of the process. by adding either a powder or a coating to the exterior of the gum product, the hydrophobic gum base binds to the added substance instead of various surfaces with which it may come in contact. bubble-blowing capability bubblegum bubble bubblegum bubbles are formed when the tension and elasticity of gum polymers acts against the constant and equally dispersed pressure of air being directed into the gum bolus. bubble gum bubbles are circular because pressure from the focused air being directed into the bolus acts equally on all of the interior surfaces of the gum cud, uniformly pushing outward on all surfaces as the polymers extend. as the bubble expands, the polymers of the gum base stretch and the surface of the bubble begins to thin. when the force of the air being blown into the bubble exceeds the force that the polymers can withstand, the polymers overextend and the bubble pops. due to the elastic attributes of chewing gum, the deflated bubble recoils and the wad of gum is ready to continue being chewed. gum bases with higher molecular weights are typically used in gums intended to meet bubble-forming expectations. higher molecular weight gum bases include longer polymers that are able to stretch further, and thus are able to form larger bubbles that retain their shape for a longer time. flavor release flavor delivery is extended throughout the mastication process by timed release of different flavor components due to the physical-chemical properties of many of chewing gum's ingredients. during the first three to four minutes of the chew, bulking agents such as sugar or sorbitol and maltitol have the highest solubility and, therefore, are chewed out first. as these components dissolve in the consumers' saliva and slide down the esophagus, they are no longer retained in the gum base or perceived by the chewer. during the next phase of the chew in the four to six-minute range, intense sweeteners and some acids are dissolved and chewed out. these components last slightly longer than the bulking agents because they have a slightly lower solubility. next, encapsulated flavors are released during either 10–15 minutes into the chew or after 30–45 minutes. encapsulated flavors remain incorporated in the gum base longer because the molecules that they are encapsulated in are more easily held within the gum matrix. finally, during the last phase of the chew, softeners such as corn syrup and glycerin and other textural modifiers are dissolved, resulting in a firming up of the gum and the end of the chew. studies have shown that gum flavor is perceived better in the presence of sweetener. companies have started to create chemical systems in gum so that the sweetener and flavor release together in a controlled manner during chewing. cooling sensation a cooling sensation is achieved through the chemical phenomenon of the negative enthalpy of dissolution that occurs with bulk sweeteners, such as the sugar alcohols. the enthalpy of dissolution refers to the overall amount of heat that is absorbed or released in the dissolving process. because the bulk sweeteners absorb heat as they dissolve and have a negative enthalpy, they yield a cooling sensation as they are dissolved in a consumer's saliva. health effects brain function a review about the cognitive advantages of chewing gum by onyper et al. (2011) found strong evidence of improvement for the following cognitive domains: working memory, episodic memory and speed of perception. however the improvements were only evident when chewing took place prior to cognitive testing. the precise mechanism by which gum chewing improves cognitive functioning is however not well understood. the researchers did also note that chewing-induced arousal could be masked by the distracting nature of chewing itself, which they named "dual-process theory", which in turn could explain some of the contradictory findings by previous studies. they also noticed the similarity between mild physical exercise such as pedaling a stationary bike and chewing gum. it has been demonstrated that mild physical exercise leads to little cognitive impairment during the physical task accompanied by enhanced cognitive functioning afterwards. furthermore, the researchers noted that no improvement could be found for verbal fluency, which is in accordance with previous studies. this finding suggests that the effect of chewing gum is domain specific. the cognitive improvements after a period of chewing gum have been demonstrated to last for 15–20 minutes and decline afterwards. dental health sugar-free gum sweetened with xylitol has been shown to reduce cavities and plaque. the sweetener sorbitol has the same benefit, but is only about one-third as effective as xylitol. other sugar substitutes, such as maltitol, aspartame and acesulfame k, have also been found to not cause tooth decay. xylitol is specific in its inhibition of streptococcus mutans, bacteria that are significant contributors to tooth decay. xylitol inhibits streptococcus mutans in the presence of other sugars, with the exception of fructose. xylitol is a safe sweetener that benefits teeth and saliva production because, unlike most sugars, it is not fermented to acid. daily doses of xylitol below 3.44 grams are ineffective and doses above 10.32 grams show no additional benefit. other active ingredients in chewing gum include fluoride, which strengthens tooth enamel, and p-chlorbenzyl-4-methylbenzylpiperazine, which prevents travel sickness. chewing gum also increases saliva production. food and sucrose have a demineralizing effect upon enamel that has been reduced by adding calcium lactate to food. calcium lactate added to toothpaste has reduced calculus formation. one study has shown that calcium lactate enhances enamel remineralization when added to xylitol-containing gum, but another study showed no additional remineralization benefit from calcium lactate or other calcium compounds in chewing-gum. other studies indicated that the caries preventive effect of chewing sugar-free gum is related to the chewing process itself rather than being an effect of gum sweeteners or additives, such as polyols and carbamide. a study investigating the in situ effect of casein phosphopeptide–amorphous calcium phosphate (cpp–acp) found that its incorporation into a sugar-free gum increases the remineralization / protection of eroded enamel surface significantly. gum chewing is regarded as a helpful way to cure halitosis (bad breath). chewing gum not only helps to add freshness to breath but can aid in removing food particles and bacteria associated with bad breath from teeth. it does this by stimulating saliva, which essentially washes out the mouth. chewing sugar-free gum for 20 minutes after a meal helps prevent tooth decay, according to the american dental association, because the act of chewing the sugar-free gum produces saliva to wash away bacteria, which protects teeth. chewing gum can also help with the lack of saliva or xerostomia since it naturally stimulates saliva production. saliva can also promote enamel remineralization as long as it does not become too acidic. masumoto et al. looked at the effects of chewing gum after meals following an orthodontic procedure, to see if chewing exercises caused subjects pain or discomfort, or helped maintain a large occlusal contact area. 35 adult volunteers chewed gum for 10 to 15 minutes before or after three meals each day for 4 weeks. 90% of those questioned said that the gum felt "quite hard", and half reported no discomfort. use in surgery several randomized controlled studies have investigated the use of chewing gum in reducing the duration of post-operative ileus following abdominal and specifically gastrointestinal surgery. a systematic review of these suggests gum chewing, as a form of "sham feeding", is a useful treatment therapy in open abdominal or pelvic surgery, although the benefit is less clear when laparoscopic surgical techniques are used. chewing gum after a colon surgery helps the patient recover sooner. if the patient chews gum for fifteen minutes for at least four times per day, it will reduce their recovery time by a day and a half. the average patient took 0.66 fewer days to pass gas and 1.10 fewer days to have a bowel movement. saliva flow and production is stimulated when gum is chewed. gum also gets digestive juices flowing and is considered "sham feeding". sham feeding is the role of the central nervous system in the regulation of gastric secretion. stomach chewing gum is used as a novel approach for the treatment of gastroesophageal reflux disease (gerd). one hypothesis is that chewing gum stimulates the production of more bicarbonate-containing saliva and increases the rate of swallowing. after the saliva is swallowed, it neutralizes acid in the esophagus. in effect, chewing gum exaggerates one of the normal processes that neutralize acid in the esophagus. however, chewing gum is sometimes considered to contribute to the development of stomach ulcers. it stimulates the stomach to secrete acid and the pancreas to produce digestive enzymes that aren't required. in some cases, when consuming large quantities of gum containing sorbitol, gas and/or diarrhea may occur. controversies classification as food controversy arises as to health concerns surrounding the questionable classification of gum as food, particularly in regard to some alternative uses for gum base ingredients. according to the u.s. food and drug administration (fda), chewing gum is considered a food, as the term "food" means "a raw, cooked, or processed edible substance, ice, beverage, or ingredient used or intended for use or for sale in whole or in part for human consumption, or chewing gum". chewing gum is defined as a food of minimal nutritional value. however, many of the ingredients in gum base have uses in inedible products, which raises concern in some consumers. polyethylene, one of the most popular components of gum base, belongs to a common group of plastics and is used in products from plastic bags to hula hoops. polyvinyl acetate is a sticky polymer found in white glue. butyl rubber is typically used in caulking and the lining of car tires, in addition to its role in gum base. paraffin wax is a byproduct of refined petroleum. possible carcinogens concern has arisen about the possible carcinogenicity of the vinyl acetate (acetic acid ethenyl ester) used by some manufacturers in their gum bases. currently, the ingredient can be hidden in the catch-all term "gum base". the canadian government at one point classified the ingredient as a "potentially high hazard substance." however, on 31 january 2010, the government of canada's final assessment concluded that exposure to vinyl acetate is not considered to be harmful to human health. this decision under the canadian environmental protection act (cepa) was based on new information received during the public comment period, as well as more recent information from the risk assessment conducted by the european union. choking and excretion of swallowed gum various myths hold that swallowed gum will remain in a human's stomach for up to seven years, as it is not digestible. according to several medical opinions, there seems to be little truth behind the tale. in most cases, swallowed gum will pass through the system as quickly as any other food. there have been cases where swallowing gum has resulted in complications in young children requiring medical attention. a 1998 paper describes a four-year-old boy being referred with a two-year history of constipation. the boy was found to have "always swallowed his gum after chewing five to seven pieces each day", being given the gum as a reward for good behavior, and the