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Why people prefer certain foods over others depends largely on a combination of taste and texture. While taste sensations are fairly well understood, scientists are just beginning to unravel the mystery of food texture.
Now, researchers at the Monell Chemical Senses Center in Philadelphia have found that an enzyme in saliva called amylase, which breaks down starch into liquid, could play a key role in determining the appeal of various textures of food. A new genetic study shows that people produce strikingly different amounts of amylase, and that the more of the enzyme people have in their mouth the faster they can liquefy starchy foods.
Scientists think this finding could help explain why people experience foods as creamy or slimy, sticky or watery, and that this perception could affect our preference for foods. For the numerous foods that contain starch, including pudding, sauces and even maple syrup, what can feel just right to some people is experienced as too runny or not melting enough for others because they produce different amounts of the enzyme.
The ability to quickly break down starch, which is a type of carbohydrate, is only one part of the puzzle that determines what people like to eat. Taste preferences are driven by a complicated interaction between taste buds and other receptors in the mouth and nose, and the messages they send to the brain. Culture plays a role, as people tend to like foods that are familiar, says Rick Mattes, a foods and nutrition professor at Purdue University in West Lafayette, Ind. And repetition sometimes can win out: Many people initially don't like oysters because of their slimy texture, for instance, but can come to enjoy them after several tries.
'We all have had the experience of liking a food that someone else complains is too tacky, or slippery, or gritty, or pulpy,' says Paul Breslin, a researcher at the Monell center and a professor at Rutgers University in New Brunswick, N.J. 'This is why a given line of product often comes in different textural forms,' such as orange juice with and without pulp, he says.
Starch comprises or is added to about 60% of the foods people typically eat, so determining how it is digested is key to understanding food-texture preferences, Monell center scientists say. Other research has shown that people have a preference for creamy sensations as well as for foods that start off solid and melt in the mouth such as ice cream and chocolate, says Dr. Breslin, who began the current research because of his interest in creaminess. Amylase also could help explain individual preferences for different brands of ice cream or yogurt, for instance, because they contain different amounts of added starch.
In their recent work, Monell researchers had 73 adults swirl around in their mouths solutions made up of different concentrations of starch -- blobs of translucent gelatinous substances with no particular taste -- and rate their runniness over the course of 60 seconds. Depending on the amount of amylase individuals produced, the starch could be reduced to liquid within seconds.
The researchers also took DNA samples of the participants from a blood sample or cheek swab and studied the link between the numbers of copies of a gene that turns on the production of amylase and how quickly the participant reported the sample turned runny. The findings showed that the number of copies of the gene, called AMY1, varied widely between individuals. People with higher numbers of gene copies reported that the starch turned to liquid more quickly. The study was published last month in PLoS ONE, a journal of the Public Library of Science.
The Monell researchers are now investigating whether people with more AMY1 copies see larger spikes in blood glucose after eating. They also plan to study the link between greater amylase production and food preferences, hypothesizing that people who make more of the enzyme will prefer starchy products because they get a faster blast of glucose into their bloodstream.
The role of amylase and the rate of starch breakdown also has implications for diabetes. People who digest starch quickly could be more likely to have larger spikes in blood-sugar levels and thus a need for the body to generate more insulin. This continued demand on the body might lead these people to become insulin resistant or even diabetic if the body's ability to produce insulin breaks down, says Abigail Mandel, Dr. Breslin's colleague at Monell and first author on the study.
Amylase and other enzymes in saliva could also help explain food-texture preferences that are known to vary with age, Dr. Breslin says. For instance, many young children dislike certain fruits because of a perceived sliminess -- think of the inside of a tomato. But people's saliva-flow rate tends to slow with age, which might affect their ability to break down starch in the mouth and reduce sensations of sliminess.
參考譯文：
renmenzhisuoyipianaimouxieshiwu，zhuyaoshiyinweishiwudeweidaohekougan。kexuejiamenduiweijiaodeyuanliyijingyoulexiangdangdelejie，danqueganggangkaishizheshoupojieshiwukougandemiti。
如今，美國費城蒙內爾化學感覺中心（Monell Chemical Senses Center）的研究人員已經發現，唾液當中有一種名為澱粉酶（Amylase）dewuzhi，zhezhongmeikeyirongjiedianfen，kenengzaiwomenpingjiashiwukouganyouliedeguochengzhongfahuizheguanjiandezuoyong。yixiangxindeyichuanxueyanjiubiaoming，rentizhizaodianfenmeideshuliangyinreneryi，huxiangzhijiandechayidadejingren。kouqianglidedianfenmeiyueduo，rongjiedianfenshiwudesuduyejiuyuekuai。
科學家們認為，這一發現有助於解釋，人們為何會對食物產生或滑膩或濃稠、或(huo)粘(zhan)牙(ya)或(huo)鬆(song)軟(ruan)的(de)口(kou)感(gan)，與(yu)此(ci)同(tong)時(shi)，不(bu)同(tong)的(de)口(kou)感(gan)又(you)會(hui)影(ying)響(xiang)我(wo)們(men)對(dui)食(shi)物(wu)的(de)偏(pian)好(hao)。含(han)澱(dian)粉(fen)的(de)食(shi)物(wu)為(wei)數(shu)眾(zhong)多(duo)，其(qi)中(zhong)包(bao)括(kuo)布(bu)丁(ding)和(he)醬(jiang)料(liao)，甚(shen)至(zhi)還(hai)包(bao)括(kuo)楓(feng)糖(tang)。吃(chi)到(dao)這(zhe)類(lei)食(shi)物(wu)的(de)時(shi)候(hou)，有(you)些(xie)人(ren)可(ke)能(neng)覺(jiao)得(de)口(kou)感(gan)剛(gang)剛(gang)好(hao)，另(ling)一(yi)些(xie)人(ren)的(de)感(gan)覺(jiao)則(ze)是(shi)太(tai)過(guo)鬆(song)軟(ruan)，還(hai)有(you)些(xie)人(ren)的(de)感(gan)覺(jiao)又(you)是(shi)不(bu)夠(gou)化(hua)渣(zha)。之(zhi)所(suo)以(yi)會(hui)有(you)這(zhe)樣(yang)的(de)差(cha)異(yi)，原(yuan)因(yin)就(jiu)是(shi)人(ren)體(ti)製(zhi)造(zao)澱(dian)粉(fen)酶(mei)的(de)數(shu)量(liang)各(ge)不(bu)相(xiang)同(tong)。
澱dian粉fen是shi一yi種zhong碳tan水shui化hua合he物wu，快kuai速su分fen解jie澱dian粉fen的de能neng力li隻zhi是shi決jue定ding人ren們men食shi物wu偏pian好hao的de因yin素su之zhi一yi。味wei道dao偏pian好hao取qu決jue於yu一yi個ge複fu雜za的de互hu動dong過guo程cheng，參can與yu互hu動dong的de各ge方fang包bao括kuo味wei蕾lei、口腔和鼻腔裏的其他受體，以及所有這些受體發送給大腦的訊息。美國印第安納州西拉斐特（West Lafayette）普渡大學（Purdue University）的食品及營養學教授馬蒂斯（Rick Mattes）說，文化也發揮著一定的作用，因為人們往往會偏愛自己熟悉的食物。除此之外，多次重複有時也會讓人們培養起對特定食物的偏好：以牡蠣為例，很多人一開始都不喜歡它那種粘乎乎的口感，吃過幾次之後卻會喜歡上這種食物。
蒙內爾中心研究員、美國新澤西州新布朗斯維克（New Brunswick）羅格斯大學（Rutgers University）教授布雷斯林（Paul Breslin）說，“我們都有過這樣的經曆，那就是我們喜歡吃某種東西，人家卻覺得這種東西太粘、太滑、太澀或者太軟。正是由於這個原因，同一個產品係列當中往往會有幾種口感不同的產品”，比如帶果粒的橙汁和不帶果粒的橙汁。
蒙內爾中心的科學家們說，我們的日常食品當中，60%由(you)澱(dian)粉(fen)組(zu)成(cheng)或(huo)是(shi)加(jia)有(you)澱(dian)粉(fen)，有(you)鑒(jian)於(yu)此(ci)，要(yao)想(xiang)搞(gao)清(qing)人(ren)們(men)的(de)口(kou)感(gan)偏(pian)好(hao)，關(guan)鍵(jian)在(zai)於(yu)搞(gao)清(qing)澱(dian)粉(fen)的(de)消(xiao)化(hua)過(guo)程(cheng)。布(bu)雷(lei)斯(si)林(lin)說(shuo)，其(qi)他(ta)研(yan)究(jiu)已(yi)經(jing)表(biao)明(ming)，人(ren)們(men)偏(pian)愛(ai)滑(hua)膩(ni)的(de)口(kou)感(gan)，也(ye)喜(xi)歡(huan)那(na)些(xie)入(ru)口(kou)即(ji)溶(rong)的(de)食(shi)物(wu)，比(bi)如(ru)冰(bing)激(ji)淩(ling)和(he)巧(qiao)克(ke)力(li)。布(bu)雷(lei)斯(si)林(lin)之(zhi)所(suo)以(yi)投(tou)入(ru)目(mu)前(qian)的(de)研(yan)究(jiu)，就(jiu)是(shi)因(yin)為(wei)他(ta)對(dui)滑(hua)膩(ni)的(de)口(kou)感(gan)很(hen)有(you)興(xing)趣(qu)。此(ci)外(wai)，澱(dian)粉(fen)酶(mei)的(de)理(li)論(lun)也(ye)有(you)助(zhu)於(yu)解(jie)釋(shi)人(ren)們(men)對(dui)冰(bing)激(ji)淩(ling)和(he)酸(suan)奶(nai)酪(lao)等(deng)產(chan)品(pin)的(de)品(pin)牌(pai)偏(pian)好(hao)，因(yin)為(wei)不(bu)同(tong)品(pin)牌(pai)的(de)產(chan)品(pin)加(jia)入(ru)了(le)不(bu)同(tong)數(shu)量(liang)的(de)澱(dian)粉(fen)。
前些日子，蒙內爾的研究人員讓73名成人品嚐了一些濃度各不相同的澱粉溶液，又讓他們在60秒(miao)鍾(zhong)之(zhi)內(nei)作(zuo)出(chu)評(ping)價(jia)，看(kan)看(kan)這(zhe)些(xie)沒(mei)有(you)特(te)殊(shu)味(wei)道(dao)的(de)半(ban)透(tou)明(ming)凝(ning)膠(jiao)狀(zhuang)物(wu)質(zhi)粘(zhan)度(du)如(ru)何(he)。這(zhe)些(xie)澱(dian)粉(fen)可(ke)以(yi)在(zai)幾(ji)秒(miao)鍾(zhong)之(zhi)內(nei)溶(rong)解(jie)，具(ju)體(ti)速(su)度(du)則(ze)取(qu)決(jue)於(yu)各(ge)人(ren)製(zhi)造(zao)的(de)澱(dian)粉(fen)酶(mei)數(shu)量(liang)。
研究人員還從受試者的血樣和口腔拭子當中提取了DNA樣本，旨在確定負責製造澱粉酶的基因拷貝數和受試者報稱的澱粉溶解速度之間的聯係。負責製造澱粉酶的基因名為AMY1，研究結果表明，不同的人擁有數量千差萬別的AMY1拷貝，與此同時，AMY1拷貝比較多的受試者報稱的澱粉溶解速度也比較快。此項研究於上月發表在公共科學圖書館（Public Library of Science）的《公共科學圖書館•綜合》（PLoS ONE）雜誌上。
目前，蒙內爾中心的研究人員正在進行相關研究，目的是確定進食之後，AMY1拷kao貝bei數shu較jiao高gao的de人ren是shi否fou會hui出chu現xian較jiao高gao的de血xue糖tang峰feng值zhi。此ci外wai，研yan究jiu人ren員yuan還hai計ji劃hua找zhao出chu較jiao高gao的de澱dian粉fen酶mei產chan量liang和he食shi物wu偏pian好hao之zhi間jian的de聯lian係xi，並bing且qie假jia定ding澱dian粉fen酶mei產chan量liang較jiao高gao的de人ren將jiang會hui偏pian愛ai澱dian粉fen含han量liang較jiao高gao的de食shi品pin，因yin為wei他ta們men可ke以yi讓rang大da量liang葡pu萄tao糖tang更geng快kuai進jin入ru自zi己ji的de血xue液ye。
澱dian粉fen酶mei的de作zuo用yong和he澱dian粉fen溶rong解jie的de速su度du也ye與yu糖tang尿niao病bing有you關guan。很hen有you可ke能neng，那na些xie能neng夠gou快kuai速su消xiao化hua澱dian粉fen的de人ren更geng容rong易yi出chu現xian較jiao高gao的de血xue糖tang峰feng值zhi，這zhe樣yang一yi來lai，他ta們men的de身shen體ti就jiu必bi須xu製zhi造zao出chu更geng多duo的de胰yi島dao素su。布bu雷lei斯si林lin博bo士shi的de蒙meng內nei爾er同tong事shi、研究論文的第一作者曼德爾（Abigail Mandel）shuo，shentichangqichengshouzheyangdezhongfu，zhexierenjiukenenghuiduiyidaosuchanshengkangju，ruguoshentizhizaoyidaosudenenglizaiyalizhixiaxianyubengkui，zhexierenhaikenenghuilihuantangniaobing。
buleisilinboshishuo，dianfenmeihetuoyezhongdeqitayixie，haiyouzhuyujieshirenmendekouganpianhaoweishenmehuisuinianlingdebianhuaerbianhua。julilaishuo，xuduonianyoudehaizidoubuxihuanmouxietedingdeshuiguo，yinweitamenjiaodetamenyouzhanyouhua──比bi如ru西xi紅hong柿shi。不bu過guo，人ren們men分fen泌mi唾tuo液ye的de速su度du會hui隨sui著zhe年nian齡ling的de增zeng長chang而er衰shuai減jian。這zhe樣yang一yi來lai，他ta們men用yong嘴zui巴ba溶rong解jie澱dian粉fen的de能neng力li就jiu可ke能neng會hui受shou影ying響xiang，滑hua溜liu的de口kou感gan也ye會hui由you此ci減jian弱ruo。
