crystalline fructose
natural sources of fructose include fruits, vegetables (including sugar cane), , honey. fructose further concentrated these sources. highest dietary sources of fructose, besides pure crystalline fructose, foods containing table sugar (sucrose), high-fructose corn syrup, agave nectar, honey, molasses, maple syrup, fruit , fruit juices, these have highest percentages of fructose (including fructose in sucrose) per serving compared other common foods , ingredients. fructose exists in foods either free monosaccharide or bound glucose sucrose, disaccharide. fructose, glucose, , sucrose may present in food; however, different foods have varying levels of each of these 3 sugars.
the sugar contents of common fruits , vegetables presented in table 1. in general, in foods contain free fructose, ratio of fructose glucose approximately 1:1; is, foods fructose contain equal amount of free glucose. value above 1 indicates higher proportion of fructose glucose, , below 1 lower proportion. fruits have larger proportions of fructose glucose compared others. example, apples , pears contain more twice free fructose glucose, while apricots proportion less half fructose glucose.
apple , pear juices of particular interest pediatricians because high concentrations of free fructose in these juices can cause diarrhea in children. cells (enterocytes) line children s small intestines have less affinity fructose absorption glucose , sucrose. unabsorbed fructose creates higher osmolarity in small intestine, draws water gastrointestinal tract, resulting in osmotic diarrhea. phenomenon discussed in greater detail in health effects section.
table 1 shows amount of sucrose found in common fruits , vegetables. sugarcane , sugar beet have high concentration of sucrose, , used commercial preparation of pure sucrose. extracted cane or beet juice clarified, removing impurities; , concentrated removing excess water. end-product 99.9%-pure sucrose. sucrose-containing sugars include common table white granulated sugar , powdered sugar, brown sugar.
^a carbohydrate figure calculated in usda database , not correspond sum of sugars, starch, , dietary fiber .
all data unit of g (gram) based on 100 g of food item. fructose/glucose ratio calculated dividing sum of free fructose plus half sucrose sum of free glucose plus half sucrose.
fructose found in synthetically manufactured sweetener, high-fructose corn syrup (hfcs). hydrolyzed corn starch used raw material production of hfcs. through enzymatic treatment, glucose molecules converted fructose. there 3 types of hfcs, each different proportion of fructose: hfcs-42, hfcs-55, , hfcs-90. number each hfcs corresponds percentage of synthesized fructose present in syrup. hfcs-90 has highest concentration of fructose, , typically, used manufacture hfcs-55; hfcs-55 used sweetener in soft drinks, whereas hfcs-42 used in many processed foods , baked goods.
carbohydrate content of commercial sweeteners (percent on dry basis)
data obtained kretchmer, n. & hollenbeck, cb (1991). sugars , sweeteners, boca raton, fl: crc press, inc. hfcs, , usda fruits , vegetables , other refined sugars.
cane , beet sugars have been used major sweetener in food manufacturing centuries. however, development of hfcs, significant shift occurred in type of sweetener consumption in countries, particularly united states. seen in figure 3, change happened in 1970s. contrary popular belief, however, increase of hfcs consumption, total fructose intake relative total glucose intake has not dramatically changed. granulated sugar 99.9%-pure sucrose, means has equal ratio of fructose glucose. commonly used forms of hfcs, hfcs-42, , hfcs-55 have equal ratio of fructose glucose, minor differences. hfcs has replaced sucrose sweetener. therefore, despite changes in sweetener consumption, ratio of glucose fructose intake has remained relatively constant.
figure 3: adjusted consumption of refined sugar per capita in us
nutritional information
providing 368 kcal per 100 grams of dry powder (table), fructose has 95% caloric value of sucrose weight. fructose powder 100% carbohydrates , supplies no nutrients in significant content (table).
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