Đề tài production of fructose syrup from jerusalem artichoke

PRODUCTION OF FRUCTOSE SYRUP FROM JERUSALEM ARTICHOKE Chapter 1: SUPERVISOR: VAN VIET MAN LE Introduction I Production of fructose syrup in the world: Sweeteners have enhanced our enjoyment of food for thousands of years Honey was the principal sweetener in the human diet until sucrose became available after the Crusades Both honey and sucrose comprise nearly equal parts fructose and dextrose (glucose) The monosaccharides are free in honey, but linked together through a glycosidic bond in the disaccharide sucrose Starch is a storage polymer of dextrose in many cereals, grains and vegetables The discovery that starch polymers could be depolymerized to sweet monomer subunits made dextrose an attractive alternative to sucrose for some applications However, lower relative sweetness coupled with unique physical properties and functionality left dextrose an imperfect replacement for sucrose in many food and beverage products Concurrent advances in refining, isomerization and separation technologies in the 1960s made possible the production form corn starch of high-fructose syrup (HFS) with sweetness equivalent to sucrose Ease of handling this liquid sweetener and lower price accelerated the acceptance of HFS by food and beverage producers PRODUCTION OF FRUCTOSE SYRUP FROM JERUSALEM ARTICHOKE SUPERVISOR: VAN VIET MAN LE Although sucrose from sugar beets and starch from rice, wheat, tapioca and potato are used in the manufacture of HFS throughout the world, corn (maize) is by far the starch most widely used for this purpose Its abundance and agricultural stability combine to make corn starch a low-cost raw material for the production of HFS in many countries Manufacturing of high-fructose corn syrup (HFCS): The production of HFCS required the following manufacturing steps:  Wet milling corn to extract the starch  Saccharification and liquefaction to hydrolyze polymer starch to monomer dextrose  Isomerization to convert dextrose to fructose  And fractionation to enrich the concentration of fructose in isomerization product stream 1.1 Corn wet milling: Corn is abundant source of starch Starch comprises >60% of the total weight of the corn kernel (>70% on a dry basis) A high-molecular-weight polymer of dextrose, starch is stored in granules within the endosperm of the kernel The objective of wet milling process is to separate starch from other corn by-products likes protein, oil and fiber PRODUCTION OF FRUCTOSE SYRUP FROM JERUSALEM ARTICHOKE SUPERVISOR: VAN VIET MAN LE 1.1.1 Steeping: Shelled corn is slurried (steeped) up to days in warm (520C) water containing a low concentration of sulfur dioxide SO2 (0.01 – 0.02%) in preparation for milling During this time the corn hull softens, the protein (gluten) matrix anchoring starch granules in place is denatured, and soluble sugars and nutrients in the kernel diffuse into steep water SO2 is an effective protein denaturant and also functions to restrict microbiological fermentation 1.1.2 Germ separation: The embryonic, oil-rich portion of the kernel is called the germ; it is the first by-product to be recovered Steeped corn is dewatered and the passed through coarse grinding mills to break the kernel and free the germ When broken kernels are reslurried, the loosened germ separates from the rest of kernel because of its low relatively buoyant density Separation is completed either with flotation tanks or hydroclone separators 1.1.3 Fiber separation: Free fiber (corn hull) is removed from starch and gluten by using wire screens Roughly onethird of the starch separation remains bound to the fiber however, and requires gentle buffeting in a disc mill to free it Starch is recovered from the milled slurry by further washing and screening 1.1.4 Starch separation: Protein, starch and residual corn solubles are all that remain in the slurry after fiber is removed The difference in buoyant density between starch and protein is exploited to separate these components by using “mud” centrifuges (so named because of the proteinaceous sludge that separates from the starch) Nearly 95% of the protein is recovered from this step 1.1.5 Washing: Starch washing is the final step in the milling process It reduces residual impurities in the starch slurry through a series of washing and hydroclone centrifuge steps The resultant starch slurry is of sufficient purity to serve as the starting material for fructose syrup refining PRODUCTION OF FRUCTOSE SYRUP FROM JERUSALEM ARTICHOKE 1.2 SUPERVISOR: VAN VIET MAN LE Hydrolysis: Converting starch to dextrose (glucose) is the aim of this operation The more efficient conversion, the higher product yield is Thus, hydrolysis is one of the important steps affects on processing economy 1.2.1 Gelatinization: Starch granules expand its volume under heating The viscosity significantly increases and gets to the maximum value People can use mineral acid or thermostable amylase to assist the first period of the hydrolysis They will exert on the substrates (starch granules) and produce dextrin As a result, viscosity of the suspension decreases 1.2.2 Liquefaction: After gelatinization, if we continue to heat the mixture to temperature more than 1000C Texture of starch is destroyed Amylose and amylopectin are released Starch can now “soluble” on water 1.2.3 Saccharification: Glucoamylase completes the enzymatic hydrolysis of di- and oligomeric products of amylase by breaking the 1,4 and 1,6 bonds that join consecutive dextrose units Dextrose produced by the proper combination of acid and/or enzymes exceeds 95% and provides an excellent substrate for isomerization PRODUCTION OF FRUCTOSE SYRUP FROM JERUSALEM ARTICHOKE 1.3 SUPERVISOR: VAN VIET MAN LE Isomerization: The next major refining step in producing HFS is the isomerization of dextrose to fructose Lobry de Bruyn and van Ekenstein demonstrated in 1895 that dextrose is isomerized to fructose via an enediol intermediate Whereas alkali (e.g sodium hydroxide) will isomerize dextrose to fructose, this catalyst produces unacceptably high color and flavor with low fructose yield, and is not commercially viable This is due in large measure to the lability of the fructose molecule and its susceptibility to degradation under these rather harsh conditions Early attempt to enzymatically isomerize dextrose to fructose were hampered by the complex biochemical pathway linking the two sugars and the expense in regenerating essential cofactors Akabori et al discovered a glucose isomerase (actually a xylose isomerase with affinity both for dextrose and xylose) able to catalyze the conversion of dextrose to fructose without the need for cofactor regeneration Takasaki et al greatly improved the economics of enzyme catalysis by immobilizing the enzyme 1.4 Fractionation: The amount of fructose enzymatically produced from dextrose at 600C, a practical processing temperature, is restricted by an equilibrium constant of Theoretically, the highest fructose yield possible from the 94% dextrose feed stream is 47% at equilibrium Manufacturing plants typically settle for yields