Sugar – starch – and carbohydrates – Processes – Carbohydrate manufacture and refining
Reexamination Certificate
2001-12-28
2004-02-17
Bell, Mark L. (Department: 1755)
Sugar, starch, and carbohydrates
Processes
Carbohydrate manufacture and refining
C127S042000, C127S053000, C127S055000, C210S635000, C210S650000, C210S651000, C210S656000, C210S659000, C210S198200, C426S658000
Reexamination Certificate
active
06692577
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a novel process for purifying maltose-containing liquors, such as maltose syrups.
Maltose is a valuable raw material in the production of maltitol (&agr;(1→4)glucosylsorbitol), which is a sugar alcohol generally used as a sweetening agent in low-caloric, dietary and low-cariogenic foods, such as confectionary products and chewing gums. Maltitol is prepared in the form of crystalline maltitol or maltitol syrup.
Maltose is produced from a starch solution, which is first enzymatically hydrolyzed into a maltose syrup. For the production of maltitol, maltose syrup is catalytically hydrogenated to maltitol, whereafter the maltitol syrup is crystallized. The maltose syrup used as the starting material for the hydrogenation and crystallization contains varying levels of undesirable impurities, especially maltotriose. Maltotriose has a tendency to make the final maltose product unstable and hygroscopic. Furthermore, the presence of maltotriose may disturb the crystallization of maltose and maltitol. For preparing crystalline products of high purity, it is thus necessary to purify the maltose-containing syrup from maltotriose. Various methods, such as hydrolysis with enzymes, chromatography and ultrafiltration or combinations thereof have been used for the purification of maltose syrups.
An enzymatic hydrolysis method for the production of maltose has been disclosed e.g. in U.S. Pat. No. 4,408,041 (Hayashibara). Chromatographic methods for the purification of maltose have been disclosed in U.S. Pat. Nos. 3,817,787 (Suomen Sokeri Oy) and 4,487,198 (Hayashibara), for example.
Ultrafiltration for the purification of liquors containing maltose and glucose have been described e.g. in U.S. Pat. No. 4,429,122 (UOP Inc.). This U.S. Patent discloses a process for the separation of a mono- or disaccharide, such as glucose and/or maltose, from polysaccharides by passing a mixture containing monosaccharides, disaccharides and polysaccharides through an ultrafiltration membrane. Polysaccharides are retained on the ultrafiltration membrane, while monosaccharides and disaccharides are permeated through the membrane. In this process, maltose and/or glucose are separated from oligosaccharides, but not from impurities having a smaller molar mass, such as maltotriose.
U.S. Pat. No. 4,511,654 (UOP Inc.) relates to a process for the production of a high glucose or maltose syrup by treating a glucose/maltose-containing feedstock with an enzyme selected from amyloglucosidase and &bgr;-amylase to form a partially hydrolyzed reaction mixture, passing the resultant partially hydrolyzed reaction mixture through an ultrafiltration membrane to form a retentate and a permeate, recycling the retentate to the enzyme treatment stage, and recovering the permeate including the high glucose or maltose syrup. Even in this process, the resulting glucose/maltose syrup is not free from impurities, such as maltotriose.
Japanese Patent Publication JP 51098346 A (Ajinomoto KK) discloses the preparation of high purity maltose by reacting gelatinized starch with &bgr;-amylase and ultrafiltering the solution thus obtained using a semipermeable membrane having a cut-off size of 5000 to 50000 g/mol, preferably 10000 to 30000 g/mol. A highly pure maltose is obtained as the filtrate.
Nanofiltration is a relatively new pressure-driven membrane filtration process, falling between reverse osmosis and ultrafiltration. Nanofiltration typically retains large and organic molecules with a molar mass greater than 300 g/mol. The most important nanofiltration membranes are composite membranes made by interfacial polymerisation. Aromatic polyamide membranes, polysulfone membranes, sulfonated polysulfone membranes, polyether sulfone membranes, sulfonated polyether sulfone membranes, polyester membranes and polypiperazine membranes are examples of widely used nanofiltration membranes. Inorganic and ceramic membranes can also be used for nanofiltration.
U.S. Pat. No. 5,869,297 (Archer Daniels Midland Co.) discloses a nanofiltration process for making dextrose. This process comprises nanofiltering a dextrose composition including as impurities higher saccharides, such as disaccharides and trisaccharides. A dextrose composition having a solids content of at least 99% dextrose is obtained. Crosslinked aromatic polyamide membranes have been used as nanofiltration membranes.
WO 99/28490 (Novo Nordisk AS) discloses a method of producing di- and oligosaccharide syrups by enzymatic reaction of saccharides followed by nanofiltration of the enzymatically treated saccharide solution to obtain as the retentate an oligosaccharide syrup containing disaccharides and higher saccharides. A thin film composite polysulfone membrane having a cut-off size less than 100 g/mol has been used as the nanofiltration membrane, for example. In one embodiment of the process, a liquefied starch solution of maltodextrins is used as the starting material for the enzymatic reaction and subsequent nanofiltration.
U.S. Pat. No. 6,126,754 (Roquette Freres) relates to a process for the manufacture of a starch hydrolysate with high dextrose content. In this process, a starch milk is subjected to enzymatic treatment to obtain a raw saccharifed hydrolysate. The hydrolysate thus obtained is then subjected to nanofiltering to collect as the nanofiltration permeate the desired starch hydrolysate with a high dextrose content.
BRIEF DESCRIPTION OF THE INVENTION
The purpose of the present invention is to provide a method for purifying a maltose-containing liquor from maltotriose using membrane filtration techniques. The process of the claimed invention is based on the use of nanofiltration.
In accordance with the present invention, complicated and cumbersome purification methods, such as chromatographic steps can be completely or partly replaced by less complicated nanofiltration membrane techniques. The process of the present invention can provide a maltose solution essentially free from undesired low molar-mass impurities, such as maltotriose.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a process for purifying a maltose-containing liquor from maltotriose, wherein said maltose-containing liquor has a maltose content of at least about 55% by weight, based on dissolved dry solids, by nanofiltering said liquor and recovering as the permeate a maltose solution having an increased ratio of maltose to maltotriose.
In a typical embodiment of the invention, the process comprises recovering a maltose solution having a ratio of maltose to maltotriose of over 1.1 times, preferably over 5 times, more preferably over 10 times and most preferably over 20 times that of the starting liquor. Typically, the process comprises recovering a maltose solution having a ratio of maltose to maltotriose of 1.1. to 30 times, preferably 5 to 30 times, more preferably 10 to 30 times and most preferably 20 to 30 times that of the starting liquor.
The maltose content of the starting liquor is at least about 55% by weight, preferably at least about 80% by weight, based on dissolved dry solids. The maltose content is typically in the range of 55 to 90%, preferably 80 to 90% by weight, based on dissolved dry solids.
The separation of maltose from maltotriose can be regulated by varying the maltose content of the starting maltose-containing liquor.
The maltose-containing liquor to be treated by the process of the invention may be a maltose syrup, for example.
The dry substance content of the starting maltose-containing liquor is typically 5 to 50% by weight, preferably 8 to 25% by weight.
The maltose-containing liquor used as the starting material usually contains also monosaccharides, mainly glucose, in a typical amount of 10 to 95%, based on the maltose content. The starting liquor may also contain minor amounts of other monosaccharides. Furthermore, the starting maltose-containing liquor typically contains oligosaccharides and small amounts of ionic compounds, such as metal cations, e.g. sodium, potassium, calcium, magnesium and iron cations.
The malt
Heikkilä Heikki
Lindroos Mirja
Mänttäri Mika
Nyström Marianne
Bell Mark L.
Danisko Sweeteners Oy
Hailey Patricia L.
Scully Scott Murphy & Presser
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