Structuring Lipids by Enzymatic Reactions

Structuring Lipids by Enzymatic Reactions

ByAnn Przybyla Wilkes 
Contributing Editor

The latest developments in the quest for functionallipids without negative health effects include oils and fats with virtually no transfats produced through enzymatic interesterification. However, it is not theuse of interesterification (the rearrangement and attachment of fatty acidsamong triglycerides) to structure lipids that is new.

Ins and outs of interesterification 

Enzymatic interesterification hasbeen in use for more than 25 years. But its commercial use, until recently, waslimited to specialty fats for infant nutrition and cocoa-butterreplacements, due to the cost of the process. Now, structured lipids producedthrough enzymatic interesterification can be found in products such asmargarines and spreads, snack cakes, cookies, and enrobed cookies.

Chemical interestification has been used even longer. In the early 1940s,chemical interesterification improved lards crystallization properties. Sincethen, additional applications include improving functional properties of oilssuchas changing the meltingpoint profile of solid fats, improving the compatibilityof different triglycerides, and changing the emulsifying properties of some oilsandchanging the nutritional properties of some edible oils, points out ErnestoHernandez, head of the fats and oils program, Texas A&M University, CollegeStation.

A drawback of chemical interestification is that it is random, althoughprocesses such as crystallization and fractionation can manipulate the processsomewhat. Chemical interesterification has five main steps: oil pretreatment, reactionwith catalyst, deactivation, post-bleaching and deodorization, explains Wim DeGreyt, De Smet Group, Belgium. Oil losses of up to 5% can occur, due to the wetcatalyst inactivation, he adds.

Enzymatic interesterification offers certain advantages over chemicalinteresterification. These include continuous process versus batch, cleaner output stock, gentlerprocess, possibility for nonrandom products and catalyst reuse, suggestsRobert (Bob) Wainwright, technical service director, Cargills Dressings,Sauces and Oils North America, Charlotte, NC.

In the past, the roadblock to widespread use of enzyme interesterificationhas been cost. This is changing, since the design of reusable, immobilizedlipases has made this process commercially viable for products other thanspecialty oils.

Taking it commercial 

Research and development work by ADM, Decatur,IL, and Novozymes A/S, Bagsvaerd, Denmark, led to the commercialization of fatsand oils produced by enzymatic interesterification in 2002. The first productwas a cocoa-butter substitute. In July 2004, a line of NovaLipid zero/low trans-fat oils and margarinesdebuted. These oils and margarines are currently produced at ADMs plants in Quincy,IL and Mankato, MN.

Initial research on the oils started about six years ago when Novozymesintroduced a new immobilized enzyme on a silica carrier.

Traditionally, the disadvantage of the enzyme process was the short lifeof the enzyme, but by increasing the life of the enzymes, the process cost goesdown, explains Mark Matlock, senior vice president, food research, ADM.

The new immobilized enzyme affects the fatty acids at the one and threeposition on the glyceride molecule. The fats produced by enzymatic interesterification are digested in the sameway as other fats, by passing through the intestine membrane as two free fattyacids and a monoglyceride with a fatty acid in the two position. Since this enzyme does not change the two position during the reaction,digestion is similar to that of noninteresterified fats.

The silica carrier has several advantages over previous carriers: it is lessexpensive, it has a high bulk density, and it allows the reaction to take placewithout water addition. This is possible because the silica holds some boundwater. Another advantage of the silica is that it is incompressible, so thecolumns used in production can be scaled up with low back pressure. Previously,it was necessary to minimize the depth of the column bed,Matlock explains.

The low- or no-trans-fat soybean oil is produced by blending anonhydrogenated soybean liquid oil with a soybean oil that has been completelyhydrogenated at an 80:20 ratio through enzymatic interesterification. Since the soybean oil is completely hydrogenated, no trans fats areproduced. However, the resulting lipid has the consistency of candle wax, and thereforerequires blending with liquid oils to obtain the desired characteristics.

The saturated fatty acid in NovaLipid is stearic acid. The World HealthOrganization, American Heart Association, and the Institute of Medicine haveconcluded that stearic acid has a neutral effect on blood LDL cholesterol basedon published studies. FDA has stated that interesterified fats containing greater than 20% stearatemay be labeled interesterified soybean oil.

Much research has taken place in response to concerns raised about the healtheffects of trans fatty acids, says Mike Rath, general manager of OleoChemical/Specialty Oils and Fats, ADM, of the timing of the research anddevelopment work. We wanted to let nutrition drive the direction of theresearch, we worked with functionality, he explains.

Moving away from trans fat 

Saturatedfatty acids are usually solid at room temperature, while unsaturated fatty acidsare soft or liquid. A look at basic lipid chemistry provides a betterunderstanding of concerns about trans fatty acids.

Fatty acids consist of chains of carbon atoms with hydrogen atoms attached tothem. A saturated fatty acid has the maximum possible number of hydrogen atomsattached to every carbon atom and, therefore, is saturated with hydrogen atoms. Also, single bonds attach all of the carbons to eachother.

In unsaturated fatty acids, at least one pair of hydrogen atoms within thechain is missing, resulting in at least two carbon atoms connected by a doublebond. A fatty acid with one double bond is called monounsaturated, while fatty acids with more than one double bond are polyunsaturated.In general, the more saturated a fatty acid is, the thicker it is.

Fats that are solids at room temperature offer functional properties thatfood product designers often require to obtain the desired texture in finishedproducts. These fats also have a longer shelf life than unsaturated fats, sincethey are less prone to oxidation than are fatty acids with double bonds.

Partial hydrogenation can increase the shelf life of vegetable oils andprovide a more-solid product by reducing the number of double bonds. Hydrogenation of vegetable oil was first launched in the United States in1910, when Procter and Gamble introduced Crisco as a lard replacement.

Vegetable oils are partially hydrogenated by bubbling hydrogen gas throughthem at very high temperatures. The resulting fat is solid at room temperature, allowing it to be used in avariety of cooking and baking applications. It also has improved oxidative stability and, therefore, improved flavor andshelf life over liquid vegetable oils.

The problem with hydrogenation is the process results in the creation of transfatty acids, which have hydrogen atoms on opposite sides of the double bond.Unsaturated fatty acids occur primarily in nature in the cis configuration.Cis fatty acids have hydrogen atoms on the same side of the carbon chainand double bond. Clinical studies have shown that trans fatty acids notonly raise LDL (bad) cholesterol like saturated fats, they also lower HDL(good) cholesterol, which increases the risk of coronary heart disease.

In 1994, the Center for Science in the Public Interest (CSPI), WashingtonD.C., filed a petition with FDA requesting that it take steps to require transfat to be listed on nutrition labels. FDA issued a final ruling on July 11,2003, requiring all food labels to display the amount of trans fat in thefood, if the total fat in the item is more than 0.5 grams per serving, by Jan.1, 2006.

FDA has estimated that by three years after the trans labelingregulation goes into effect it will have prevented 600 to 1,200 heart attacksannually and saved 250 to 500 lives annually. However, the agency is allowingfood companies to seek an extension to use existing label stock without transfats listed.

FDA also estimated that industry would incur a one-time cost of approximately$140 million to $250 million to determine the amount of trans fat in thefood products, re-label the Nutrition Facts panel to add trans fat, andreformulate products voluntarily to decrease the amount of trans fat. Theagency noted that high consumer demand for healthier oils, and the accompanyingindustry response, is a testament to the success of the agencys trans-fatlabeling rule and industrys move to using healthier oils.

Promise of improved nutrition 

In addition to the opportunity toenhance functionality, enzymatic interesterification also allows food designersto create preferred triglyceride structures from a metabolic standpoint,suggests Wainwright. The challenge is to identify the appropriate enzyme withthe desired activity, he adds.

The promise of healthier oils continues as research in this area progresses. Among the researchers in this field, Casimir C.Akoh, Ph.D., professor,department of food science and technology, University of Georgia, used enzymaticinteresterification to develop structured lipids using omega-3 oils from algaethat dont have a fishy aftertaste. The omega-3 molecule was kept at the two position for better absorption.In addition, Akoh has produced many other structured lipids for functionalityin foods such as margarine and spreads, and others for health attributes.

The possibilities of what can be accomplished with enzymaticinteresterification in the future are endless, Akoh suggests.

Ann Przybyla Wilkes is a freelance writer and communication consultant withmore than 20 years experience writing about the food industry, environmentaltopics and chemical issues. She has served as the vice president ofcommunications for the Snack Food Association and has an M.S. in Food Science. Her e-mail is: [email protected]. 

Recognition Given

The lack of trans fatin NovaLipid was partly responsible for a number of awards that ADM, Decatur,IL, and Novozymes A/S, Bagsvaerd, Denmark, received. The first of the awardscame from Frost and Sullivan Market Research. In Sept. 2004, ADM was awarded the Frost and Sullivan Product LeadershipAward in the field of edible oils and fats for the line of zero/low trans-fatoils.

The award is based on a survey of people in the edible oils and fatsindustry. Frost and Sullivan recognized that the NovaLipid products had the potentialto revolutionize the edible oils and fats sector.

Then in May 2005, the American Oil Chemists Society awarded ADM itscorporate achievement award for the commercialization of enzymaticallyinteresterified margarine and shortening fats.

The next award, issued in June 2005, recognized both ADM and Novozymes. TheU.S. Environmental Protection Agency (EPA) presented the 2005 Presidential GreenChemistry Challenge Award for the manufacturing process used to produceNovaLipid. The agency praised the environmental benefits of the process, such aseliminating the use of several harsh chemicals, eliminating byproducts and bothsolid and water waste streams, and improving the use of edible oil resources.

In announcing the award, EPA stated, Of the available strategies,interesterification is the most effective way to decrease the trans fat content in foods withoutsacrificing the functionality of partially hydrogenated vegetable oils. ADMhad produced more than 15 million pounds of interesterified oils at the time ofthe award.

The most recent award, issued Dec. 1, 2005, was the IndustryWeek Technology and InnovationAward. The award honored ADM for joining with Novozymes to develop a technologythat will prove particularly vital to food processors in light of FDAs trans-fatlabeling requirement.