MARGARINE | Methods of Manufacture

MARGARINE/Methods of Manufacture

and the number of crystals. In cases of exaggerated crystal growth, there is the hazard of increased susceptibility to microbial spoilage. The development of extremely coarse fat crystals may squeeze liquid oil from the product and allow partial coalescence of the aqueous phase. Free moisture on the surface may result in mold growth. (See Spoilage: Molds in Spoilage.) Flavor 0025

The stability of margarine flavor is enhanced by refrigerated storage to retard autoxidation of the oil and by lightproof packaging to avoid photooxidation. Changes by either mechanism produce offflavors in oils which are variously described as beany, painty, or fishy. The trend to greater use of soft margarines with higher proportions of liquid oil increases the risk of autoxidation, particularly when the oils used are high in unsaturated fatty acids. The addition of antioxidants is permitted to reduce this hazard. Photochemical oxidation of liquid oils has been shown to be greater at short wavelengths, with a maximum below 455 nm. As fluorescent light in supermarkets may transmit wavelengths between 350 and 750 nm, packaging impervious to low-wavelength light is highly recommended for maximum margarine flavor protection. (See Antioxidants: Natural Antioxidants, Synthetic Antioxidants.) See also: Antioxidants: Natural Antioxidants; Synthetic Antioxidants; Colloids and Emulsions; Emulsifiers: Organic Emulsifiers; Preservation of Food; Sensory Evaluation: Sensory Characteristics of Human Foods; Appearance; Texture; Taste; Spectroscopy: Nuclear Magnetic Resonance; Spoilage: Bacterial Spoilage; Molds in Spoilage; Vegetable Oils: Oil Production and Processing

Further Reading Chrysam M (1985) Table spreads and shortenings. In: Applewhite TH (ed.) Bailey’s Industrial Oil and Fat Products, vol. 3, pp. 41–127. New York: John Wiley. deMan JM, Dobbs JE and Sherman P (1979) In: Sherman P (ed.) Food Texture and Rheology, pp. 43–54. London: Academic Press. Heick WH (1991) A Propensity to Protect: Butter, Margarine and the Rise of Urban Culture in Canada, pp. 1–163. Waterloo, Canada: Wilfred Laurier Press. Hellemann U, Tuorila H, Lampi A-M and Matuszewska I (1990) Hedonic responses and attitudes related to fats used as spreads on bread. Food Quality and Preference 2: 29–38. Juriaanse AC and Heertje I (1988) Microstructure of shortenings, margarine and butter – a review. Food Microstructure 7: 181–188.

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Lee WE (1986) A suggested instrumental technique for studying dynamic flavor release from food products. Journal of Food Science 31: 249–250. Mela DJ and Marshall RJ (1992) Sensory properties and perceptions of fats. In: Mela DJ (ed.) Dietary Fats: Determinants of Preference, Selection and Consumption, pp. 43–47. London: Elsevier. Rohm H and Raaber S (1991) Hedonic spreadability optima of selected edible fats. Journal of Sensory Studies 6: 81–88. Vaisey-Genser M, Vane BK and Johnson S (1989) Graininess, crystal size and firmness of stored canola margarines. Journal of Texture Studies 20: 347–361. Vaisey-Genser M and Vane BK (1995) Sensory evaluation of margarine. In: Warner K and Eskin NAM (eds) Methods to Assess Quality and Stability of Oils and Fat-containing Foods, pp. 76–106. Champaign, IL: AOCS Press. van Alphen J (1969) Hippolyte Me`ge-Mouries. In: van Stuyvenberg JH (ed.) Margarine – An Economic, Social and Scientific History 1869–1969, pp. 6–8. Liverpool, UK: Liverpool University Press.

Methods of Manufacture R A Carr, Carr & Associates, Burlington, Ontario, Canada M Vaisey-Genser, The University of Manitoba, Manitoba, Winnipeg, Canada This article is reproduced from Encyclopaedia of Food Science, Food Technology and Nurtition, Copyright 1993, Academic Press.

Background Consumers have grown to appreciate the margarine products that spread easily at refrigerator temperatures and are enjoyed because of their flavor and texture. To understand the dynamics of the manufacture of these margarines, it is essential to appreciate the relationships between the processing effects, the specific physical properties of the products, and the composition of their oil blends and other components. A major factor in the formulation and control of margarine oils and margarine is the development of desirable solids-to-liquid ratios, achieved by hydrogenation and blending. The types of oils selected for margarine oil formulations are also important in obtaining a stable, uniform crystal structure from specific conditions for processing the oils, as well as the finished margarine products. As a result, margarines as semisolid plastic products in soft tub and wrapped stick forms have been designed to meet consumer demands for health and dietary benefits, as well as performance and convenience.

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A margarine structure is a network of small fat crystals, which acts as a matrix to contain trapped oil and water globules. The degree of finished product spreadability depends considerably upon the proportion and properties of the liquid oil and crystalline fat in the margarine oil component. Butter and stick margarines, for example, are brittle when cold from the refrigerator. They gradually become more spreadable as they approach room temperature, because some of the fat crystals melt as the margarine becomes warmer. Consumers desiring spreadability from the refrigerator may select soft tub margarines, which are designed with lower solids and higher liquid oil contents. Various combinations of hydrogenation, fractionation, interesterification, and blending of diverse oil types and solids contents allow the development of margarines with differing consistencies and properties. (See Colloids and Emulsions.) Margarine consumers fall into two main classifications, each with specific quality requirements. The domestic cook requires a product for table use as well as baking and frying. The professional baker demands products that will give a consistent performance for cakes, icings, etc. For the home, a margarine must provide an enjoyable flavor that releases fully and quickly, must melt rapidly in the mouth leaving no gummy or gritty sensation, have sufficient body at room temperature to maintain its form, and must be easy to spread over a broad range of temperatures. Creamability, which is the ability to take up air when beaten, and plasticity are the key priorities required for satisfactory baking. For frying, the fat component must remain stable at high temperatures and contain virtually no free fatty acids, which create a smoking problem during drying. The physical properties of various margarines depend primarily upon (1) the melting point of the oil component triglycerides, (2) the total solids content present at any given temperature, (3) the distribution of these solid fats over a broad temperature range, and (4) the polymorphic modification of crystal habit of the fat composition. Their combined response to temperature and work applied by external forces is the most characteristic. Margarine is designed to meet flavor, plasticity, and creamability requirements by combining a properly designed margarine basestock with an aqueous phase blend so that the water globules are finely dispersed, but combined loosely enough for the emulsion to break easily upon melting. The aqueous phase generally consists of reconstituted milk powder, brine, and water. Vitamins, coloring, and flavoring agents are included, and emulsifiers, such as monoglycerides and lecithin, are

added to the oil phase. (See Triglycerides: Structures and Properties.)

Formulation To ensure the development of a proper margarine emulsion prior to the crystallization process, two distinct phases, aqueous and oil, must be prepared individually, prior to blending (Figure 1). The composition of the phases is designed for the three basic types of margarines: (1) stick or regular margarine, (2) soft or tub margarine, and (3) diet or caloriereduced margarine. Diet margarines contain half as much margarine oil as the stick or tub margarines. Because of their higher water content, they are unsatisfactory for cooking purposes, but are used for spreading on bread by consumers interested in their lower energy content.

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Aqueous Phase

The major component in the margarine aqueous phase is either sweet skim milk or water plus reconstituted skim milk powder, or even water without milk if required. Care is taken that the milk is properly pasteurized by rapid heating to 75  C with sufficient contact time. If desired, cultured milk, which has had some of the lactose content converted to lactic acid, may be used to provide a distinct flavor and acidity to the milk. Salt, or brine, is then added to the aqueous phase to accentuate the flavor, act as a microbial inhibitor, and reduce splattering during pan frying. Minor components in the aqueous phase include citric acid, ethylenediaminetetraacetic acid (EDTA) and a water-soluble dairy flavor. Citric acid reduces the pH of the liquid phase to approximately 5.3, to enhance the performance of the microbial inhibitor. EDTA acts as a chelating agent by tying up any metal ions picked up either in the equipment or from other components added to the aqueous phase. (See Acids: Natural Acids and Acidulants.)

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Oil Phase

The main component in the oil phase is a margarine oil basestock specifically developed through the refining process to produce a final margarine with the appropriate flavor, keeping quality and melting characteristics necessary to produce a specific margarine with distinctive characteristics demanded by the consumer. Oil basestocks originate from crude oils such as soyabean, palm, corn, cottonseed, sunflower, canola, and rapeseed. Initial processing through refining and bleaching operations removes impurities from the oil. Refined–bleached oils can be modified

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Culture tanks Oil storage

Milk, salt Emulsifying agent Blending and weighing

Oil and oil-soluble ingredients Blending and weighing

Emulsion mix tank

Votator supply tank

Votator A unit

Pump

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Votator B unit

Wrapping and cartoning

Votator print molder To loading platform

Figure 1 Simplified flow diagram for continuous margarine solidification. Courtesy of the Girdler Co. Reproduced from Margarine: Methods of Manufacture, Encyclopaedia of Food Science, Food Technology and Nutrition, Macrae R, Robinson RK and Sadler MJ (eds), 1993, Academic Press, with permission.

by a hydrogenation process to alter their physical properties, such as melting characteristics and stability. Additional changes in the physical properties can be obtained by blending different oils and interesterification. (See Ground Nut Oil; Palm Oil; Vegetable Oils: Oil Production and Processing.) Changes to the physical properties, or hardness, of a fat can be measured by melting points, dilatometry, and nuclear magnetic resonance (NMR). Dilatometry is based on the difference in specific volume for liquid and solid fats at a specific temperature. Dilatometric curves may be plotted for solid fat indices (SFIs) against the temperature of determination. NMR provides a different approach to the determination of solids in fats and their blends. The results are determined in absolute solids terms and are utilized to provide a relatively simple technique for determining SFI curves, which are somewhat comparable with the dilatometric method. (See Spectroscopy: Nuclear Magnetic Resonance.) Most vegetable oils are mainly liquid at room temperature. Therefore, hydrogenation plays a key

role in the preparation of basestocks with various SFI melting curves that can be blended for the preparation of margarine basestocks. Other techniques such as fractionation, interesterification, directed interesterification, and corandomization, are also available, but are normally used for specific situations related to oil availability and for products requiring a distinctive melting property, such as bakery margarines. Liquid unsaturated oils have a relatively high number of double bonds, melt at low temperatures, are more unstable, and are likely to deteriorate over time in terms of odor and flavor. Treatment of the oil in hydrogenation convertors with a nickel catalyst at high temperature with violent agitation, in contact with a flow of tiny hydrogen bubbles, will insert hydrogen into some of the double bonds. Approximately 0.01% catalyst and 200  C temperature are required for margarine oil basestocks. As the process proceeds, the melting point characteristics of the oil are increased. They are measured by a refractometer in the plant and confirmed precisely in the laboratory by dilatometric or NMR analyses. When the proper

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end points are obtained, the oil in the convertor is cooled and then carefully filtered to remove all traces of catalyst. Hydrogenation is the most flexible single process for producing margarine basestocks. Depending upon the operating conditions selected, the SFI curve can be steepened or flattened by adjustment of hydrogenation temperature, pressure, agitation, catalyst type, and catalyst concentration. For example, selective hydrogenation conditions using a high temperature and lower pressure are utilized to promote high trans fatty acid development with a minimum drop in iodine value, to produce steep solids curves. Recently, some nutritionists have expressed concern over the effect of trans fatty acids on health. If ultimately confirmed. Other techniques, such as enzymatic reactions, can be utilized to provide basestocks with steep melting curves and low trans fatty acid content. Differing from shortenings, margarine oil blends are formulated to have a sufficient solids content at room temperature to perform as a stick margarine or tub margarine on the table, without slumping. At refrigerator temperature, the solid content should be kept at a minimum to ensure smooth, easy spreadability on bread when used directly from the refrigerator. In addition, margarines should melt very rapidly at body temperature (37  C) to ensure a ‘quick get away’ in the mouth with minimum gumminess. This rapid melting characteristic is attained from the development of trans fatty acids during hydrogenation, which start to melt rapidly as the temperature is increased above about 25  C. Opposite to the sharp melting curve required for a margarine, shortenings are formulated to produce flat melting curves, with very little change in solid content, from room temperature to temperatures well above body temperature. (See Fatty Acids: Properties.) In addition to the solids content curve, a second important factor in margarine oil blends is their palmitic acid content (C16:0), which has a definite effect on the crystal stability of the final margarine. Oil blends with insufficient palmitic acid content tend to revert from the b0 crystal state to an undesirable b crystal state during storage of the packaged product. b0 crystals produce both margarines and shortenings with a smooth uniform texture, because of the small size of the crystals, from 1 to 3 mm. However, b crystals are larger than 20 mm in size and produce obvious grainy texture and brittleness in margarines and shortenings. b crystal margarines are readily detected by the tongue as an undesirable gritty feel. Oils/fats that are b-tending include canola, cocoa butter, coconut, corn, lard, olive, palm kernel, peanut, safflower, sesame, soya bean and sunflower. b0 Types are cotton seed, herring, milk fat, modified lard, palm and

tallow. It is normal practice to blend approximately 5–15% of cotton seed or palm oil in margarine oil blends to minimize all possibilities of crystal conversion to the b form. Some margarine manufacturers use a larger number of different hardstock fractions also to minimize the possibilities of b crystal development. A crystal inhibitor such as sorbitan tristearate can add crystal stability insurance more effectively than diglycerides. Final margarine oil blends are carefully formulated to produce the desired solids melting curve. For example, stick margarine solids contents are approximately 27% at 10  C, 14.2% at 21.1  C, and 2.5% at 33.3  C. Soft or tub margarines, with improved spreadability characteristics, are approximately 13% (SFI) at 10  C, 7% at 21.1  C, and 2.3% at 33.3  C. The stick margarine SFI profile provides sufficient solids at 10  C to allow satisfactory parchment overwrapping during packaging, satisfactory spreadability at both room temperature and out of the refrigerator, plus a good ‘get away’ in the mouth. The margarine oil blend is then deodorized at about 250  C under a vacuum of 6 mmHg for 40 min to remove flavor and odor components, prior to its use in the margarine oil phase. The oil phase is made up separately from the aqueous phase. Sufficient oil is pumped into the blend tank to ensure that the final product will have an oil content of 80% in the final stick or tub margarine, or 40% for low-energy diet spreads. Approximately 0.2% lecithin is metered into the oil as an emulsifier and antispattering agent during pan frying. Food coloring and oil-soluble butter flavor (0.05% of each) are added, and vitamins A and D are included for nutritional purposes. Margarine flavor release can be affected by the ‘tightness’ of the final oil/aqueous emulsion. Tight emulsions reduce the flavor impact as compared with loose emulsions. Therefore, phase blending and crystallization practices need to be carefully controlled to ensure uniform flavor release characteristics. (See Cholecalciferol: Properties and Determination; Colorants (Colourants): Properties and Determination of Natural Pigments; Properties and Determinants of Synthetic Pigments; Emulsifiers: Organic Emulsifiers; Uses in Processed Foods; Retinol: Properties and Determination.)

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Crystallization Immediately prior to the packaging of margarine, the liquid and oil phases are mixed together in a 1:4 ratio, with gentle agitation, and maintained at about 40  C. The temperature is selected to develop a stable emulsion and to prevent any precrystallization, which would occur at temperatures below 37  C. A

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proper emulsion will have the water phase droplets finely dispersed in the oil phase, but loosely enough for the emulsion to break easily on melting. Margarine emulsions can be made by either a batch or continuous system. The batch system has been used for many years and comprises an agitated, temperature-controlled mixing tank to receive the water and oil phases. After the batch has been mixed to form a stable emulsion at the required temperature, the emulsion is then pumped to a scraped-surface heat exchanger for supercooling. The batch system is usually used for operations required to produce many different types of margarines with production runs of relatively short duration. In lieu of a mixing tank, the continuous system may use a three-headed proportioning pump to meter and mix the oil phase continuously and the water phase simultaneously in the proper proportions into an agitated, temperature-controlled holding tank and then directly to the scraped-surface heat exchanger. The continuous system is designed for plants that run large quantities of similar types of margarines over extended time periods. A scraped-surface heat exchanger is a unit that adds heat or removes heat from a substance. In the margarine industry, it is used as a closed chilling machine that induces partial crystallization of the fat in the margarine emulsion, all taking place in stainless steel, externally refrigerated cylinders through which the fat is pumped continuously. The cylinders are equipped with fast-revolving scraper blades that work the fat to achieve efficient, even heat transfer to the total mass in the heat exchange tubes. The process, if desired, can be utilized to add air or gas to a margarine, for the production of whipped margarines. In the industry, the process is often called ‘votation,’ because the original units were produced by the Votator Division of the Chemetron Corporation, Louisville, Kentucky. The objective of votation is to develop and seed b0 crystals throughout the margarine, to ensure their progression to the dominant crystal form in the finished product. If successful, the margarine will then have a smooth textural feel on the tongue, as well as contributing to a smooth-spreading performance on bread. For long-term uniform production, attention must be paid to the sharpness of votator blades and the smooth condition of the chilling cylinders. For margarine, the votator should rapidly reduce the incoming emulsion temperature from about 40 to 7  C. The votator, also called an ‘A unit,’ is designed for direct-expansion refrigerants such as ammonia, freon, and propane. Advantage is taken of its high rate of heat transfer due to ‘surface boiling.’ A considerable proportion of the liquid vaporizes upon

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contact with the heat-transfer tube, and the velocity of the gas carries a relatively high percentage of liquid ammonia back to the surge drop, thus assuring complete flooding of the heat-transfer surface at all times. As a result, a constant uniform chilling effect is achieved for margarine passing through the chilling cylinder. The emulsion is worked through the chilling cylinder over a period of about 18 s. Supercooled product leaving the A unit is then pumped to the ‘B unit’ cylinder, which is considerably smaller in diameter and longer than the B unit used for shortenings. In addition, the margarine B unit is not agitated, so that solidification of the supercooled margarine emulsion takes place under almost static conditions. If desired for whipped margarine, air or preferably an inert gas such as nitrogen can be drawn into the emulsion at the suction side of the product pump in precise amounts regulated by flow meters as it is fed to the chilling unit. Limiting the amount of work given to the product in the B unit (1) produces a product that is not too soft to be handled in automatic print forming and wrapping equipment, (2) prevents the aqueous phase from being dispersed in a too fine state of suspension, and (3) induces the growth of b0 seed crystals from the supercooled mass. Agitation in the B unit would require a long ‘dwell period’ for the product to become firm enough for packaging. In addition, the resultant tight emulsion and incorrect crystal structure would delay melting of the product in the mouth, producing a waxy impression with the user. Tight emulsions also fail to yield the desirable milk and salt flavors before the product has been swallowed, and contribute to brittleness or hardness, which is reflected in the lack of spreadability at refrigerator temperatures. While the product is in the B unit, the temperature rises by approximately 5  C, primarily due to the latent heat of crystallization. The supercooled mass solidifies as it is slowly forced through the B unit by the pressure of the feed pump. After leaving the B unit, the finished stick margarine product is extruded in a rectangular form, shaped, and wrapped. For many print margarines, a combination of vegetable parchment paper and aluminum foil is often used to make a final print product in a unit such as the Benhil. Popular soft margarines are continuously packed in tubs usually made from polyvinylchloride. The filled product is then automatically packed into cases, sealed, and sent to a tempering room. Packaged margarines should be stored at 5–10  C for 48 h before shipment from the warehouse. This will ensure that the desired b0 crystals have sufficient time to multiply and reach a stable state.

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Quality Assurance

Further Reading

During production, it is important to carry out an ongoing routine inspection of processing conditions and finished product. The former includes items such as the A unit outlet temperature, which must be frequently checked, adjusted, and recorded by the operator. Product evaluations are usually carried out by the quality control inspectors and laboratory technicians. (See Quality Assurance and Quality Control.) Samples from the packing lines are taken every 15–30 min and checked for weight performance versus limits for each product type. Line samples are then checked for package quality, including: carton or container denting or crushing; dirt or oil spots; parchment wrap defects for stick margarine, such as poor folds of the parchment or foil; inadequate gluing of carton inflaps; improper placement of lable. Packaging materials are then removed, and the product’s external appearance is evaluated. Prints are sliced in two or three places for internal examination, and a cone can be cut out of the center of the tub products. The outer texture is checked for slack or overfill, sloshing, product adhering to the lid or wrap, blistered or grainy texture, discoloration, oil separation, dull sheen, etc. After cutting, the inner texture is checked for oil or water separation and streaked, grainy, vacillated, cheesy, or porous texture. Margarines undergo sensory evaluation to detect any off-quality characteristics, such as lack of flavor, or oil off-flavors such as oxidized, rancid, faulty oil processing, sour, plastic, fruity, artificial, and aged characteristics. If required, quality-rating systems can be established with defect scores assigned by the importance of the defect for the product. For example, a 100-point scale could be used, with 10 points assigned to packaging and 30 points each for outer texture, inner texture, and flavour. The assigned defect points are then subtracted from 100. A grade below an arbitrary level such as 70 would indicate that the related product should be placed on hold for further evaluation and disposition. (See Sensory Evaluation: Sensory Characteristics of Human Foods.)

Carr R (1986) Oilseeds, fat and oils. National Research Council Training Program, Chatham, Ontario, pp. 10–14. Dritschel M (1970) How to evaluate margarine quality. Food Engineering, October: 90–93. Krytz K (1989) Formulation and packaging margarines and shortenings. Annual Meeting of the American Oil Chemists’ Society, Cincinnali, Ohio, May 3–6, 1989. Journal of the American Oil Chemists Society 66(4): 459–460. Moore E (1974) Margarine and cooking fats. Unilever Educational Booklet Series, No. 4, pp. 7–14. Ward J (1988) Processing canola oil products. Journal of the American Oil Chemists Society 65: 1731–1734. Wiederman L (1978) Margarine and margarine oil, formulation and control. Journal of the American Oil Chemists Society 55(11): 823–829.

See also: Acids: Natural Acids and Acidulants; Cholecalciferol: Properties and Determination; Colloids and Emulsions; Colorants (Colourants): Properties and Determination of Natural Pigments; Properties and Determinants of Synthetic Pigments; Emulsifiers: Organic Emulsifiers; Uses in Processed Foods; Fatty Acids: Properties; Quality Assurance and Quality Control; Retinol: Properties and Determination; Spectroscopy: Nuclear Magnetic Resonance; Triglycerides: Structures and Properties; Vegetable Oils: Oil Production and Processing; Sensory Evaluation: Sensory Characteristics of Human Foods; Ground Nut Oil

Composition and Analysis M Vaisey-Genser, The University of Manitoba, Winnipeg, Manitoba, Canada Copyright 2003, Elsevier Science Ltd. All Rights Reserved.

Introduction Margarine is the earliest of the designed food staples. As such, it can be tailored to deliver nutritional and functional advantages in terms of fatty acid composition, the addition of essential micronutrients, spreadability, and performance as a bakery fat. Accurate methods are necessary to guide margarine design and to monitor the legitimacy of claims on margarine labels. This article will describe the required composition of margarine, provide examples of the fatty acid profiles of contemporary products, and comment on the methods for margarine analysis and quality control.

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Margarine Composition The margarine of each country is subject to local standards of identity and regulations, which normally complement the international standard of the Joint FAO/WHO Food Standards Programme as set by the Codex Alimentarius Commission. The existing standard for margarine as set in 1989 (CODEX STAN 32-1981, Rev. 1-1989) is currently under review. Ultimately, it is to be replaced by a general ‘Standard for Fat Spreads and Blended Spreads,’ a proposal being drafted to address reduced-fat as well as fullfat spreads. The goal is to assure food safety concurrent with the globalization of food trade. As of July 1999, the draft proposal was at Step 3 of what can be

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