Ingriedients of Low Fat Spreads

The technology of low-fat spread manufacture has two salient aspects: Selection of ingredients, and processing. The important constituents of spreads are fat, (milk) proteins, stabilizers, emulsifiers, emulsifying salts, acidulants, common salt, colouring and flavouring materials, vitamins, preservatives/ antioxidants, etc. Each ingredient has specific importance in production of a good-quality spread.

 

i. Fats and Oils

Fat is a major ingredient of a low-fat spread. The main functions of fat are:

•  To provide structure, texture and taste including creaminess.
•  To act as a carrier of flavour and vitamins
•  To serve as a source of energy and essential fatty acids.

The physical properties of spreads, namely, spredability, firmness, plasticity and thixotropy are mainly determined by the ratio of liquid to solid fat content. For low-fat dairy spreads, sources of milk fat include cream, butter and butteroil of ghee.A somewhat better product in terms of body and texture characteristics can be obtained with the use of cream in place of butter for spread manufacture. To obtain 40 % fat in the finished product, cream having 65-67 % fat content is necessary.Since cream contributes substantial amount of milk solids-not-fat (MSNF), quantity of additional protein/MSMF required is generally less with cream based spreads.Cultured cream imparts butter flavour and desirable spredability to the spread. It also imparts a softer texture to the spread. Use of butter gives less oiling off and a pleasing, characteristic butter flavour as compared to butteroil. It gives firmer body than cream. Equal quantity of butter and 40% fat pasteurized cream can be used as a source of milk fat in a 60% dairy spread. Use of butteroil simplifies compositional control because the gross composition of butteroil is reasonably constant,being almost 100 % fat. The use of butteroil is recommended in case of unavailability of butter, as it offers ease in tempering and re-pasteurization just prior to use in spread-making, which help in improving the bacteriological quality of the product.

However, butteroil has a tendency to yield product with more oiling off and less tight structure than that with butter. Spreads with a stable emulsion can be prepared using 35 to 40% fat. Low-fat dairy spread with milk fat content below 35% may have a weak body and inferior spredability in addition to poor flavour.

Fats sources other than milk fat include vegetable oils such as corn, safflower,sunflower, soybean, and groundnut oils. These oils used in combination or singly, are usually subjected to partial hydrogenation prior to use. Health considerations favour use of monounsaturated (oleic-acid) fats/ oils such as groundnut (or, peanut), sesame and canola (rapeseed) oils. Olive oil would be the most desirable but it is rather expensive. At present most spreads available in the North American and European markets contain 17-33% saturated fat, 22-50% mono-unsaturated fat and 26-45% polyunsaturated fat.

The fat phase of non-dairy spreads comprises unhydrogenated and partially hydrogenated oils. However, hydrogenated fat is regarded as an unhealthy fat because of its ‘trans’ fatty acids (e.g., elaidic acid) content. In view of this‘interesterified’ fat with the desired plasticity but without trans fatty acids has been found more desirable.Another health-related feature of newer spreads is fat containing omega-3 fatty acids which is found in appreciable concentrations (6-10%) in fish oils, walnut oil,mustard (or, rapeseed) oil and soybean oil. Phytosterol (plant sterols) added as an additive and/ or in the form of oils containing the same (e.g. rice-bran oil) is also considered to make low-fat spreads more heart healthy.

 

ii. Protein Products

Milk proteins are generally added to dairy and non-dairy spreads for their organoleptic,functional and nutritional properties. They impart a creamy taste contribute viscosity and water holding capacity to the aqueous phase, thereby improving emulsion stability during processing and storage. The main sources of proteins are skim milk,buttermilk, caseinate and whey solids. Use of ripened cheese in fat spreads would not only provide easily digestible protein but also help in imparting cheese flavour to the product. Skim milk and butter milk are used as such or in a concentrated or dried form.

Condensed skim milk produces spread with a firm body and least wheying off.Skim milk powder (SMP) also yields a product with good body and water retention properties. Spread prepared using calcium-reduced SMP has a very strong water binding characteristic. Use of sodium caseinate imparts a soft body to the spread without causing wheying off. The caseinate can be used for both moisture retention and emulsion stability. However, use of excess (e.g. 1.5%) sodium caseinate imparts a ‘gluey’ taste to the product.

Milk protein concentrate derived from skim milk or buttermilk by ultrafiltration (UF) can be used to ensure formation of desired structure and binding of water. Buttermilk protein together with the butteroil gives a butter-like flavour to the product. In comparison to SMP, butter milk powder is superior in terms of both taste and emulsifying ability.Use of whey solids in spreads may cause a problem of lactose crystal formation.Cheddar cheese whey powder promotes softness in the product and excludes free whey during thawing. Use of whey protein concentrate (WPC) prepared by UF also improves the body of the product with the least wheying off.Among vegetable protein products, soy protein isolates have been frequently used in manufacture of spreads because of high water holding capacity and high protein quality. It can be also used in the form of protein-lipid concentrate so as to utilize the polyunsaturated soy oils as well.The proportion of fat and MSNF influences the quality of a spread. An increase in fat/SNF ratio results in increased wheying off and decreased body strength. Milk protein in the form of MSNF can be used at the level of 5-15 %.

 

iii. Emulsifiers and Emulsifying Salts

In order to get a stable emulsion, various emulsifiers are also employed in spread-making. Emulsifiers yield a softer and more easily spreadable product with a stable emulsion. It improves the mouth-feel of the product. Various emulsifiers are used in spreads, e.g., monoglycerides (MG) of saturated and unsaturated fatty acids, egg yolk solids, lecithin, combination of lecithin and MG, hydrophobic compounds such as methylated silicon oxide, etc. The level of emulsifiers in spreads may vary from 0.1 to 0.6 %.

Chelating or sequestering agents (i.e. chemicals that bind calcium and magnesium),also known as ‘emulsifying salts’ include tri-sodium citrate, di-sodium phosphate,etc. These are used either singly or in combination usually at the rate of 1 to 4 % to improve the emulsification by proteins, and enhance the texture of spread,especially of the O/W type.

 

iv. Stabilizers

A low-fat spread with a moisture content of 30-50% has a tendency to wheying off (or, syneresis), and exhibits poor body and consistency in absence of suitable stabilizers. The high water-holding ability of stabilizers plays an important role in improving body and texture of products. They yield an emulsion that gives good melt-down in the mouth and consequently, rapid flavour release with a satisfying cooling effect. Various stabilizers such as gelatin, carboxymethylcellulose(CMC), starch, modified starch, sodium alginate, xanthan gum, carrageenan,pectin, gum acacia, etc. can be used individually or in combination at the rate of 0.1 to 0.5 %.

 

v. Plasticizers

Plasticizers like glycerol, sorbitol, glycol, etc may be used in spreadable products to improve their pliability or plasticity. They also depress the water activity of the aqueous phase. This may help in extending the shelf life of the product. Addition of glycerol and sorbitol at the rate of 0.5-1.0 % in low fat spreads improves the mouth-feel and spreadability.

 

vi. Acidulants

Spreads, in general, have low a storage stability owing to their high moisture content. Acidification of the product helps in extending the shelf life as well as enhancing the flavour. The pH may be reduced to 4.8 to 6.0 with the use of different acidulants such as citric acid, lactic acid, ascorbic acid, and phosphoric acid. Addition of lactic acid improves the body and imparts a slightly tart flavour to the spread. Very low pH would, however, cause more wheying off. Best body and least syneresis can be obtained with pH from 5.7 to 5.9 in most spreads.

 

vii. Colouring matter

In order to make the spread visually attractive, two types of colour, namely anatto and b-carotene are added. O/W -type spreads require water-soluble annatto colour(anatto cheese colour), whereas W/O spreads require oil soluble anatto colour(anatto butter colour). Use of b-carotene enhances not only the nutritive value but also the oxidative stability of the product. Anatto colour can be used in low-fat spreads at the rate of up to 0.3%. Butter annatto is usually added to the fatty phase.

 

viii. Flavouring Agents

A spread without added flavouring often tastes rather bland. Hence, it is necessary that external flavourings are added. Use of butter starter distillate, synthetic butter flavour, diacetyl, phenols, ä-lactones, etc. have generally been found to effectively simulate the desired butter flavour. Diacetyl (0.5 – 2 ppm) is the most frequently used flavouring. A suitable dairy culture (starter) can be used @ 1% in spreads to give a mild, ripened flavour, acceptable to most people. Cultured buttermilk solids have an advantage of imparting a diacetyl aroma to the spread.

 

ix. Common salt

Sodium chloride or table salt is usually added to spreads. It provides taste and palatability to the spread and also retards the growth of bacteria, thereby acting as a preservative. Generally, the salt content in low-fat spreads varies from 0.25 to 2 %. Cheese-flavoured spreads involve the use of cheese flavour concentrate,aged Cheddar cheese, or blue cheese. Addition of melted cheese as a protein ingredient as well as flavouring material can yield a low fat spread with high overall quality. Other flavourings like herbs, garlic, chocolate, vanilla, honey, nuts, etc. can be used to enhance the acceptability of low-fat spreads.

 

x. Preservatives

In general, high-moisture foods such as spreads have low stability against microbial spoilage. In order to inhibit the growth of spoilage organisms including yeasts and molds, various preservatives may be added besides following an appropriate heat treatment. Sorbic acid and its salts, nisin, propionates, benzoic acid, sodium benzoate, etc. can be added upto 0.1 % to extend the shelf-life of spreads.

 

xi. Other additives

Other additives like anti-oxidants, vitamins, sweeteners, etc. are sometimes incorporated into low-fat spreads. Use of certain antioxidants like nordihydroguaratic acid (NDGA), hydrophobic metal oxide or methylated silicon dioxide, and alcohol etc. have been suggested to prevent oxidation of fat during storage. Spreads are often fortified with vitamins to enhance their nutritional value. These vitamins include ascorbic acid, vitamin A (3000 IU / 100 g) and Vitamin D (300 IU / 100g).