In the late 1970s margarine manufacturers started to develop low-energy or ‘light’ spreads. The challenge was to develop a product with less than half the fat content, but with the same flavour, texture and spreading characteristics as the traditional product. Margarine is a water-in-oil emulsion that consists of 80% fat and 20% water (see Fig. 3). The fat level (80%) has a historical background; butter also contains 80% fat. The microstructure of margarine consists of small water droplets in liquid oil stabilised by a structure of solid fat crystals. The structure of low-fat margarine is comparable with that of full-fat margarine; however, four times the amount of water must be incorporated into the fat matrix. To achieve this level of incorporation technologists required a way of stabilising or structuring the water. Water can be structured by trapping it within a matrix of long molecular chains, as for example in jam or marmalade. Pectin, alginate and (modified) starches are commonly used to structure the water in low-fat spreads. An important characteristic of the structured aqueous phase is that the viscosity decreases at mouth temperature, to mimic the melting behaviour of high-fat spreads.
The success or failure of ‘light’ products is determined by their taste; the ‘light’ product should taste as good as the ordinary product. Consumers expect the product to have the same quality attributes as their usual product; in the case of low-fat spreads flavour, product structure and water leakage are the key issues. The flavour associated with margarine is determined by added flavour compounds and salt. Traditionally, the flavour compounds used in margarine are partly soluble in fat and partly in water. There is an equilibrium between the level of flavour compounds in the product and that in the headspace (i.e. the air above the product in the packaging) of the product. These volatile components are responsible for the aroma of the product. As in low-fat spreads the proportion of water and oil is changed, and a new generation of flavour cocktails had to be developed for these products.
As rates of obesity in Europe have been steadily increasing over the past 50 years, resulting in more of the population with elevated blood cholesterol concentrations who are also overweight (World Health Organization, 2003), low-fat high-PUFA spreads are even more relevant at present. It is advised that weight loss is best achieved by reducing dietary energy intake and increasing physical activity (National Institutes of Health, 1998). However, weight loss per se appears to have little effect on TC and LDL-cholesterol and results in only minor improvements in serum TG and HDL-cholesterol concentrations (Yu-Poth et al. 1999). To improve weight management and blood lipid profiles the best results are achieved by the use of energy-restricted diets that are low in SFA and trans-fatty acids (TFA) in conjunction with increased physical activity (Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, 2001).
As a result of the technological achievements in the area of low-energy spreads, low-fat versions of nearly all Unilever margarine brands became available in the 1970s. As low-fat spreads contain less fat, they also generally contain a lower SFA level compared with the high-fat versions. This reduction in SFA is possible because there is less liquid oil to structure and part of the product structure is now provided by the structured water phase. ‘Light’ versions of high-PUFA spreads, being low in SFA, perfectly fit with current recommendations for blood cholesterol management.
Answers to all your Biology Questions
