Combined sensory optimization of a prebiotic cereal product using multicomponent mixture experiments

Abstract

An experimental design for mixtures was used to develop tasty cereal bars with prebiotic properties. Inulin (I), oligofructose (OF) and gum acacia (GA) were the prebiotic ingredients added (13.5% w/w) to cereal and fruits. The bars were analyzed by QDA (quantitative descriptive analysis) and the best formulations were determined in accordance with a preference test. GA was responsible for effects on dryness appearance of cereals flakes, hardness and chewiness while OF enhanced the brightness and crunchiness. The optimized formulations (50% I + 50% OF + 0% GA and 8.46% I + 66.16% OF + 25.38% GA) showed that blends of fibres imparted, to the bars, better textural characteristics than did each fibre alone. Syrup viscosity (greatly influenced by GA concentration) had a negative correlation (r = −0.904) with the preference score. The selected formulations aimed at reduction of 18–20% caloric value while providing an average increase of 200% in total fibre.

Introduction

Today, the industrialized countries are facing, among others, three major challenges:

• to control the cost of health care;

• to offer to their aging population a real opportunity to live, not only longer, but also better;

• to provide to more and more “busy” consumers, a choice of healthy processed or ready-to-eat foods (Roberfroid, 1999).

The development of functional foods is a unique opportunity to contribute to the improvement of the quality of food and to consumer health and well-being (Hasler, 1998, Milner, 1999).

Everybody agrees that food must taste good to gain acceptance. The other characteristics that consumers look for are: the convenience, nutrition and price of the food (Boustani and Mitchell, 1990, Bower and Whitten, 2000, Izzo and Niness, 2001, Katz, 1999). When formulating any successful product, a food company must perform consumer tests to determine which products are liked by the consumer (Yackinous, Wee, & Guinard, 1999). Consumer testing usually follows discrimination and descriptive tests and is a necessary and valuable component of every sensory programme (Stone & Sidel, 1993). These tests indicate which sensory characteristics and levels of these characteristics a product should exhibit in order to be successful in the market place.

The development of a product is essentially a problem of optimization. In the search for the best formulation, the main objective is to determine the optimum levels of the components or key ingredients. The ingredients are the independent variables or factors and the dependent variable or response is the objective to be optimized (maximized or minimized) (Castro, Silva, Tirapegui, Borsato, & Bona, 2003). Mixture experimental designs are suitable for food products that require a composition or a blend of key ingredients, since proportions of the ingredients in the mixture, and their levels, are dependent on each other, and the sum of all components is always one or 100% (Hare, 1974).

Energetic and cereal bars have proliferated recently, and Americans spend a little over half of their food money on food prepared for eating without much – if any – further cooking (Katz, 1999). Busy life styles and the increasing demand from consumers for meals and snacks that are quick sources of good nutrition have prompted the food industry to develop foods like nutrition bars that combine convenience and nutrition (Izzo & Niness, 2001). The cereal bars have gained an acceptance in the consumer’s eyes as being “better for you” and good in nutritional terms, from the contribution of a amount of dietary fibre. The popularity of these products reflects nutritional guidelines recommending increased dietary fibre intake since low fibre consumption has been implicated as a risk factor in many diseases (Murphy, 2001). Insoluble fibre ingredients, such as bran, have traditionally been used in products such as cereal bars, breads, pasta and breakfast cereals, but the palatability of these has limited the level that can be incorporated into different systems. Soluble fibre ingredients are currently of greater interest in the formulation of “healthy” foods because they are more palatable. In addition, some can be used in food systems to thicken, add viscosity or gel (Dreher, 1999).

According to the definition of the American Association of Cereal Chemists (AACC, 2001), dietary fibres promote beneficial physiological effects, including laxation, and/or blood cholesterol attenuation, and/or blood glucose attenuation. Aside from its laxative effects, possibly the most dynamic function of dietary fibre is its fermentation, which causes a myriad of biochemical, physiological, and microbiological changes in the large intestine. The potential impact of fermentation in the intestine is helping us better understand that the entire intestine can contribute to better health if properly nourished. This belief and a growing understanding of dietary fibre fermentation helped coin the term “prebiotic”. Prebiotics are food ingredients that selectively stimulate the growth and activity of bifidobacteria and lactic acid bacteria in the human intestine (Gibson, 1999, Gordon, 2002).

The most important effect of prebiotic carbohydrates is to strengthen the body’s resistance to invading pathogens and, thereby, prevent episodes of diarrhoea (Cummings & Macfarlane, 2002). Research has shown that a balanced intestinal flora can provide improved regularity, stimulation of immune factors, production of digestive enzimes, and assistance in controlling the formation of free radicals (Gibson and Williams, 1999, Kummel and Brokx, 2001).

The prebiotic effects of inulin, oligofructose and gum acacia have been confirmed in previous laboratory and human trials (Cherbut, 2000, Kolida et al., 2002).

Inulin, oligofructose and gum acacia are soluble fibres well suited for use in diabetic or low-calorie foods. The ingredients also offer a variety of technological functional properties: water retention, enhanced viscosity for improving binding and texture, stability at different temperature levels, and a stable pH (Pszczola, 1999).

The aim of this study was to develop tasty cereal bars with prebiotic functional properties using three sources of fibres – inulin (I), oligofructose (OF) and gum acacia (GA), looking for an optimization of the texture and taste.