Liking of health-functional foods containing lupin kernel fibre following repeated consumption in a dietary intervention setting

Abstract

Liking of a particular food after repeated consumption may be reduced, limiting the effectiveness of health-functional foods requiring on-going consumption to deliver their benefits. This study examined the effect of repeated consumption of foods containing the novel ingredient, Australian sweet lupin (Lupinus angustifolius) kernel fibre (LKFibre) on sensory acceptability in the dietary intervention setting. In a single-blind randomised crossover 4-week intervention, participants consumed both control and equivalent LKFibre-containing products daily on separate interventions separated by a 4-week period on habitual diet. Seven products: muesli, bread, muffin, chocolate brownie, chocolate milk drink, pasta and instant mashed potato were assessed twice (days 4 and 18 of intervention), by 38 participants for appearance, texture, flavour and general acceptability using a structured graphic hedonic scale. Overall the results showed there was no reduction (P = 0.594) in general acceptability of LKFibre foods after repeated consumption, suggesting potential for long-term consumption. The control food products were however generally preferred (P < 0.001) over the LKFibre foods; the mean difference for general acceptability between being <6% (0.82 cm) of the 15 cm hedonic scale used, suggesting LKF addition did not severely affect product palatability.

Introduction

Functional foods is one of the most rapidly expanding sectors of the food industry predicted to have a global market value of US$90.5 billion by 2013 (Just-Food, 2008). Functional foods can only achieve their health-enhancing effects if they are regularly consumed as part of the diet. Palatability of these foods is therefore extremely important in determining whether they will be repeatedly consumed and can thus assist in the long-term prevention of disease (Drewnowski & Gomez-Carneros, 2000). Cardello and Schutz (2003) highlighted the importance to consumers of palatability of foods even when potential health benefits are apparent. Therefore the incorporation of dietary fibre ingredients into food products is a balance between product acceptability and the dose required for disease risk reduction.

Sensory-specific satiety is relevant to understanding the desire for repeated consumption of functional foods since it describes the decrease in both short-term “liking” and “wanting” of a food after its consumption compared to that for unconsumed food (Havermans, Janssen, Giesen, Roefs, & Jansen, 2009). In addition, this phenomenon has been suggested to influence consumers’ likelihood of repeat purchase of a food product (Manthey & Vickers, 1996). However the extent of short-term reduction in the acceptability of a food immediately after consumption may not reflect its “desire-to-eat” after repeated long-term consumption (Zandstra, deGraaf, Mela, & Van Straveren, 2000). Studies in both military personnel and refugees in care have provided evidence that lack of variety of foods (monotony) can lead to reduced acceptability of these foods (Kramer et al., 2001, Meiselman et al., 2000, Meiselman and Schutz, 2003, Rolls and de Waal, 1985). Even highly palatable food products such as those based on chocolate have been shown to decrease in perceived pleasantness after repeated consumption (Havermans et al., 2009, Hetherington et al., 2002). Importantly however, it has been reported that lesser preferred foods as judged immediately after initial consumption can, after repeated consumption over extended time, become relatively more desirable (Zandstra, deGraaf, Mela, et al., 2000). Since it may only represent a momentary or immediate perception, the relevance of initial hedonic judgements, as used commonly by food industry, to long-term preference and willingness for repeated consumption is questionable (Lévy & Köster, 1999).

It is generally recognised that dietary fibre intake in most Western countries is less than adequate for prevention of major non-communicable diseases (Marlett, McBurney, & Slavin, 2002). Dietary fibre fortification of food products began in the 1970s, with the fortification of bread products for the weight loss market (Gelroth & Ranhotra, 2001). Food manufacturers have since used a wide variety of dietary fibre ingredients for both technologically and physiologically functional purposes to improve textural properties and provide potential health benefits. Dietary fibres can be used in a range of food matrices such as bakery products, breakfast cereals, pasta and noodles, beverages, meat products and dairy products. There is currently a paucity of data investigating the effect on acceptability of repeated consumption of dietary fibre-enriched food products in the context of the whole diet. Manthey and Vickers (1996), however have suggested that there is no sensory-specific satiety associated with consumption of food products containing additional dietary fibre.

Lupin kernel fibre (LKFibre) is a novel legume component with potential as a functional food ingredient demonstrating beneficial effects in human clinical studies on cholesterol (Hall, Johnson, Baxter, & Ball, 2005), insulin response (Johnson, McQuillan, Sin, & Ball, 2003), satiety response and post-meal food intake (Archer, Johnson, Devereux, & Baxter, 2004), bowel function and faecal chemistry (Johnson, Chua, Hall, & Baxter, 2006) and colonic microfloral balance (Smith et al., 2006). LKFibre has demonstrated acceptable palatability in single sample conventional sensory evaluation trials when incorporated into a range of food products, though lower palatability of the LKFibre variant of some food types compared to the control was reported (Clark & Johnson, 2002). Similar acceptable palatability ratings were also found in single-meal feeding trials (Archer et al., 2004, Johnson et al., 2003). However the effect of repeated consumption in a dietary setting on the acceptability of LKF containing foods, particularly in light of previous finding that initially less desired foods can become relatively more desired after repeated consumption (Zandstra, deGraaf, Mela, et al., 2000), was unknown and was therefore the aim of this study.