The effect of protease inhibitors derived from potato formulated in a minidrink on appetite, food intake and plasma cholecystokinin levels in humans.

BACKGROUND: Protease inhibitor 2 derived from potato (PI2) is claimed to reduce appetite and food intake, stimulate the satiety hormone cholecystokinin (CCK) and lower postprandial glucose peaks when taken before a meal. However, current literature is inconclusive with regard to its efficacy and mechanism. Furthermore, the potential effect of PI2 on appetite motivational ratings without an immediately following meal has not previously been reported. OBJECTIVE: To comprehensively test the effects of 30 mg PI2 in a minidrink on appetite ratings, subsequent food intake, and plasma CCK and glucose responses. DESIGN: Minidrinks with or without 30 mg PI2 were compared in three separate substudies (A, B and C), each using a two-way, placebo-controlled, balanced-order, cross-over design and 23 or 24 subjects (mean over groups: body mass index 25.0 kg m(-2), range 22.5-30.7 kg m(-2); age 41.3, range 18-62 years). The minidrink was given (A) 120 or (B) 30 min before an ad libitum lunch or (C) 30 min before a fixed lunch. Study parameters were self-reported satiety (substudies A and C), ad libitum meal intake (substudies A and B), and (in an n=12 subset) plasma CCK and blood glucose in all substudies. All results were analyzed using analysis of covariance. Protease-inhibitory activity of the PI2-containing minidrinks was assessed under simulated gut conditions. RESULTS: PI2 did not differ from control for any study parameters, in any substudy, despite confirmation of the inhibitory activity of PI2. CONCLUSIONS: In this study protease inhibition using PI2 in a minidrink at a dose of 30 mg, as commercially used, had no (functional) efficacy on a range of behavioral and physiological appetite and intake control measures.

Metabolically active functional food ingredients for weight control.

The scale of the obesity epidemic creates a pressing consumer need as well as an enormous business opportunity for successful development and marketing of food products with added benefits for weight control. A number of proposed functional food ingredients have been shown to act post-absorptively to influence substrate utilization or thermogenesis. Characteristics and supporting data on conjugated linoleic acid, diglycerides, medium-chain triglycerides, green tea, ephedrine, caffeine, capsaicin and calcium, are reviewed here, giving examples of how these could act to alter energy expenditure or appetite control. Consideration is also given to other factors, in addition to efficacy, which must be satisfied to get such ingredients into foods. We conclude that, for each of the safe, putatively metabolically active agents, there remain gaps in clinical evidence or knowledge of mechanisms, which need to be addressed in order to specify the dietary conditions and food product compositions where these ingredients could be of most benefit for weight control.

Perceptions of starchy food dishes: application of the Repertory Grid Method.

The Repertory Grid Method (RGM) was applied to obtain an understanding of the characteristics used by U.K. consumers in discriminating amongst different common starchy food dishes, including potatoes, rice and pasta. Twenty-nine subjects generated a large number of constructs, relating to perceived nutrition, health physiological effect, sensory, and use attributes of these products. Coupling of RGM with Generalized Procrustes Analysis produced detailed qualitative and quantitative information describing common and individual characteristics of particular dishes. The results indicate that starchy foods are in general seen as "filling", but specific products are clearly discriminated along two dimensions, predominantly relating to nutritional value ("healthy", "fatty", "fattening") and sensory/functional characteristics ("versatile", "bland", "boring", "a meal in itself"). Along with further analysis of the sensory descriptors, these results indicate the utility and efficiency of RGM for clarifying consumer views of broad food categories, while identifying the potential acceptability of particular starchy foods in fulfilling current dietary goals.

Sensory assessment of fat content: effect of emulsion and subject characteristics.

This work examines some of the fundamental stimulus properties contributing to the perception and discrimination of fat content in foods. In an initial experiment, oil-in-water (O/W) emulsions were prepared with 0, 5, 10, ..., 40, 45, and 50% sunflower oil (SUN) and homogenized at pressures of 100 and 300 bar. These were rated for "fat content" and "smoothness" on 9-point category scales. There were significant effects of fat concentration and processing pressure. Higher pressures, associated with a decreased fat particle size/number ratio, generated a slightly enhanced perception of fat content. In a second experiment, O/W emulsions were prepared with 0, 12, 24, 36, and 48% fat at 100 and 300 bar, from two oils differing in fat saturation: SUN and Hycoa 5 (HY5, a highly saturated commercial cocoa butter substitute). The results indicate significant main and interactive effects of fat type and concentration, but no significant effect of processing pressure were seen in this experiment. HY5 emulsions had a substantially greater measured viscosity and were judged higher in fat content than those prepared from SUN, particularly at higher fat levels. Analyses indicate a significant independent contribution of fat concentration to perceived fat content, beyond increased viscosity. There were no consistent main or interactive effects of subject age or body composition on judgments of fat content.