Where to do your sensory test?

We know context is important. A whole fish you just caught and cooked, eaten by the ocean, would be far preferable than eating the meal on public transport. This brings into question the relevance or validity of hedonic testing in controlled lab environments, where your actual experience is far from realistic (although highly controlled).

Researchers from Wageningen University in the Netherlands investigated liking of a meal in a laboratory setting, in a re-created airplane environment, and during an actual flight. They provided two meal types from which to choose – pasta Bolognese and chicken curry with rice. Each meal had two variations, which were authentic as they actually came from two different airlines! The 242 participants were asked which meal they would like and were randomly allocated one of the meal variants. Consistent with prior research, all of the meals were acceptable but not overly liked. The meals were less liked in the laboratory setting than in the simulated flight or actual flight, which was also consistent with previous research showing that context is important. The magnitude of effect, however, was very small – differences between lab setting and plane were 4-6 units on a 100-point scale.

The controlled environment of a lab is ideal for maximising tested food’s potential but, as the field of sensory and consumer testing evolves, the application of mobile technology is a significant boost to research and development – mobile technology will vastly improve our ability to test liking in natural settings.

 

Bitter Hazelnuts

Have you ever noticed a bitter, off-taste in hazelnuts? Researchers in Germany have identified the chemical compound responsible for this taste, which occurs sporadically in hazelnut crops during storage time as well as in hazelnuts affected by the bug Cimiciato (which induces tissue necrosis in the nuts, decreasing flavour quality).

The researchers utilised comparative taste-guided fractionation. Freeze-dried hazelnut samples were extracted in different solvents to provide fraction I (pentane-soluble), fraction II (acetate-extractable), and fraction III (water-soluble), as well as fraction V (residual hazelnut material). Seventeen sensory panellists (who were trained to evaluate aqueous reference solutions once a week for ≥2 years) evaluated fractions I-IV as diluted to normal concentrations in water for bitterness, astringency and sweetness. Fraction IV was found to have no taste activity, and fraction II was intensely bitter with a rating of 4.0/5.

Taste Dilution Analysis (TDA) was then performed by the panel on 12 Medium Pressure LC (MPLC) subfractions of fraction II. The Taste Dilution (TD) factor for bitterness was highest for subfraction II-8. Further analysis using multiple analytical techniques identified the bitter taste compound as asadanin, a cyclic diarylheptanoid.

Once identified, the researchers determined the Human Taste Recognition Threshold using a two- alternative forced-choice test, to reveal an average threshold value of 13.0 µmol/L for asadanin (average concentration at which bitterness of asadanin is detectable).

The sensory panel then analysed three variations of hazelnut: Cimiciato-infected Ordu, Ordu from 2013, and Akçakoca from 2014. Quantitation of asadanin was found to correlate with bitterness ratings for the three hazelnut varieties, and Cimiciato-infected Ordu had the highest bitterness rating (4.0/5) and concentration of asadanin (44.8 µmol/kg). Future research aims to understand the mechanisms of asadanin formation.

 

Virtual Reality

Virtual reality (VR) is gaining great momentum in consumer research. The technology can be as simple as a mobile phone in a carton box, and as complicated as immersing all senses into the VR space. VR enables researchers to quickly manipulate and control the visual environment in which consumers behave, for example a grocery store.

Traditionally consumer food choice behaviour has been investigated in real life or with photos of products in a confined lab setting. Several researchers rightfully pointed out that these lab experiments have trouble measuring consumers’ responses to the physical position of products on a shelf. Also, because of social awareness (eg. I am in a lab, I am being watched), lack of distraction (eg. you see a photo of a product, not the clutter surrounding the product) consumers behave differently than in real life.

In theory, a VR shopping experience can overcome some of these issues because it supposedly draws people into more of a real shopping experience, causing them to behave more naturally. However, virtual reality is still artificial.

To investigate how well a real shopping experience relates to a virtual reality and a traditional lab experience (eg. looking at photos of products), van Herpen and colleagues compared the three methods in a series of clever experiments. In the real shopping experience, participants were asked to shop for specific product categories – habitual purchases (eg. milk), tactile and sensory purchases (eg. fruit and vegetables that consumer often feel, squeeze and smell before buying) and impulse purchases (eg. biscuits).

In the virtual reality condition, participants looked at three screens set up so that participants had a 180-degree view of a shopping aisle and could walk through the aisle and zoom in on products as they pleased. In the traditional experiment, participants looked at photos of aisles and products. It was found that for milk (habitual purchases), the virtual reality experiment was better able to predict the number of milk products bought in a real store. For the other product categories, the virtual reality and traditional experiments were less predictive of what happens in real life – consumers bought more products and spent more money in the lab conditions than in real life. The benefit of virtual reality over the traditional photo experiment is that it is sensitive to where products are placed on shelf, just like real in real life. A real shopping experience involves all our senses as well as the real effort of bending over or stretching when a product is placed away from eye height. Each sense and effort is likely to contribute to the real shopping experience and should ideally be part of a virtual experience. This is an exciting area of research that will evolve quickly.

 

The link between astringency and bitter taste phenotype

Astringency causes drying, puckering and tightening of the oral surface and muscles surrounding the mouth. Tannins elicit astringency and are found in grapes, berries, apples, tea, chocolate and beer. Taste sensitivity to the bitter taste marker, 6-n-propylthiouracil (PROP), has been linked to differences in food preferences and eating behaviours. For instance, previous research has shown that those who are highly sensitive to PROP express a greater dislike and more frequent rejection of astringent foods compared to those less sensitive to PROP. A recent investigation aimed to determine the relationship between PROP sensitivity and astringency perception. Seventy-nine subjects rated astringency intensity and liking of a cranberry juice cocktail drink (CJC, with added sugar) with and without added tannic acid (0, 1.5 or 2.0 g/L). Saliva for protein analysis was collected at baseline and after stimulation with a tannic acid solution and a cranberry juice drink (CJ, without added sugar).

Findings indicated a gender-specific role for PROP sensitivity and perception of astringency. For instance, CJC (containing 1.5 g/L tannic acid) was found to be less astringent and liked more by male subjects less sensitive to PROP compared with males more sensitive to PROP. The same finding was not found in females. For all subjects, the salivary proteins – acid and basic proline-rich proteins – reduced after exposure to the tannic acid solution, but the same proteins together with cystatins increased after CJ exposure only in those sensitive to PROP. Acid and basic proline-rich proteins and cystatins have been linked to protective effects in the oral cavity. This study provides a base for further investigation into the role of cranberry products in oral health, particularly for those with differing sensitivities to PROP.