Analysing conjoint data with OLS and PLS regression: a case study with wine

BACKGROUND

This paper presents a case study with wine where two statistical methods for the analysis of rating-based conjoint analysis data were applied. Traditionally, ordinary least squares (OLS) regression is used to estimate the relative importance of the experimental factors and the part-worth utilities of factor levels. Partial least squares (PLS) regression, which is a popular tool in sensory and consumer science, can also be used for the analysis of interval-level conjoint data.

RESULTS

Using conjoint analysis, purchase intentions for Californian red and white wine were obtained from a convenience sample of young US adults (n ≈ 250). OLS and PLS regression uncovered the same systematic patterns in the data: negative utility associated with more expensive wine, and positive utility associated with famous wine regions. While OLS regression provided more accessible top-line results, an advantage of PLS regression was the graphical format of results. This provided easy insight to individual differences in the importance attached to the factors driving purchase intention.

CONCLUSION

OLS and PLS regression can complement each other in the analysis of interval-level conjoint data. Dual analysis can help to ensure that the right insights are drawn from the study and communicated to internal/external clients. It may also facilitate communication within project teams.

A Mendelian trait for olfactory sensitivity affects odor experience and food selection

Humans vary in acuity to many odors [1-4], with variation within olfactory receptor (OR) genes contributing to these differences [5-9]. How such variation also affects odor experience and food selection remains uncertain [10], given that such effects occur for taste [11-15]. Here we investigate β-ionone, which shows extreme sensitivity differences [4, 16, 17]. β-ionone is a key aroma in foods and beverages [18-21] and is added to products in order to give a pleasant floral note [22, 23]. Genome-wide and in vitro assays demonstrate rs6591536 as the causal variant for β-ionone odor sensitivity. rs6591536 encodes a N183D substitution in the second extracellular loop of OR5A1 and explains >96% of the observed phenotypic variation, resembling a monogenic Mendelian trait. Individuals carrying genotypes for β-ionone sensitivity can more easily differentiate between food and beverage stimuli with and without added β-ionone. Sensitive individuals typically describe β-ionone in foods and beverages as "fragrant" and "floral," whereas less-sensitive individuals describe these stimuli differently. rs6591536 genotype also influences emotional associations and explains differences in food and product choices. These studies demonstrate that an OR variant that influences olfactory sensitivity can affect how people experience and respond to foods, beverages, and other products.

Analysis of genetically modified red-fleshed apples reveals effects on growth and consumer attributes

Consumers of whole foods, such as fruits, demand consistent high quality and seek varieties with enhanced health properties, convenience or novel taste. We have raised the polyphenolic content of apple by genetic engineering of the anthocyanin pathway using the apple transcription factor MYB10. These apples have very high concentrations of foliar, flower and fruit anthocyanins, especially in the fruit peel. Independent lines were examined for impacts on tree growth, photosynthesis and fruit characteristics. Fruit were analysed for changes in metabolite and transcript levels. Fruit were also used in taste trials to study the consumer perception of such a novel apple. No negative taste attributes were associated with the elevated anthocyanins. Modification with this one gene provides near isogenic material and allows us to examine the effects on an established cultivar, with a view to enhancing consumer appeal independently of other fruit qualities.

Genetic variation in the odorant receptor OR2J3 is associated with the ability to detect the "grassy" smelling odor, cis-3-hexen-1-ol

The ability to detect many odors varies among individuals; however, the contribution of genotype to this variation has been assessed for relatively few compounds. We have identified a genetic basis for the ability to detect the flavor compound cis-3-hexen-1-ol. This compound is typically described as "green grassy" or the smell of "cut grass," with variation in the ability to detect it linked to single nucleotide polymorphisms (SNPs) in a region on human chromosome 6 containing 25 odorant receptor genes. We have sequenced the coding regions of all 25 receptors across an ethnically mixed population of 52 individuals and identified 147 sequence variants. We tested these for association with cis-3-hexen-1-ol detection thresholds and found 3 strongly associated SNPs, including one found in a functional odorant receptor (rs28757581 in OR2J3). In vitro assays of 13 odorant receptors from the region identified 3 receptors that could respond to cis-3-hexen-1-ol, including OR2J3. This gene contained 5 predicted haplotypes across the 52 individuals. We tested all 5 haplotypes in vitro and several amino acid substitutions on their own, such as rs28757581 (T113A). Two amino acid substitutions, T113A and R226Q, impaired the ability of OR2J3 to respond to cis-3-hexen-1-ol, and together these two substitutions effectively abolished the response to the compound. The haplotype of OR2J3 containing both T113A and R226Q explains 26.4% of the variation in cis-3-hexen-1-ol detection in our study cohort. Further research is required to examine whether OR2J3 haplotypes explain variation in perceived flavor experience and the consumption of foods containing cis-3-hexen-1-ol.

A construct analysis of meal convenience applied to military foods

The present research investigates the concept of food convenience within the institutional framework of military feeding. The approach views food-related convenience in terms of two broad dimensions: "type of convenience" and "timing of convenience." A discrete choice experiment was conducted with US military personnel (n=179) regarding their perceptions of the (in)convenience associated with the use and consumption of low-preparation, all-in-one, military meals (MREs-meals, ready-to-eat). The obtained data strongly suggest that perceived (in)convenience, time and effort are separate constructs. A food provisioning process perspective was captured in the "timing of convenience" dimension, and the contribution of different stages in the consumption process to the perceived convenience of the meal situation was empirically demonstrated. The latter result has important implications for the study of food convenience outside this specific population and context. As opposed to the product perspective that is currently predominant in the literature, it demonstrates the necessity of adopting a meal perspective in analysing food-related convenience.