Evaluation of the sensory characteristics of strawberry cultivars throughout the harvest season using projective mapping

Storage of halved strawberry fruits affects aroma, phytochemical content and gene expression, and is affected by pre-harvest factors

Introduction

Strawberry fruit are highly valued for their aroma which develops during ripening. However, they have a short shelf-life. Low temperature storage is routinely used to extend shelf-life for transport and storage in the supply chain, however cold storage can also affect fruit aroma. Some fruit continue to ripen during chilled storage; however, strawberries are a non-climacteric fruit and hence ripening postharvest is limited. Although most strawberry fruit is sold whole, halved fruit is also used in ready to eat fresh fruit salads which are of increasing consumer demand and pose additional challenges to fresh fruit storage.

Methods

To better understand the effects of cold storage, volatilomic and transcriptomic analyses were applied to halved Fragaria x ananassa cv. Elsanta fruit stored at 4 or 8°C for up to 12 days over two growing seasons.

Results and discussion

The volatile organic compound (VOC) profile differed between 4 or 8°C on most days of storage. Major differences were detected between the two different years of harvest indicating that aroma change at harvest and during storage is highly dependent on environmental factors during growth. The major component of the aroma profile in both years was esters. Over 3000 genes changed in expression over 5 days of storage at 8°C in transcriptome analysis. Overall, phenylpropanoid metabolism, which may also affect VOCs, and starch metabolism were the most significantly affected pathways. Genes involved in autophagy were also differentially expressed. Expression of genes from 43 different transcription factor (TF) families changed in expression: mostly they were down-regulated but NAC and WRKY family genes were mainly up-regulated. Given the high ester representation amongst VOCs, the down-regulation of an alcohol acyl transferase (AAT) during storage is significant. A total of 113 differentially expressed genes were co-regulated with the AAT gene, including seven TFs. These may be potential AAT regulators.

Modelling strawberry quality in a longitudinal study under the marketing concept of branding

Background

Marketing strategies, such as branding, redefine how consumers perceive quality and create new requirements related to season length and quality homogeneity, among others. For short-day (SD) strawberry cultivar brands, the commercial season is short due to a dependency on temperature and photoperiod. A plausible strategy to extend the commercialization period is to use different varieties within a single brand; however, this has led to inconsistent quality in other fruit crops. A form of quality assessment to evaluate the impact of a multi-varietal brand on sensory quality is a critical longitudinal study with several sources of variability, such as the inherent variation among assessors and fruit replicates that can affect the reliability of the results. Therefore, this study aimed to develop a methodology to assess the sensorial and physicochemical quality of strawberry brands in two contexts: a short-term season composed of two SD cultivars and a long-term season with one SD and one day-neutral (DN) cultivar.

Results

New statistical models are proposed in this study. An ANOVA mixed model with assessors and replicates as random terms and a multiple factor analysis highlighted a lack of homogeneity with regard to texture parameters and sourness, while partial least square models identified aroma and sweetness as the best quality indicators.

Conclusions

This work has successfully illustrated a methodology that is capable of handling critical aspects of longitudinal studies by using univariate models that account for different sources of variability and constrained multivariate models to relate parameters with overall liking. A long-term brand is a viable solution to valorise strawberries, as parameter heterogeneity did not affect overall quality.

Identifying Key Flavors in Strawberries Driving Liking via Internal and External Preference Mapping

Australian consumers desire the development of a more flavorsome Australian strawberry cultivar. To aid in the development of well-liked strawberries, the attributes driving liking need to be identified. The objective of this research is to apply Preference Mapping (PM) techniques to the descriptive profile of commercial and newly bred strawberry cultivars, together with consumer preference data to determine the flavors contributing to liking. A trained sensory panel (n = 12) used Quantitative Descriptive Analysis (QDA®) methodology to evaluate two appearance, seven aroma, five texture, 10 flavor and 10 aftertaste attributes of three commercial strawberry cultivars and six elite breeding lines grown in Victoria, Australia. Strawberry consumers (n = 150) assessed their liking of the same strawberry cultivars. QDA® significantly discriminated strawberries on 28 of the 34 sensory attributes. There were significant differences in hedonic ratings of strawberries (F(8,714) = 11.5, P = 0.0001), with Hierarchical Cluster Analysis (HCA) identifying three consumer clusters each displaying differing patterns of preference. Internal and external PM techniques were applied to the data to identify the attributes driving consumer acceptability. Sweet, berry, caramel, fruity and floral attributes were identified as most contributing to liking. Sour, citrus, green, astringent, firm and gritty attributes were conversely associated with a reduction in consumer liking. Elite Lines 2 and 6 have been identified as having the broadest appeal, satisfying between 60% and 70% of consumers in the population assessed, thus the introduction of these cultivars should satisfy the largest group of consumers in the Australian market.

PRACTICAL APPLICATION

The results of this research could be applied to breeding programs, to ensure newly bred cultivars express characteristics that were identified as well-liked amongst consumers. In addition, this research provides evidence for marketing strawberries by cultivar, to assist consumers in identifying those strawberries for which they have a preference.

Selection of promising sweet potato clones using projective mapping

BACKGROUND

Increasing demand for sweet potato in regions with temperate climates has triggered interest in the development of new cultivars. Breeding of this crop should consider sensory characteristics in order to meet consumers' expectations. This requires the application of simple and cost-effective methodologies that allow quality evaluation from a sensory perspective.

RESULTS

With the objective of identifying the key sensory characteristics of different sweet potato genotypes, two commercial cultivars and seven clones were evaluated during three consecutive years using projective mapping by an untrained consumer panel. This methodology allowed the discrimination of the genotypes, identifying similarities and differences among groups based on sensory terms selected by the assessors. Genotypes were differentiated in terms of texture and flavor characteristics (firmness, moisture, smoothness, creaminess, flavor intensity, sweetness and bitterness). Materials for future crossings were identified.

CONCLUSIONS

The evaluation of the sensory characteristics of sweet potato clones and cultivars using projective mapping is a quick, cost-effective and reliable tool for the selection of new advanced sweet potato clones with superior sensory characteristics compared to the reference cultivars INIA Arapey and Cuarí. © 2016 Society of Chemical Industry.