Fast Color Analysis of Red Raspberry Puree and Its Link to Antioxidant Levels

Jenn Hoskins
30th May, 2024

Fast Color Analysis of Red Raspberry Puree and Its Link to Antioxidant Levels

Visual assessment of 30 representative Rubus idaeus L. puree samples resulted in their unanimous categorization by panelists into distinct dark, medium, and light red groups, establishing a baseline for instrumental color analysis.

Image adapted from: Baldassi et al. / CC BY (Source)

Key Findings

  • Researchers at The University of British Columbia developed a high-throughput method to measure red raspberry puree color
  • The study analyzed 551 raspberry puree samples using a colorimeter and the Tomato Analyzer Color Test (TACT)
  • TACT measurements showed that darker raspberry colors corresponded with higher anthocyanin content
  • TACT with 96-well plates allows for efficient, large-scale color measurement in raspberry breeding programs
Red raspberry fruit color is a significant factor influencing consumer preference and a major focus for breeding programs globally. Traditional methods to screen for fruit color, such as determining anthocyanin content and using a colorimeter, are time-consuming, especially when dealing with large sample sizes. A recent study conducted by researchers at The University of British Columbia aimed to develop a high-throughput method for measuring red raspberry puree color and to test the correlations between color parameters and total anthocyanin content[1]. The study involved analyzing 551 raspberry puree samples. Color coordinates were collected using a colorimeter and the Tomato Analyzer Color Test (TACT) module on samples contained in Petri dishes and 96-well plates. Total anthocyanins were extracted from all samples to establish correlations between color parameters and anthocyanin content. Regression models for color parameters measured with the colorimeter and TACT using Petri dishes were significant, showing strong consistency for L (a measure of lightness) with an R² value of 0.94. Similarly, significant regressions were obtained for color parameters measured with TACT using both Petri dishes and 96-well plates, with R² values of 0.94 for L and b (a measure of yellowness), and 0.93 for a (a measure of redness). Among the colorimeter-measured parameters, L, a/b* (a ratio of redness to yellowness), and hue had significant, though weak, correlations with total anthocyanins. Conversely, TACT-measured parameters showed moderately strong correlations with total anthocyanins, indicating that darker colors corresponded with higher anthocyanin content. This study builds on earlier research demonstrating the importance of anthocyanins in determining raspberry color and their health benefits. For example, previous studies have shown that different raspberry varieties have varying levels of phenolics and flavonoids, which contribute to their antioxidant activities[2]. The Heritage raspberry variety, noted for its high phenolic and flavonoid content, exhibited the darkest juice color and the highest antioxidant activity[2]. This aligns with the current study's finding that darker raspberry puree colors, measured through TACT, are indicative of higher anthocyanin content. Moreover, the study's findings correlate with earlier research on wild and cultivated raspberry genotypes, which highlighted the variability in antioxidant capacities and phenolic content among different genotypes[3]. The ERZ5 genotype, for instance, demonstrated the highest antioxidant capacity and phenolic content, suggesting that specific genotypes could be targeted for breeding programs to enhance nutritional value[3]. The study also touches upon the genetic basis of raspberry color. Previous molecular analysis identified mutations in the anthocyanidin synthase (Ans) gene in yellow raspberries, leading to reduced anthocyanin content and lighter fruit color[4]. This genetic insight complements the current study's focus on anthocyanin content as a determinant of raspberry color. In conclusion, while the colorimeter and TACT methods are not fully interchangeable, TACT proved better at capturing color differences among raspberry genotypes. Although the correlations between TACT-measured color parameters and total anthocyanins were not strong enough to develop prediction models, using TACT with 96-well plates allows for high-throughput color measurement. This advancement could significantly streamline the screening process in raspberry breeding programs, making it more efficient to identify and select varieties with desirable color traits.

FruitsBiochemPlant Science

References

Main Study

1) High-throughput color determination of red raspberry puree and correlation of color parameters with total anthocyanins.

Published 30th May, 2024

https://doi.org/10.1186/s13007-024-01197-0

Related Studies

2) Antioxidant and antiproliferative activities of raspberries.

Journal: Journal of agricultural and food chemistry, Issue: Vol 50, Issue 10, May 2002

3) Characterization of red raspberry (Rubus idaeus L.) genotypes for their physicochemical properties.

https://doi.org/10.1111/j.1750-3841.2009.01297.x

4) Nonsense Mutation Inside Anthocyanidin Synthase Gene Controls Pigmentation in Yellow Raspberry (Rubus idaeus L.).

https://doi.org/10.3389/fpls.2016.01892


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