Does Refrigeration Always Reduce Tomato Aroma? Four Days of Storage Tested

Should the tomatoes you bring home go into the refrigerator or stay in the kitchen? Hearing that chilling reduces their aroma can make the choice confusing.

A study published in 2020 found that ripe tomatoes stored at 7°C or 20°C for 4 days did not differ significantly in aroma or taste ratings when evaluated at the same serving temperature. The experiment also incorporated time in distribution and retail rather than assuming fruit reached the home immediately after harvest. Alongside storage conditions, the type of tomato proved important.

Following tomatoes from harvest to the table

Larissa Kanski and colleagues at the University of Göttingen in Germany asked how brief household storage affects tomato flavor. Tomatoes bought in shops have already spent time in distribution and retail. The researchers wanted to include that earlier part of the journey.

The study had three aims: to compare freshly harvested fruit with fruit that had passed through simulated distribution and two household-storage conditions; to compare new breeding lines with their parental cultivars; and to examine how well an analytical instrument called an electronic tongue could capture human assessments of sweetness and sourness.

Tomato flavor combines sweetness from sugars, sourness from acids and aromas detected through the nose. The team therefore measured not only volatile aroma compounds but also sugars, acids, pigments, firmness and other properties, comparing these with assessments made by people tasting the fruit.

Five ripe tomato types, stored at 7°C and 20°C for 4 days

The researchers used 3 cultivars, Black Cherry, Primabella and Roterno F1, plus 2 breeding lines obtained by crossing Black Cherry with each of the other cultivars. These 5 types ranged from smaller-fruited to salad tomatoes. Each was grown in 4 independent cultivation replicates, and fruit was harvested ripe after its color was checked.

The storage sequence was standardized as follows:

1. 1 day at 12.5°C to represent distribution
2. 2 days at 20°C to represent retail display
3. A further 4 days at either 7°C or 20°C to represent household storage

Both sequences lasted 7 days from harvest. Humidity also differed in the final household stage: 85% at 7°C and 55% at 20°C. The study compared two simulated household situations, not temperature alone.

Aroma compounds were analyzed using gas chromatography and related techniques to separate and detect them. Changes before and after storage were examined for 18 compounds confirmed using standards. In addition, 12 trained assessors evaluated green odor, tomato odor and flavor, sweetness, sourness, juiciness, skin firmness and aftertaste.

Importantly, refrigerated fruit was brought back to room temperature before tasting. This was not a comparison between cold tomatoes straight from the refrigerator and room-temperature fruit. Tomatoes were cut immediately before serving, and each sample was evaluated twice.

Cultivar characteristics stood out more than storage conditions in aroma and taste

Human assessments found no significant differences between storage at 7°C and 20°C. Comparing freshly harvested and stored fruit also revealed no significant storage effect in the sensory evaluations.

Cultivar and breeding-line differences, on the other hand, were clear. Black Cherry and its cross with Primabella, for example, received high sweetness ratings regardless of storage conditions. Chemical analysis also placed these two among the types with high fructose and glucose concentrations.

An analysis combining several sensory attributes likewise tended to group samples of the same cultivar close together despite different storage conditions. Within the conditions tested, the underlying cultivar or breeding line was more strongly reflected in flavor differences than whether the final 4 days were spent refrigerated or at room temperature.

Not everything measured remained constant, however. Stored fruit became redder and softer than freshly harvested fruit. The tabulated firmness values also differed between 7°C and 20°C for some cultivars or breeding lines. Sensory flavor ratings and individual instrumental quality measures need to be read separately.

Aroma compounds do not all rise or fall together

Closer inspection of the chemical measurements showed that changes during storage depended on both the molecule and the tomato type. For instance, the relative amount of hexanal, associated with green or grassy aromas, increased under both storage conditions in Primabella and Black Cherry × Primabella compared with harvest. In Black Cherry it increased at 20°C, but the same change did not occur uniformly in all types.

Benzaldehyde, in contrast, tended to decrease in every type under both storage conditions, with some decreases statistically significant. These comparisons were based on proportions of the total detected volatile compounds. An increase in hexanal therefore cannot simply be translated into stronger overall tomato aroma.

These molecules have pathways of formation from other constituents of the fruit. Some six-carbon aroma compounds, including hexanal, derive from fatty acids such as linoleic and linolenic acids. β-Ionone, meanwhile, is an aroma compound formed through breakdown of the pigment β-carotene.

In this study, Primabella had more β-carotene and β-ionone than the other types, and the two were positively correlated. An interesting feature of the work is its examination of cultivar-related aroma differences through both odor compounds and the substances from which they arise.

How closely did the electronic tongue match human sweetness and sourness ratings?

The team also used an electronic tongue to measure fruit-juice samples with sensors. Correlations between its output and human ratings were 0.82 for sweetness and 0.52 for sourness. Both were significantly positive, with the closer relationship for sweetness.

This suggests a possible supporting role for instrumental measurements when comparing many cultivars and breeding lines. It does not reduce the whole experience of tomato flavor, including aroma and texture, to a single number. It does offer another way to assess sweetness and sourness in research aimed at breeding flavorful tomatoes.

Conditions to consider for tomatoes at home

To apply the findings to everyday life, it helps to look beyond a simple choice between refrigeration and room temperature to ripeness, actual temperature, storage duration and serving temperature.

The study tested 5 types harvested ripe, held through the same simulated distribution sequence and then stored at 7°C or 20°C for 4 days. Lower temperatures, longer storage and ripening green fruit are different conditions. The authors discuss their findings alongside earlier studies reporting flavor loss during chilling, taking differences in temperature and duration into account.

Although the fruit was returned to room temperature before tasting, the study did not compare warming times. It cannot establish a procedure such as leaving tomatoes out for a specified number of hours to recover their aroma. The assessors were also a small trained panel, not a broad survey of consumer preferences.

A nonsignificant result means that this experiment did not detect a difference. Recognizing that scope makes it possible to hold both findings in view: no refrigeration-related flavor loss was detected during this short storage period, while different conditions could produce different results.

Conclusion

In this experiment simulating the journey from distribution to the home, ripe tomatoes stored at 7°C or 20°C for 4 days did not differ significantly in aroma or taste when evaluated at room temperature. Differences between cultivars and breeding lines were clear, however, and chemical changes also depended on tomato type. Electronic-tongue measurements corresponded with human sweetness and sourness ratings, offering an additional supporting tool for selecting flavorful cultivars.

Whether a tomato was refrigerated is not the only clue to its flavor. Which tomato was it, how ripe was it at harvest, and what sequence of times and temperatures did it experience before eating? Following that journey gives a more nuanced picture of the relationship between storage and aroma.

The research was carried out as part of the PETRA^q+n project, supported by Lower Saxony’s Ministry of Science and Culture in Germany. The authors declared no commercial or financial relationships that could constitute a conflict of interest.

References

• Kanski, L., Naumann, M., & Pawelzik, E. (2020). Flavor-Related Quality Attributes of Ripe Tomatoes Are Not Significantly Affected Under Two Common Household Conditions. Frontiers in Plant Science, 11, 472. DOI and full research article.