Search

Sensory properties are an essential quality aspect when the consumption of fresh tomato is under consideration. The flavor of tomato is defined as a combination of taste sensations (sweetness, sourness), aroma (volatile compounds), and texture (firmness, mealiness), some of which are proven to be affected by insufficient nutrient supply -- especially potassium (K). This study intends to undertake a holistic assessment of the K fertilization effect on the flavor of tomato by connecting the use of sensorial and instrumental methods. An optimal K supply significantly increased the sensory descriptors sweetness, sourness, and aroma as well as the instrumental estimated color, firmness, total soluble solids (TSS), titratable acids (TA), and dry matter (DM) in a cultivar-specific manner. The volatile organic compounds (VOCs) were not significantly affected by K fertilization. The evaluation by the panelists confirmed the results of the instrumental analyses, by which an increment in the fruit quality with rising K supply could be detected. An optimal K supply of 3.66 g/plant could be suggested to increase tomato flavor in the cocktail cultivars studied: Primavera and Yellow Submarine. Cultivar effects should, therefore, be considered for defining the optimal K fertilizer dose that favors high tomato fruit quality and, hence, better flavor. [ABSTRACT FROM AUTHOR]

Tomatoes are an important source of benefcial phytochemicals, which act as antioxidants. These include ascorbic acid, phenolic compounds, carotenoids, and tocopherols. The concentration of anti-oxidants is infuenced, among others, by abiotic stress factors like nutritional status. Potassium (K) is a macronutrient, which is essential for several physiological functions in plants -- for example, translocation of assimilates, activation of enzymes, maintenance of turgescence, and stomata regulation. This study aims to investigate the effect of increasing K fertilization on the concentration of anti-oxidants in cocktail tomatoes. Therefore, two tomato cultivars (Primavera and Resi) grown in an outdoor pot experiment were ferti- lized with increasing K doses for two consecutive years. It has been confrmed that antioxidants in tomato fruit can be affected by the K regime, but it is also shown that other factors may reduce or even reverse those effects when cultivation takes place in an uncontrolled outdoor environment. The most consistent K fertilization effects were found for naringenin, p-coumaric acid, and caffeic acid. However, the enrichment of tomatoes with antioxidants by K fertilization is cultivarependent and therefore general statements should be avoided. [ABSTRACT FROM AUTHOR]

The demand for organically grown tomatoes has rapidly increased on the consumer side. However, there is a lack of tomato cultivars suitable for organic farming that are both high yielding and of superior fruit quality. In the present study, the variation in plant growth and fruit quality of tomato cultivars was assessed to identify the traits associated with higher yield and improved fruit quality. Sixty tomato cultivars, cocktail and salad tomatoes, were grown under organic low-input conditions in 2015 and a subset of 20 cultivars for further evaluation in 2016. The results revealed a high variability among 60 cultivars in all 28 traits that were observed. Salad cultivars that have been selected for intensive indoor cultivation exhibited the highest yield components. A cross-year evaluation of the 20 cultivars showed that salad cultivars had 10-70% lower fruit quality including minerals, dry matter, total soluble solids, and total phenolic compounds (TPC), but 10-60% higher fruit yield and leaf minerals than cocktail cultivars. Cocktail cultivars with improved yield performance were derived from organic breeding. Depending on the cultivar, there was a trade-off between fruit yield and fruit quality. Interestingly, salad cultivars with high magnesium (Mg) concentration in the leaves also contained high Mg concentration in the fruits. Moreover, fruit Mg correlated positively with titratable acidity and TPC of the salad cultivars, as well as with fruit phosphorus, potassium, and sulfur in both cocktail and salad cultivars. The results indicate the contribution of Mg in improving flavor, health related-compound and nutritional quality of tomato fruits. This information provides a novel path for further studies to improve plant-available Mg in organic tomato production to enhance fruit mineral concentration and fruit quality. [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum L.) fruit contain several health beneficial antioxidants [1]. Their contents can be greatly influenced by abiotic factors such as light, temperature, or the nutritional status [2]. The macronutrient potassium (K) is essential for several physiological functions in plants, e. g. translocation of assimilates, activation of enzymes, maintenance of turgescence, and stomata regulation. The aim of the study was to investigate the impact of increasing K fertilization on the antioxidants ascorbic acid, phenolic compounds, carotenoids, and tocopherols in tomatoes. Three cocktail tomato cultivars (Primavera, Resi, and Yellow Submarine) raised in an outdoor pot experiment were treated with five rising K doses in the first study year 2014. In 2015, Primavera and Resi were selected for a subsequent experiment using the lowest and highest K doses. In this experiment, the lipophilic antioxidants were additionally measured in three different tomato ripening stages. Increasing levels of K fertilization distinctly affected the contents of antioxidants in cocktail tomatoes (Table 1). However, most of the effects were not consistent across all three cultivars and the two study years. In 2014, K fertilization level positively correlated (p≤0.05 or 0.01) with ascorbic acid and γ-tocopherol in Resi and with p-coumaric acid in Primavera, while significant negative correlations were observed for narigenin and ß-carotene in Primavera and for β-tocopherol and δ-tocopherol in Yellow Submarine. In contrast, significant positive correlations between K fertilization level and ascorbic acid, p-coumaric acid and caffeic acid were demonstrated for both, Primavera and Resi, in 2015. As opposed to 2014, the tocopherols in Resi and Primavera negatively correlated with increasing K fertilization. The only antioxidant that consistently showed positive correlations with increasing K doses across cultivars and study years was p-coumaric acid. In summary, the content of plant antioxidants in cocktail tomatoes cultivated outdoors can be positively or negatively affected by K fertilization. However, other abiotic factors, such as variation in light and temperature may impact or even inverse those effects [3,4]. [ABSTRACT FROM AUTHOR]

Aroma of fruit is a key indicator to depict the quality of fruit flavor and is likely to play an important role in determining the perception and acceptability of products by consumers [1,2]. Flavor has obviously been targeted as a secondary breeding goal in recent decades [3]. Studies reveal that tomatoes grown under organic conditions positively increase the consumer preference [4]. Therefore, it is necessary for plant breeders who are developing cultivars for organic production to select also for better flavor characteristics. Sixty indeterminate cultivars which differ mainly in terms of fruit weight, year of cultivar release and fruit color were grown in an outdoor organic low-input system in a temperate climate. The diversity of volatile organic compounds (VOCs), taste-related primary metabolites, and sensory properties of ripe tomatoes consisting of 27 cocktail and 33 salad tomato cultivars released between 1880 and 2015 from conventional, organic or unknown breeding programs, were investigated at two different harvest dates in 2015. The volatile compounds of tomato fruits were semi-quantified by GC-FID and tentatively identified by GC-MS. Isolation of volatiles were performed through automated headspace solid-phase microextraction (HS-SPME). A non-targeted data analysis (pattern recognition) was used. The evaluation of the cultivars from the two harvest dates exhibited a wide range of variation for all studied traits, with the exception of a few VOCs. Cultivar × harvest date interaction had no significant effect on TA (titratable acidity), TSS (total soluble solid), or overall acceptability but influenced most of the studied VOCs. Further examination was focused on total of 25 VOCs: 7 aldehydes, 5 ketones, 7 alcohols, 4 aliphatic acids, 1 ester and 1 sulfur-containing compound. The main compounds with the highest value in relative concentration in the headspace of tomato fruits include hexanal, 6-me-5-heptene-2-one, (E)-2-hexenal, octanal, 1- hexanol, etc., of which aldehydes are the most abundant volatile group. Variation in all studied traits like fruit type, harvest time, or fruit color was observed, and the discriminative variables characterizing the fruit types were revealed. Principal component analysis differentiated cocktail and salad types with a higher contribution of taste related-primary metabolites (TSS and TA), sensory attributes (sweetness, tomato typical-aroma, and sourness) and phenyl ethyl alcohol, the latter is a discriminative key compound to distinguish cocktail from the salad type. The observed correlations among the metabolites give cues for their biosynthesis pathway. The presence of VOCs such as (Z)-3-hexen-1-ol, phenyl ethyl alcohol, and benzyl alcohol had effect on the perception of ‘sweetness' and ‘tomato typical-aroma'. Therefore, the present findings should provide a preliminary knowledge for cultivar selection in breeding programs that perform better in flavor and are suitable for organic low-input production systems. [ABSTRACT FROM AUTHOR]

Being a staple food potatoes are grown in many countries with a world-wide production of 380 Mio tonnes in 2014 [1]. In Germany the per capita consumption of potatoes is about 56.8 kg in the financial year 2015/2016 with a share of 60% of processed potatoes [2] such as fried products (e.g. French fries). Industrial processing of French fries includes several steps like quality control of raw material, blanching, par-frying and freezing [3]. End-frying as the last preparation step is mainly done in canteens or at home. In fried products the heatinduced contaminant acrylamide can be formed via the Maillard reaction depending on the amount of the precursors reducing sugars (glucose, fructose) and asparagine [4]. Different NIRS applications have been tested for potatoes during the last decades. Good predictions of the dry matter and starch content have been established by measuring theraw grounded tuber [5]. Potato cultivars used for processing of French fries usually contain a high amount of dry matter that mainly consists of starch. Due to their low concentration, reducing sugars in the raw tuber (3-24 mmol/kg) and likewise, the acrylamide in the deep fat fried product are minor components [4]. NIRS-based predictions of reducing sugars in the raw material would be an advantage in the quality control of industrial French fries processing [5]. However, acceptable predictions for such minor components are hardly reachable [5,6]. Nonetheless, in potato breeding process less exact predictions could be a useful complementation in the phenotyping of new breeding lines. Within a current project (DEPOLA, starting 2017) we try to develop a NIRS model to be usedas a valid screening tool in identifying potato genotypes with a low acrylamide potential. To perform the trial, a set of 185 genotypes from German and Turkish breeding programs is grown in both countries of contrasting climatic conditions. The total sample number will reach at the projects end 1600 including field replications, several locations (three per country) and different storage treatments. Yet, a subset of 96 samples is analyzed. The quality parameters that were used for model development are dry matter, starch, glucose, fructose, sucrose, colour (L*a*b* values) and acrylamide. NIR measurement was repeated twice for each sample and a wavelength range of about 400-2500 nm was monitored with a FOSS XDS NIR spectrophotometer. Most quality parameters show a high variation within the data set, especially for acrylamide but also for the colour (a* value) and the glucose content, which is a basic requirement. Taking into account the size of the sample set a cross validation was performed. Besides, using non-treated spectra that seem to be well suited for the dry matter content (R² of calibration and prediction of 0.97 and 0.96, respectively), the first and second derivatives were used to model the prediction of the minor components. For glucose the R² of calibration and prediction were 0.85 and 0.59 when using the first derivative. By using the second derivative for acrylamide the R² of calibration and prediction were 0.91 and 0.41. The mathematical pre-treatments were able to improve the model indices. Even though the data set was small, it indicates capabilities of NIR technique as a screening tool for breeding purposes. Satisfactory information should be taken from a larger data set that we will gain by the end of the project in 2020. [ABSTRACT FROM AUTHOR]

Copyright of Berichte aus dem Julius Kühn-Institut is the property of Julius Kuehn Institut and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There is evidence that potassium (K) fertilization enhances the yield of medium and large-sized tomato cultivars. Many authors observed positive effects of K fertilization on fruit color, texture, total soluble solids (TSS) and titratable acids (TA) [3, 6]. The market for small-sized cocktail tomatoes is currently growing due to their preferable taste [5] which is positively related to increasing levels of TSS and TA [1, 2, 4]. We hypothesize, that K improves yield and quality of cocktail tomatoes. In order to test our assumption, we carried out pot experiments in two consecutive years. In a pot (6 L) experiment, three cocktail tomato cultivars (Primavera, Resi and Yellow Submarine) were fertilized with five K levels (3.1, 6.3, 9.4, 12.5 and 18.7 g K/pot applied in total over 19 weeks) to find out ideal dosages for well and deficient fertilized plants. Interestingly, the K effect on yield and most quality parameters was highly cultivar specific: while Primavera and Yellow Submarine reached a yield increase of more than 100% from the lowest to the highest K dose, no response of Resi was observed. In contrast to Primavera and Yellow Submarine, Resi showed only weak K fertilization effects on fruit quality aspects. Therefore, in a second experiment we grew the cultivars Primavera and Resi with two K doses (deficient and well-fertilized). In a third treatment, we interrupted K fertilization in order to induce a response in the cv. Resi to a sudden shortage of K. In contrast to Primavera, Resi showed no yield response to K fertilization like in the first experiment. The low yielding cv. Resi seemed to be more K efficient compared to Primavera. We conclude that the effect of K on yield and quality of cocktail tomatoes depends on the cultivar. [ABSTRACT FROM AUTHOR]