Effects of Ripening Stage and Storage Time on Quality Parameters of Red Raspberry Fruit

Transcription

1 Europ.J.Hort.Sci., 68 (4). S , 2003, ISSN Verlag Eugen Ulmer GmbH & Co. Stuttgart Effects of Ripening Stage and Storage Time on Quality Parameters of Red Raspberry Fruit Erika Krüger 1), Evelin Schöpplein 2), Sabine Rasim 1), Giuseppina Cocca 3) and Heike Fischer 3) (The Geisenheim Research Institute, 1) Department of Pomology, 2) Department of Beverage Technology and 3)Fachhochschule Wiesbaden-University of Applied Sciences, Geisenheim, Germany) Summary Zusammenfassung The effects of ripening stage and storage time on quality parameters of red raspberry fruit of cvs. Resa, Rumiloba, Tulameen and Schönemann were investigated. The ripening stages semi-ripe, ripe and slightly over-ripe were defined by CIE L*a*b* colorimetric measurements. Fruits were stored at 0 d, 1 d at 20 C room temperature and 3 d at 2 4 C followed by 1d at room temperature, respectively. The parameters firmness, titratable acidity and fruit colour were strongly affected by ripening stage. Storage had a strong effect on the content of soluble solids and the suitability for shipping. Cultivar effects are presented. The sensory descriptive analysis showed an effect of progressed ripening on odour and taste, whereas storage time resulted in small effects, only. Popularity of fruits strongly correlated to attributes like sweetness, sweetness:acidity ratio and fruity taste. Despite low values in the evaluation of the fruits, the attribute untypical/strange was strongly negatively correlated to the popularity. Differences between cultivars are demonstrated. Interactions existed between cultivar x storage time and ripening stage x storage for firmness, suitability for shipping and some sensory parameters. This shows that semi-ripe fruits could have an improved suitability for shipping depending on the cultivar. However the taste of semi-ripe fruits should be considered. Einflüsse von Reifeentwicklung und Lagerzeit auf die Qualität von Himbeeren. Bei den Himbeersorten Resa, Rumiloba, Tulameen und Schönemann wurden die Einflüsse von Reifeentwicklung und Lagerzeit auf die Qualität der Früchte untersucht. Die Reifestadien halbreif, reif und hochreif wurden mittels CIE L*a*b*-Farbmessungen definiert. Die Früchte wurden wie folgt gelagert: 0 d (Frischware), 1 d bei 20 C Zimmertemperatur und 3d bei 2 4 C plus 1d Zimmertemperatur. Die Parameter Fruchtfestigkeit, Gehalt an Gesamtsäure und Fruchtfarbe wurden am stärksten durch die zunehmende Reifeentwicklung beeinflusst. Die Lagerung übte dagegen einen starken Einfluss auf den Gehalt an löslicher Trockensubstanz und die Verkaufsfähigkeit der Früchte aus. Sorteneinflüsse werden dargestellt. Die deskriptive Sensorik ergab einen wesentlichen Einfluss der Reife auf Geruchs- und Geschmacksparameter, während die Lagerung nur zu geringen Veränderungen führte. Die Beliebtheit der Früchte war stark positiv mit den Attributen Süße, Zucker:Säure-Verhältnis und fruchtig korreliert. Das Attribut untypisch/fremd erreichte in der Bewertung nur ein sehr geringes Niveau, war aber dennoch stark negativ mit der Beliebtheit der Früchte korreliert. Sortenunterschiede in der sensorischen Bewertung werden aufgezeigt. Wechselwirkungen zwischen Sorte x Lagerung und Reife x Lagerung für die Parameter Festigkeit, Verkaufsfähigkeit und einigen sensorischen Eigenschaften geben Hinweise darauf, dass halbreif geerntete Früchte sortenabhängig eine bessere Verkaufsfähigkeit auch nach Lagerung aufweisen könnten. Hierbei darf der Geschmack der halbreifen Früchte allerdings nicht unbeachtet bleiben. Key words. sensory descriptive analysis fruit colour fruit firmness internal quality Introduction Fresh red raspberries are aromatic fruits, appreciated by consumers, and contain healthy dietary compounds with antioxidant capacity (ANCOS et al. 1999, 2000; KALT et al. 1999; WANG and LIN 2000). Their limited shelf-life is due to their fast respiration, loss of firmness, susceptibility to post-harvest fruit rot and darkening. Several attempts were made to extend the shelf-life of raspberry fruits by defined storage conditions or modified atmosphere (MA) packaging (DIEREND et al. 1998; VAN DER STEEN et al. 2001). However, the stage of maturity at harvest largely affects the shelf-life of raspberries, their storage behaviour and sales probability. Since raspberry is a non-climacteric fruit, there is no objective parameter for its optimal ripening stage with

2 Krüger et al.: Effects of Ripening Stage and Storage Time on Quality Parameters of Red Raspberry Fruit 177 regard to its shelf-life available. Fruit colour was suggested as a maturity index using terms such as interception, red ripe, processing ripe (SJULIN and ROBBINS 1987; HEIBERG 1988) or commercial maturity (AGRAR et al. 1997; ANCOS et al. 1999). Studies on the influence of maturity at picking or subsequent storage conditions provide information on quality parameters, such as fruit firmness, titratable acidity, total soluble solids (TSS) and anthocyanin concentration. The impact of these four factors on taste and sensory attributes of raspberry fruits are obscure with poor correlation with sensory perception (BRENNAN et al. 1997). The purpose of this study was to determine the effect of three objectively measured maturity stages and three storage intervals on physical and chemical quality parameters as well as on sensory characteristics of red raspberry fruits of four cultivars. Materials and Methods Red raspberry fruits were picked in Geisenheim from four cultivars, Resa, Rumiloba, Schönemann, and Tulameen twice a week during their midseason harvest period in 2000 to The first three varieties are German cultivars. Tulameen was bred in Canada. Fruits were separated into three maturity stages representing semi-ripe, ripe and slightly over-ripe, respectively, as found in a picking bin. All fruits were measured at the two harvest dates with a portable tristimilus Lab-colorimeter (Chroma-Meter CR 200, Minolta, Germany, calibrated to a standard white reflective plate with L*=97.93, a*= 0.34, b*= 2.27, standard illumination C) to separate the different ripening stages according to the CIE L*a*b*-values shown in Table 1. L*a*b*-values were used to calculate chroma (C) (C =[(a*) 2 +(b*) 2 ) 0.5 ] = colour saturation) and hue angle (h) (h=arctan b*/a*) as recommended for measurements of colour changes in food (HUNG 1990). The three storage conditions used were based on those in which raspberries are often kept from harvest via supermarket to consumers: 0-day, 1-day at 20 C, and 3-days at 2 4 C, and % RH followed by 1-day at 20 C (3+1 d). A sample of 50 fruits was used for each harvest date and each combination of cultivar, maturity stage and storage time to evaluate loss of fresh weight, fruit firmness, tritrable acidity, and total soluble solids (TSS), with a sub-sample of 30 fruits for sensory examination. Weight loss largely due to transpiration and, to a lesser extent, respiration of the fruits was expressed as percentage of the berry weight at harvest. Fruit firmness was measured using a small fruit penetrometer (Fruit Pressure Tester FT 011, Gullimex) fitted with a 4.0 cm 2 perspex contact plate, placed at a right angle on the fruits to measure exudation (force to exude juice from the fruit) which was visible through the Perspex and expressed as Newton (mn) (BARRITT and TORRE 1980). To determine darkening, the colour of each fruit of the stored samples was measured again with the Chroma-Meter CR 200. Fruit still suitable for selling i.e. excluding fruits with softening and bruising were assessed after storage for their appearance. Fruit rot did not occur. Fruits were frozen at 20 C and thawn over night, ground, and blended with 50 µl pectolytic enzymes (Rohapect MA Plus AB Enzymes, Darmstadt), heated up to 45 C for 30 min in a water bath, and centrifugated at g for 15 min. Acidity was determined by titration of 5 ml fruit juice with 0.3 mol L 1 NaOH to ph 8.1 and expressed as g L 1 citric acid. Total soluble solids were estimated with a digital refractometer and expressed as % Brix at 20 C. Raspberry fruit of each cultivar and maturity stage were subjected to sensory tests after 0-day, 1-day and 3+1 days storage by a trained tasting panel consisting of a minimum of eight assessors using descriptive analysis. The following attributes were evaluated: colour intensity, for odour the attributes unripe/green, fruity, flowery, musty, untypical/strange and for taste the attributes sweetness, acidity, ratio sweetness:acidity, fruity, juicy, untypical/strange and firmness. The score of each panellist was recorded by marking a position on a 10 cm line, with extreme values of each attribute representing the absence (0) or very strong expression (10) of each attribute. In parallel to descriptive analysis general popularity of the fruits was assessed. Statistical analysis Data were statistically analysed with a threefactorial Anova to evaluate the main effects of cultivar, ripening stage and storage time. The Scheffé-test was applied to verify statistical differences within or between the three factors. Correlations were calculated for popularity to the other taste attributes. Results and Discussion Chemical and physical quality parameters Table 2 shows berry weight, weight loss, fruit firmness and suitability for selling. Table 1. CIE L*a*b*-values from colorimetric measurements used in the study to distinguish between the three different ripening stages of four cultivars of red raspberry fruits. CIE L*a*b*-value semi-ripe ripe slightly over-ripe L* a* b* L* a* b* L* a* b* Resa Rumiloba Schönemann Tulameen deviation ±2.1 ±2.9 ±2.8 ±1.5 ±2.8 ±1.8 ±1.3 ±2.3 ±1.1

3 178 Krüger et al.: Effects of Ripening Stage and Storage Time on Quality Parameters of Red Raspberry Fruit Table 2. Main effects of cultivar, ripening stages and storage time on quality parameters of red raspberry fruits. Main effects Berry weight (g) Weight loss (%) Firmness (mn) Soluble solids % Brix Acidity (g/l citric acid) Suitability for shipping (%) Cultivar Resa 3.0 a 5.6 a 620 b 9.3 a 16.4 a 77.6 b (C) Rumiloba 3.4 b 4.3 c 486 a 11.1 b 22.3 b 63.4 a Schönemann 2.9 a 5.2 ab 524 ab 9.3 a 20.9 b 55.7 a Tulameen 3.0 a 4.6 bc 881 c 13.4 c 25.6 c 82.2 b Ripening stage semi-ripe 2.7 a 4.9 ab 930 c 10.5 a 25.2 c 78.1 b (R) ripe 3.2 b 4.5 b 586 b 10.9 a 21.2 b 73.0 b slightly over-ripe 3.3 b 5.3 a 367 a 10.9 a 17.6 a 58.1 a Storage 0 day 0 c 732 b 10.4 a 21.9 a c (S) 1 day 5.0 b 599 a 10.9 ab 21.2 a 63.1 c 3 and 1 day 9.8 a 553 a 11.1 b 21.0 a 46.1 a Interaction C x R ns ns *** ns ns ns C x S ns ** *** ns ns *** R x S ns ns ** ns ns *** ns, **, *** non significant or significance from Scheffé test at p < 0.01 or 0.001, respectively Berry weight on the vine increased from the semi-ripe to the ripe stage, only. In the literature, a constant increase in fruit weight during ripening on the vine can be found (SJULIN and ROBBINS 1987), as well as an increase from the pink to the red ripe stage, only (IANNETTA et al ) The recorded differences between the ripening stages in this experiment would mean an increase in yield of about 18.5 % over time. Rumiloba was the cultivar with the biggest fruits. Storage time had a strong influence on weight loss of the fruits. For the ripening stages weight loss was significantly different only between the semi-ripe and slightly over-ripe fruits. Cultivar effects were detectable with the lowest loss for Rumiloba and the biggest for Resa. However, the percentage of weight loss was very similar. Fruit firmness was different at all ripening stages. Fruits just harvested showed the highest firmness as compared to the two samples with stored fruits. There were also cultivar differences detectable with the highest firmness for Tulameen followed by Resa. The other two cultivars were significantly softer. Internal quality of fruits can be described by the content of soluble solids and titratable acidity. In this study, soluble solids increased during storage and were affected by cultivar and storage time but not by ripening stage. Resa and Schönemann had the lowest and Tulameen the highest content of soluble solids. Titratable acidity was influenced by cultivar and ripening stage. The highest acidity was detected for Tulameen, and the lowest for Resa. Acidity strongly decreased with increasing ripening stage whereas storage time showed no effects. Only fruits just harvested were suitable for selling to 100 %, whereas storage led to a decline. Slightly over-ripe berries had a significant lower suitability for selling than semi-ripe and ripe fruits. The best results were obtained for Tulameen and Resa. Interactions between cultivar and ripening stages were found for firmness, only. Interactions between cultivar and storage time were detected for weight loss, firmness and suitability for selling whereas interactions between ripening stages and storage time was determined for firmness and suitability for selling. These results show that beside genotypes, the ripening stage has a major effect on quantitative and qualitative quality parameters of raspberry fruit. Factors such as weight loss, firmness and selling suitability decrease with increased ripening. Similar results have been reported previously by SJULIN and ROBBINS (1987) for weight loss and firmness, and ROBBINS et al. (1989) and IANNETTA et al. (1999) for firmness. Cell wall breakdown and enlargement of the mesocarp result in enhanced softening of the druplets and thus of the whole fruit (SEXTON et al. 1997). Changes in firmness during ripening recently have also been explained by increased production of ethylene by the ripening fruit and cell wall modifying enzymes (IANNETTA et al. 1999). Reduced juice leakage was found to be negatively correlated with fruit firmness by CALLESEN and HOLM (1989). Therefore, it is not surprising that the suitability for selling decreased rapidly with advanced ripening and increased storage time. In the literature about internal quality, parameters such as soluble solids increase and adecrease of titratable acidity with advanced ripening can be found (SJU- LIN and ROBBINS 1987, PERKINS-VEAZIE and NON- NECKE 1992). However, the increase of soluble solids is not consistent for single harvest dates (SJULIN and ROB- BINS 1987, HEIBERG 1988). This shows that other factors than ripening stage may influence this parameter. The decrease of titratable acidity during storage was also reported by CALLESEN and HOLM (1989) and ROBBINS et al. (1989). For soluble solids SJULIN and ROBBINS (1987) detected an increase whereas CALLESEN and HOLM (1989) could not find any influence of the ripening stage.

4 Krüger et al.: Effects of Ripening Stage and Storage Time on Quality Parameters of Red Raspberry Fruit 179 The high weight losses after one day at room temperature observed in this experiment can be explained by the high respiration and transpiration rates of raspberries, causing a rapid reduction of their post-harvest quality in general (SALUNKHE et al. 1991). This can be reduced only by low temperature and modified atmosphere during storage. Furthermore, pre-cooling of the fruits to 2 C immediately after harvest was found to be essential for a good post- harvest quality (HEIBERG 1988). Optimal conditions with pre-cooling and storage at 0 C can reduce weight losses to about 1 % per day (SJULIN and ROBBINS 1987; ROBBINS et al. 1989). For the results in our experiment without pre-cooling it can be assumed that the weight loss of about 10 % after 3+1 days was mainly affected by the last 24 h at 20 C whereas the preceeding 3 days at 2 C caused smaller losses. Fruit colour Colour is an important characteristic of a fruit and is genetically determined and subject to changes during physiological evolution. It can also influence the acceptability by consumers who conclude on the freshness of the product based on the colour. In this experiment (Table 3), Schönemann was the least luminous (lowest L*value) and darkest cultivar with less red (low +a* value) and more blue colour (low +b* value) than any other cultivar. Rumiloba had the most luminous, most red and less blue fruits. There were also cultivar differences for chroma (colour saturation) and hue angle. Lightness decreased with advanced ripening and was significantly reduced for both stored samples in comparison to the fresh fruits. During ripening, the fruits became less red and more blue. The same changes could be observed for fresh and stored fruits, indicating, that storage enhances darkening of fruits. Chroma and hue angle decreased also with increased ripening and storage. Enhanced ripening had a stronger influence on colour changes than storage time, which is shown by interactions between ripening stage and storage time for all three L*a*b*-values, chroma and hue. These results are consistent with findings in the literature (ROBBINS and MOORE 1990; PERKINS-VEAZIE and NONNECKE 1992). Moreover, ROBBINS and MOORE (1990) found an increased change in colour at 20 C in comparison to 0 or 4.5 C. Results of sensory descriptive analysis For odour (Table 4) cultivar effects were found on a very low, but detectable level for the attributes unripe/green, musty and untypical/strange. The higher values for the negative attributes musty and untypical/strange for Schönemann showed that this cultivar is different from the others. In this study, ripening stage had the strongest effect on odour. As expected, the value for unripe/green decreased while those for fruity and flowery increased with enhanced ripening. The negative attribute musty also increased with ripening, which is mainly caused by the cultivar Schönemann. This resulted in a significant cultivar x ripening stage interaction. Influence of storage could be detected only for the attribute unripe/green. The results show that the unripe/green odour of the fruits were reduced with longer storage time. Beside the cultivar x ripening interaction for musty there were cultivar x storage interactions for the attribute flowery and cultivar x ripening and cultivar x storage interactions for fruity and flowery. Cultivar main effects were significant for all tasty attributes, popularity and colour (Table 5). The biggest effect was found for popularity. Rumiloba had the highest ranking for popularity, despite the fact, that the other attributes reached intermediate values similar to the ranking of the other cultivars. Schönemann reached the lowest value for popularity which is in correspondence with the lowest value for sweetness, ratio sweetness:acidity, firmness, and the high scores for acidity and untypical/strange. As for olfactory attributes (Table 4), Schönemann also differs for the tasty attributes from the others. Tulameen had the firmest fruits and the fruits of Schönemann were Table 3. Main effects of cultivar, ripening stage and storage time on colorimetric parameters of red raspberry fruits. Main effects L* a* b* Chroma Hue angle Cultivar Resa 30.5 b 27.0 c 10.9 bc 29.1 c 21.5 a Rumiloba 30.6 b 27.0 c 11.2 c 29.3 c 22.0 b Schönemann 27.5 a 22.5 a 8.0 a 24.0 a 19.0 a Tulameen 30.8 b 25.8 b 10.5 b 27.9 b 21.7 a Ripening stage semi-ripe 32.5 c 29.0 c 13.3 c 32.0 c 24.4 c ripe 29.6 b 25.7 b 9.9 b 27.6 b 20.9 b slightly over-ripe 27.6 a 22.0 a 7.1 a 23.2 a 17.9 a storage 0 day 30.7 b 26.6 b 11.8 b 29.2 b 23.2 b 1 day 29.3 a 24.8 a 9.3 a 26.5 a 20.1 a 3 and 1 day 29.6 a 25.3 a 9.3 a 27.0 a 19.8 a Interaction C x R *** *** *** *** *** C x S * * ns * ** R x S *** *** *** *** *** ns, *, **, *** non significant or significance from Scheffé test at p< 0.05, 0.01 or 0.001, respectively

5 180 Krüger et al.: Effects of Ripening Stage and Storage Time on Quality Parameters of Red Raspberry Fruit Table 4. Main effects of cultivar, ripening stage and storage time on odour parameters of red raspberry fruits. Main effects Unripe/Green Fruity Flowery Musty Untypical/ Strange Cultivar Resa 0.94 a 4.45 a 2.23 a 0.37 ab 0.28 a Rumiloba 1.54 b 4.46 a 2.85 a 0.27 a 0.31 a Tulameen 1.05 ab 4.33 a 2.83 a 0.32 ab 0.33 ab Schönemann 0.67 a 4.41 a 2.68 a 0.61 b 0.73 b Ripening stage semi-ripe 2.00 c 3.14 a 1.50 a 0.29 a 0.41 a ripe 0.91 b 4.20 b 2.37 b 0.34 ab 0.38 a slightly over-ripe 0.22 a 5.90 c 4.06 c 0.56 b 0.44 a Storage 0 day 1.31 b 4.39 a 2.61 a 0.32 a 0.33 a 1 day 1.03 ab 4.41 a 2.44 a 0.42 a 0.36 a 3 and 1 day 0.81 a 4.44 a 2.89 a 0.45 a 0.56 a Interaction C x R ns ns * ** ns C x S ns ** * ns ns R x S * ns ns ns ns ns, *, ** non significant or significance from Scheffé test at p< 0.05 or 0.01, respectively dark-red to purple red and thus the darkest in colour as compared to the others. As expected ripening had a strong influence on the different attributes (Table 5). All three ripening stages could be significantly distinguished with increasing values for sweetness, ratio sweetness to acidity, fruity, juicy and colour and decreasing scores for acidity and firmness. Scores for untypical/strange differed significantly from ripe to slightly over-ripe. Popularity rose from semi-ripe to ripe with no further increase to over-ripe fruits despite all other attributes were influenced by increased ripening stage. The sensory attributes evaluated were least affected by storage time as compared to the different ripening stages. However, values rose significantly for the attributes sweetness, juicy, colour and, at a very low level, for untypical/strange with increased storage time, whereas firmness decreased. This result indicates that physiological ripening of raspberry fruits continued under the chosen storage conditions. Popularity was highest for fruits stored for one day and lowest for those stored for three days. For the assessed sensory qualities interactions were significant between cultivar and ripening, cultivar and storage stage and ripening and storage stage for untypical/strange, firmness, and popularity. For untypical/strange these interactions were caused by Schönemann where a significant increase was found at the slightly over-ripe stage with continued storage. All three interactions types for firmness and popularity suggest an individual response of the cultivars at the different ripening stages and storage times. It also shows, that for each cultivar the optimal ripening stage may be different with respect to a subsequent storage. Interactions were also found between cultivar and ripening stage for the attributes colour intensity and fruity, between cultivar and storage time for the attributes acidity and ratio sweetness:acidity and between ripening stage and storage time for the attributes colour intensity and juicy. Popularity in general was highly positively correlated with the attributes sweetness, ratio of sweetness to acidity and fruity. It was negatively affected by untypical/strange taste and to a smaller extent by acidity and firmness (Table 6). As shown in Table 5, popularity increased from semi-ripe to ripe fruits and remained unchanged by a further increase in ripening to slightly over-ripe fruits. This may be explained by the highly negative correlation to untypical/strange taste of slightly over-ripe fruits as compared to the other ripening stages. There is also a similar observation in ranking values for the attribute untypical/strange for stored fruits (Table 5) and the correlation of this attribute to popularity. The high ranking of Rumiloba for popularity can be explained by the high values for sweetness, fruity, juicy (Table 5) and the high correlation between these attributes and popularity (Table 6). Light red cultivars also showed a higher popularity as is demonstrated in this study for Rumiloba and Tulameen (Tables 5 and 6). To our knowledge, there is little information available about more detailed sensory evaluation of raspberry fruits. The recent study of MOREL et al. (1999) assessed mainly the effect of genotype on sensory character of fresh and frozen raspberries. They found cultivar x freezing interactions for the attributes purple, juicy, fruity, sweet and raspberry aroma. Investigations of VARSEVELD and RICHARDSON (1980) examined the effect of storage time and storage temperature on sensory ratings for colour, texture and flavour, only. In their study, scores for colour declined with rising temperatures. Scores for texture rose for storage times up to two days and declined as storage progressed and values for flavour were higher after 1 to 2 days as compared to initial values. HEIBERG (1988) found cultivar differences in appearance, colour intensity and brightness after storage of raspberry fruits and effects of the harvest date on taste and colour intensity. In all investigations the effects of ripening stage on the sensory quality of raspberries are not described.

6 Krüger et al.: Effects of Ripening Stage and Storage Time on Quality Parameters of Red Raspberry Fruit 181 Table 5. Main effects of cultivar, ripening stages and storage time on taste parameters of red raspberry fruits. Main effects Sweetness Acidity Sweetness : Aci dity Ratio Fruity Juicy Untypical/ Strange Firmness Popularity Colour Cultivar Resa 4.8 b 3.9 a 5.2 c 4.2 a 4.4 a 0.9 ab 4.2 b 4.4 b 5.6 b (C) Rumiloba 4.8 b 5.1 b 4.5 b 5.3 b 5.3 c 0.9 a 4.3 b 6.1 d 4.9 a Schönemann 3.4 a 5.7 c 3.3 a 4.4 a 5.0 bc 1.2 b 3.5 c 3.5 a 6.9 c Tulameen 4.8 b 5.6 bc 4.2 b 5.2 b 4.6 ab 0.5 a 4.7 a 5.2 c 5.6 ab Ripening semi-ripe 3.4 a 5.8 c 3.3 a 3.9 a 3.5 a 0.6 a 5.6 a 4.0 a 3.8 a stage ripe 4.4 b 5.1 b 4.3 b 4.7 b 4.9 b 0.7 a 4.1 b 5.2 b 5.6 b (R) slightly over-ripe 5.5 c 4.4 a 5.3 c 5.7 c 6.1 c 1.2 b 2.7 c 5.2 b 7.6 c Storage 0 day 4.3 a 5.0 a 4.2 a 4.6 a 4.4 a 0.5 a 4.8 a 4.9 ab 5.2 a (S) 1 day 4.5 ab 5.1 a 4.4 a 4.9 a 4.9 ab 0.8 a 4.0 b 5.1 b 5.8 b 3 and 1 day 4.6 b 5.1 a 4.2 a 4.9 a 5.3 b 1.2 b 3.6 c 4.4 a 5.9 b Interaction C x R ns ns ns * ns * * ** *** C x S ns * * ns ns * * * ns R x S ns ns ns ns * * ** *** ** ns, *, **,*** non significant or significance from Scheffé test at p< 0.05, p< 0.01 or 0.001, respectively Table 6. Correlation coefficients (r) between popularity and other sensory attributes as influenced by main effects of cultivar, ripening stage and storage time of red raspberry fruits. Main effects Sweetness Acidity Sweetness : Acidity Ratio Fruity Juicy Untypical/ Strange Firmness Colour Cultivar Resa ** ** (C) Rumiloba 0.62** 0.58** 0.65** 0.65** 0.50** * 0.64** Tulameen 0.69** 0.58** 0.68** 0.56** ** 0.56** Schönemann 0.33* 0.35* 0.41* ** Ripening stage semi-ripe 0.67** ** 0.46** 0.40** 0.30* (R) ripe 0.56* * 0.38** * 0.50** 0.43** slightly over-ripe 0.35** ** ** 0.41* 0.47** Storage 0 day 0.72** ** 0.76** 0.63** 0.39** 0.45** 0.38** (S) 1 day 0.54** * 0.50** 0.31* and 1 day 0.45** * 0.43** ** *, ** significance from Pearson test at p < 0.05 or 0.01, respectively. Considering all data assessed in our experiment, sensory quality of raspberry fruits was mainly effected by the ripening stage and to a smaller extend by storage time under the chosen conditions. Suitability for selling declines rapidly with increased ripening stage and progressed storage, indicating that raspberries are very delicate in their post-harvest physiology. Under the chosen storage conditions, even semi-ripe fruits should not be stored and must be sold and consumed immediately after picking. Improved storage conditions with pre-cooling and cooling until consumption could have influenced quality parameters positively. Furthermore, the detected interactions between cultivar x storage and ripening stage x storage for selling suitability indicates that specific cultivars may have a better post-harvest response when picked as semi-ripe fruits with a subsequent storage period. References AGRAR, I.T., J. STREIF and F. BANGERTH 1997: Effect of high CO 2 and controlled atmosphere (CA) on the ascorbic and dehydroascorbic acid content of some berry fruits. Postharvest Biology and Technology 11, ANCOS, B. de, E. GONZALES and M.P. CANO 1999: Differentiation of raspberry varieties according to anthocyanin composition. Z. Lebensm. Unters. Forsch. A 208,

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