The influence of pre and post harvest calcium applications on storage capability and quality of Hayward kiwifruit Justina Franco 1, Dulce Antunes 2, F. Melo 1, R. Guilherme 1, Nuno Neves 3, Fátima Curado 3 and Sandra Rodrigues 4 1 ESAC Escola Superior Agrária de Coimbra, Bencanta, 3040-316, Coimbra, PORTUGAL, E-mail: jfranco@mail.esac.pt 2 Faculdade de Engenharia de Recursos Naturais, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, PORTUGAL 3 DRAPC Direcção Regional de Agricultura e Pescas do Centro, Av. Fernão de Magalhães, 465, 3001-955 Coimbra, PORTUGAL 4 KIWICOOP Cooperativa Frutícola da Bairrada, C.R.L., Malhapão, Oiã, 3770 Oliveira do Bairro, PORTUGAL Abstract: The benefits of calcium applications pre and postharvest on fruit storage ability are well know. It was objective of this work to study the effects of calcium preharvest application in two different forms and calcium chloride application postharvest on Hayward kiwifruit storage ability. The present paper reports of experimental results, corresponding to the experimental period from 2005 to 2006. Three application of 0.1% calcium chloride or calcium chelate were made by spraying on the tree at fruit set (beginning of June), July and September. After harvest (beginning of November) half fruits were dipped for 2 min in a solution of 3% CaCl 2. The other fruit were untreated. All fruit were then stored at 0ºC and relative humidity of about 90-95%. Only fruit of the size range 85-105g were analysed and discussed. Measurements of firmness, soluble solids content (SSC) and ascorbic acid were done after 1, 4 and 6 months storage. Kiwifruit sprayed with calcium and dipped in 3% CaCl 2 softened slower and the degradation of ascorbic acid content was lower. Ca-quelate performed better than calcium chloride as preharvest spraying, so it should be considered instead of CaCl 2 to avoid the negative effects of chloride, although our concentrations were very low. Key words: - Actinidia deliciosa, calcium, postharvest, firmness, SSC, ascorbic acid content. 1 Introduction In Portugal kiwifruit production become important from the 1980s. Production is almost exclusively of the cultivar Hayward because of its longer storage life and its larger fruit size. Kiwifruit can be air-stored for 4 to 6 months at 0ºC, although extensive softening will occur [1]. Sustainability of kiwifruit production is also related to their storage ability in order to feed the market all year around as required by consumers. The calcium plays a significant role in maintaining quality in a number of different fruits [5]. The pre and postharvest application of calcium salts has been used successfully in many fresh fruits to reduce loss of firmness and to slow down the ripening process [11]. Calcium alters intracellular and extracellular processes which retard ripening exemplified by lower rates of colour change, softening, CO 2 and ethylene production, increase in sugar and a reduction in total acid content [3]. The benefits of preharvest calcium chloride and calcium chelate applications on retarding kiwifruit firmness during storage have been mentioned in bibliography [4] [12]. The ascorbic acid content is important in fresh fruits and kiwifruit has higher concentration than other fruits. The ascorbic acid content decreased during ripening and storage. There is a reduction of approx. 50-60% during storage [10]. Monolopoulou and Papadopoulou [7], in their research, obtained too a decrease in ascorbic acid content in four varieties of kiwifruit through storage. The objective of this work was to study the effects of calcium preharvest application in two different forms and calcium chloride application postharvest on Hayward kiwifruit storage capability and fruit quality. 2 Material and Methods 2.1 Plant material and treatments The study was based in a Hayward kiwifruit vine orchard installed in the Portuguese Region of Bairrada, corresponding to the experimental period from 2005 to 2006. Some plants were sprayed with
0.1% CaCl 2 or 0.1% Ca-chelate at three times during the growing season (fruit set-end of June, 1 month after fruit set-end of July, and 1.5 month before harvest-middle of September). Fruits were harvest at the beginning of November and immediately transferred to a storage room at 0ºC. After one month, fruits free of defects were selected and separated according to predetermined sizes: (65-75g), (75-85g), (85-105g) and 105g. The fruits of calibre 85-105g were used for experiments. were identified as follow: T1 (control-no Ca spray or dips), T2 (kiwifruit sprayed with 0.1% CaCl 2 and no Ca dips), T3 (kiwifruit sprayed with 0.1% Ca-chelate and no Ca dips); T4 (Kiwifruit with no Ca sprays + dipping in 3% CaCl 2 post harvest); T5 (Kiwifruit sprayed with 0.1% CaCl 2 + dipping in 3% CaCl 2 post harvest); T6 (Kiwifruit sprayed with 0.1% Ca-chelate + dipping in 3% CaCl 2 post harvest). Dips were done for 2 min in a solution of 3% CaCl 2 and then fruits were allowed to dry ant room temperature and placed in the cold room at 0ºC and 90-95% relative humidity. Ten fruits per replication were removed from storage in beginning of, and, for measurements of flesh firmness, soluble solids content (SSC) and ascorbic acid content. 2.1 Measurements Flesh firmness was recorded by digital puncture (model Tr Italy) fitted with a flat-8mm diameter tip. The tip was inserted after skin removal, at the fruit equator, in opposite sides, to a depth of 7mm. The SSC were measured using a digital Atago refractometer (model PR1-Atago Co. LTD, Japan) in juice obtained by squeezing, homogenizing and filtrating peeled fruits. Ascorbic acid was measured as described previously [8], by HPLC (Beckman) equipped with a System Gold Programmable Detector Module 166- UV-Vis (Beckman Coulter, USA), using a Lychrospher RP-18 column (25 cm X 4 cm i.d.; 5µm particle size). The mobile phase was 20 mm NaH 2 PO 4 and the flow rate was 1 ml/min. 2.3 Statistical analysis Statistical analyses were carried out with a SPSS statistical package. Two-way analyses of variance (ANOVA) tests and Duncan s Multiple Range Tests at (P<0.05) for comparisons between treatments over time were conducted. 3 Results and discussion 3.1 Firmness Kiwifruit of 2006 harvest were harder after 1 month storage than the ones of 2005, because they were firmer at harvest (Fig. 1). In both years, kiwifruit softened during storage in the same way. Fruit had a great decrease in firmness from to and slower thereafter. This is in accordance with previous studies [1]. After there were no significant differences in firmness between years. 3.50 3.00 2.50 1.50 0.50 1.80 1.60 1.40 1.20 0.80 0.60 0.40 0.20 1.80 1.60 1.40 1.20 0.80 0.60 0.40 0.20 2005 2006 Figure 1. Firmness of Hayward kiwifruit (size 85-105g) during storage at 0ºC, subjected to the treatments: T1 (control-no Ca spray or dips), T2 (kiwifruit sprayed with 0.1% CaCl 2 and no Ca dips), dips); T4 (Kiwifruit with no Ca sprays + dipping in 3% CaCl 2 post harvest); T5 (Kiwifruit sprayed with 0.1% CaCl 2 + dipping in 3% CaCl 2 post harvest); T6 (Kiwifruit sprayed with 0.1% Ca-chelate + dipping in 3% CaCl 2 post harvest).
In there was no effect of the different treatments on fruit firmness. After 4 months storage (), the fruits of T1 and T2 were firmer than the other treatments. However, at the end of storage period () the fruits of T3, T4 and T6 were the firmest while, T1 (control) and T2 were the softest (Fig. 1). Pre and post harvest calcium application to fruit tissues delayed softening and ripening, by retarding disintegration of cell walls [9]. The calcium ions make bridges between peptic molecules in the middle lamella being responsible for cell cohesion [6]. During storage, fruits sprayed with Ca-chelate or dipped in CaCl 2 softened slower than fruit not treated. Previous studies showed similar results with kiwifruits dipped in 2% CaCl 2 [1]. Gerasopoulos et al. [4] found that three preharvest applications of 0.375% CaCl 2 enhanced firmness during storage. Xie et al. [12] also reported a benefit on kiwifruit firmness during storage by preharvest application of 200ppm Ca-chelate. However, it seems that these concentrations were too low and need to be increased to retard ripening of kiwifruit during storage. In the present experiment it was found that dipping kiwifruit in 3% CaCl 2 was better for maintaining firmness during storage. Hopkirk et al. [5] tested concentrations from 2 to 5% with benefit to kiwifruit firmness, but found severe pitting on fruit dipped in 5% CaCl 2. In our studies, fruit quality wasnot affected by 3% CaCl 2. Also spraying with Caquelate seems to be better in preserving firmness than CaCl 2. 3.2 Soluble solids content (SSC) The SSC increased mostly in the first 2 months storage and remained almost constant for all treatments (Fig. 2). This is in agreement with previous studies [1]. Results in our experimental conditions showed no significant effect of spraying with CaCl 2 or Cachelate or dips in 3% CaCl 2, in SSC, except that treatment T6 (Kiwifruit sprayed with 0.1% Ca-chelate + dipping in 3% CaCl 2 post harvest) had slightly lower SSC at the end of storage (6 months). Antunes et al. [1] referred that kiwifruits dipped in 2% CaCl 2 postharvest showed too slightly lower SSC after 6 months at 0ºC. 1 1 1 1 1 1 1 1 1 2005 2006 Figure 2. Soluble solids content (SSC) of Hayward kiwifruit (size 85-105g) during storage at 0ºC, subjected to the treatments: T1 (control-no Ca spray or dips), T2 (kiwifruit sprayed with 0.1% CaCl 2 and no Ca dips), T3 (kiwifruit sprayed with 0.1% Ca-chelate and no Ca dips); T4 (Kiwifruit with no Ca sprays + dipping in 3% CaCl 2 post harvest); T5 (Kiwifruit sprayed with 0.1% CaCl 2 + dipping in 3% CaCl 2 post harvest); T6 (Kiwifruit sprayed with 0.1% Ca-chelate + dipping in 3% CaCl 2 post harvest).
3.3 Ascorbic acid content During storage ascorbic acid content had a great decrease in all treatments (Fig. 3). The decrease was higher from to, as for firmness decrease, with ascorbic acid content variations of about 60% and slower thereafter. 0 0 0 Figure 3. Ascorbic acid content of Hayward kiwifruit (size 85-105g) during storage at 0ºC, subjected to the treatments: T1 (control-no Ca spray or dips), T2 (kiwifruit sprayed with 0.1% CaCl 2 and no Ca dips), dips); T4 (Kiwifruit with no Ca sprays + dipping in 3% CaCl 2 post harvest); T5 (Kiwifruit sprayed with 0.1% CaCl 2 + dipping in 3% CaCl 2 post harvest); T6 (Kiwifruit sprayed with 0.1% Ca-chelate + dipping in 3% CaCl 2 post harvest). Results are for the year 2005. In there were no significant effects on ascorbic acid content among treatments, although fruit spayed with Ca-chelate had higher ascorbic acid, but in the behaviour was different. dips), T5 (Kiwifruit sprayed with 0.1% CaCl 2 + dipping in 3% CaCl 2 post harvest) and T6 (Kiwifruit sprayed with 0.1% Ca-chelate + dipping in 3% CaCl 2 post harvest) had a higher significant ascorbic acid content than T1 (control) with the lowest values. At the end of the storage life () the treatments T4 (Kiwifruit with no Ca sprays + dipping in 3% CaCl 2 post harvest) and T6 (Kiwifruit sprayed with 0.1% Cachelate + dipping in 3% CaCl 2 post harvest) had the highest ascorbic acid content and T1 (control) had the lowest (Fig. 3). The ascorbic acid content decreased during ripening and storage. There was a reduction of approx. 50-60% during storage [10]. Manolopoulou and Papadopoulou [7], in their research, obtained too a decrease of ascorbic acid content through storage. This work suggest that Hayward kiwifruit preharvest sprayed with Ca-chelate and postharvest application with CaCl 2 was beneficial in retarding degradation of ascorbic acid content. 4 Conclusion Results obtained in our experimental conditions indicate that fruit quality was better in kiwifruit sprayed with Ca-chelate and dipped in 3% CaCl 2. At the end of the storage kiwifruit softened slower and were higher ascorbic acid content, two important parameters of quality. The concentrations used in this experiment are not considered harmfull for the environment and human health. However, since Ca-chelate performed better than CaCl 2 as pre-harvest spraying, further studies should be done on the use of higher concentrations of Ca- chelate as spraying to reduce or avoid chloride applications as CaCl 2. Also other forms of Ca as calcium chelate or calcium carbonate are being tested for us as dips. Acknowlegments We would like to acknowledge the staff of both the Escola Superior Agrária de Coimbra (Dep. Fitotecnia), Kiwicoop and ex- Direção Geral de Agricultura da Beira Litoral, for their collaboration in the field work and for laboratory analysis. The study was financially supported by the research project AGRO 688/04. References: [1] Antunes, M.D.C., Neves, N., Curado, F., Rodrigues, S., Franco, J. and Panagopoulos, T.,
The effect of calcium applications on kiwifruit quality preservation during storage. Acta Hort., 753, 2007, pp 727-732. [2] Antunes, M.D.C and Stakiotakis, E. M., Ethylene bioynthesis and ripening behaviour of Hayward kiwifruit subjected to some controlled atmospheres. Postharvest Biol. Technol, 26, 2002: pp 167-179. [3] Conway, W. S., The effects of postharvest infiltration of calcium, magnesium or strontium on decay, firmness, respiration and ethylene production in apples. J. Am. Soc. Hortic. Sci, 112(2), 1987, pp 300-303. [4] Gerasopoulos, D., Chouliaras, V. and Lionakis, S., Effects of preharvest calcium chloride sprays on maturity and storability of Hayward kiwifruit. Post. Biol. Technol., 7, 1996, pp 65-72. [5] Hopkirk, G., Harker, F. R. and Harman, J.E., Calcium and firmness of kiwifruit, NZJ. Crop. Hort. Sci, 18, 1990, pp 215-219. [6] Knee, M.; Bartley, I. M., Composition and metabolism of cell wall polysaccharides in ripening fruits. In: J. Friends and M.J.C. Rhodes (editors). Recent advances in the biochemistry of fruits and vegetables. Academic Press. London and New York, 1981, pp 133-148. [7] Manolopoulou, H. and Papadopoulou, P. A study of respiratory and physico-chimical changes of four kiwifruit cultivars during cool-storage. Food Chemistry, 63 (4), 1998, 529-534. [8] Miguel, G., Dandlen, S., Antunes, D., Neves, A. and Martins, D. The effect of two methods of pomegranate (Punica granatum L.) juice extraction on quality during storage at 4ºC. J. Biomed. Biotech., 5, 2004, 332-337. [9] Roy, S.; Conway, W.S.; Watada, A.E.; Sams, C.E.; Pooley, C.D. ; Werning, W.P., Distribution of the anionic sites in the cell wall of apple fruit after calcium treatment. Quantification and visualization by a cationic colloidal gold probe. Protoplasma. 178, 1994, pp 156-167. [10] Sass, P., Fruit storage, Ed. Árpád Aranyossy. Budapest, 1993. [11] Souty, M.; Reich, M.; Breuils, L.; Chambroy, Y.; Jacquemin, G.; Audergon, J. M., Effects of Postharvest Calcium on Shelf-life and Quality of Apricot Fruit. Acta Hort., 384, 1995. pp 619-623. [12] Xie, M., Jiang, G.H. and Kawada, K., Effect of preharvest Ca-chelate treatment on the storage quality of kiwifruit. Act. Hort, 610, 2003, pp 317-324.