Vasconcellea Pubescens Research Articles

Morphological, SSR and ISSR marker based genetic diversity assessment of mountain papaya germplasm in comparison with Carica papaya

The genetic diversity in papaya cultivars is essentially important as it provides the basis for varietal improvement. In this regard a study was initiated to assess the genetic diversity of the commercial Carica papaya cultivars in Sri Lanka and to introduce mountain papaya (Vasconcellea cundinamarcensis), which is reported to contain cold resistance and papaya ring spot virus (PRSV-P) resistant trait. Twenty one accessions of Carica papaya and mountain papaya were assessed by morphological, simple sequence repeat (SSR) and inter simple sequence repeat (ISSR) markers. A total of 33 alleles were generated with an average frequency of 2.5 alleles per marker from 11 SSR and 2 ISSR markers. Morphological and molecular marker based cluster analyses revealed that there was no clear distinction among the C. papaya cultivars grown in different geographical areas in Sri Lanka, while mountain papaya was highly distinct from the other C. papaya accessions. Except three SSR markers, all the other markers were polymorphic between mountain papaya and C. papaya accessions. Of the 33 alleles produced, 12 alleles were common for both C. papaya and mountain papaya indicating the potential relatedness to C. papaya. This investigation revealed both the genetic diversity and the relatedness of mountain papaya with C. papaya so as to use it as a potential source for the improvement of C. papaya by hybridisation.

MOLECULAR EVALUATION OF POTENTIAL RESISTANCE TO PAPAYA RING SPOT VIRUS IN MOUNTAIN PAPAYA (VASCONCELLEA CUNDINAMARCENSIS)

Papaya Ring Spot virus (PRSV) is a devastating viral disease in papaya cultivation in Sri Lanka. It was reported that mountain papaya (Vasconcellea cundinamarcensis) exhibits resistance to PRSV. Therefore, this study was conducted to evaluate the potential resistance to PRSV in mountain papaya to be used in papaya improvement breeding programs. Carica papaya and V. Cundinamarcensis were inoculated with PRSV by mechanical inoculation technique and symptoms were evaluated visually. In order to detect the latent infection, a molecular method was developed. PRSV RNA genome segments were amplified using three sets of primers by RTPCR and an amplicon was sequenced to confirm the identity of PRSV. Functional ability of the cDNA was examined using SAND family protein gene (sand) as the reference gene. According to the results, visual symptoms were not observed in mountain papaya while standard visual symptoms appeared in Carica papaya. Three sets of primers were able to amplify the corresponding amplicons in inoculated Carica papaya and sequencing data confirmed that the amplicon was from PRSV. Negative amplification was observed in mountain papaya from the three sets of primers although sand gene amplification was observed, proving the correct functionality of cDNA. Therefore, it can be concluded that mountain papaya is likely to be resistant to PRSV.

Kiwifruit actinidin digests salivary amylase but not gastric lipase.

Kiwifruit contains the cysteine proteinase actinidin whose strong activity allows kiwifruit to be used as a meat tenderiser. This raises the possibility digestive enzymes, also proteins, are themselves susceptible to degradation by actinidin. Salivary amylase and gastric lipase are exposed to the highest concentrations of actinidin whereas duodenal enzymes are less likely to be inactivated by actinidin due to dilution and inactivation of actinidin by gastric juice. The saliva of six volunteers was exposed to Actinidia deliciosa homogenate and then examined for loss of the starch digesting enzyme, alpha-amylase. In agreement with the known distribution of salivary amylase concentration in saliva, the range of amylase activity within the group of volunteers varied by around 100 fold. Within 5 minutes of incubation of 3 parts saliva to one part green kiwifruit at 37 °C, approximately 85% of the amylase activity was lost. The use of E-64, a selective inhibitor of cysteine proteinases, confirmed that the loss of amylase function was due to actinidin. Amylase protein degradation was followed by SDS-PAGE and western blotting. Recombinant human gastric lipase resisted digestion with kiwifruit even after 30 minutes incubation and remained functionally active after this time period. However, both mountain papaya and pineapple extracts degraded gastric lipase fully during a 30 minutes digestion period. Under conditions where cooked starch is consumed along with kiwifruit it is possible that starch digestion may be retarded whereas lipid digestion in the stomach is unlikely to be affected by kiwifruit consumption.

Field Monitoring of 2010-Tsunami Impact on Agricultural Soils and Irrigation Waters: Central Chile

An in situ post tsunami study was conducted to assess the effect of water management and rainfalls in soil properties and water quality at a low-lying coastal area of central Chile affected by Mw8.8 Earthquake Tsunami the night of 27 February 2010. Soil samples were taken at two depths (0 to 20 and 20 to 40 cm) during 2010 and late 2012. Water quality in a local shallow well was also monitored in 2010 and 2012. High soil salinity was recorded 2 months later than tsunami occurs, closely associated to water-soluble chloride and cations (Cl− > > Na+ > > Ca2+ > Mg2+ > K+), ionic toxicities, and vegetal inhibition (Vasconcellea pubescens) by less available water to plants. An initial reduction in soil pH due to ionic strength and coarse-textured class of soil was observed and the sodium adsorption ratio (SAR) in soil varied between 5.7 and 11.2 (mmol L−1)0.5 showing to be saline. Although SARw values are very high (>18 (mmol L−1)0.5), it does not exist risks of reduction on soil infiltration rates according to ECw (>5 dS m−1) obtained. After 2 years, soil salinity was drastically reduced in the affected areas due to high soil permeability and natural attenuation (rainfalls and leaching effects), with sulfate and bicarbonate concentrations showing excessive values. Further, irrigation water quality returned to pre-tsunami situation, with only levels of sodium slightly exceeding desirable range from health point of view. Finally, it is suggested a proper design of irrigation systems before implementing other management practices.

Floral expression and pollen germination ability in productive mountain papaya (Vasconcellea pubescens A.DC.) orchards

Mountain papaya (Vasconcellea pubescens A.DC.) is described as trioecious in the centers of origin of Ecuador, Colombia, and Peru. However, under cultivation conditions in La Serena (30° S, 70° W), Chile, it is found to be dioecious and monoecious. The objective was to learn about the variations in floral expression of mountain papaya. Flowers from monoecious and dioecious plants were therefore identified and quantified during two seasons. In vitro pollen germination ability was also evaluated based on the factors of site, season, and plant sex. Monoecious plant inflorescences are polygamous; female and male flowers are observed, as well as bisexual flowers that are usually deformed. This condition allows them to be classified as an ambisexual plant. The existence of flowers of different sexes appears to depend on the season; the female dioecious plant is maintained as such, independently of climatic conditions. Pollen from male flowers, from both ambisexual and male plants, germinates 75% in summer, while germination decreases to 56% in spring (P ≤ 0.05). Flowering of female plants coincides with the permanent occurrence of male flowers in ambisexual plants, which ensures pollination without the need for male plants as pollinators in orchards. Based on this information, some management practices and possible lines of research about this species are proposed.

Structural and Affinity Determinants in the Interaction between Alcohol Acyltransferase from F. x ananassa and Several Alcohol Substrates: A Computational Study.

Aroma and flavor are important factors of fruit quality and consumer preference. The specific pattern of aroma is generated during ripening by the accumulation of volatiles compounds, which are mainly esters. Alcohol acyltransferase (AAT) (EC 2.3.1.84) catalyzes the esterification reaction of aliphatic and aromatic alcohols and acyl-CoA into esters in fruits and flowers. In Fragaria x ananassa, there are different volatiles compounds that are obtained from different alcohol precursors, where octanol and hexanol are the most abundant during fruit ripening. At present, there is not structural evidence about the mechanism used by the AAT to synthesize esters. Experimental data attribute the kinetic role of this enzyme to 2 amino acidic residues in a highly conserved motif (HXXXD) that is located in the middle of the protein. With the aim to understand the molecular and energetic aspects of volatiles compound production from F. x ananassa, we first studied the binding modes of a series of alcohols, and also different acyl-CoA substrates, in a molecular model of alcohol acyltransferase from Fragaria x ananassa (SAAT) using molecular docking. Afterwards, the dynamical behavior of both substrates, docked within the SAAT binding site, was studied using routine molecular dynamics (MD) simulations. In addition, in order to correlate the experimental and theoretical data obtained in our laboratories, binding free energy calculations were performed; which previous results suggested that octanol, followed by hexanol, presented the best affinity for SAAT. Finally, and concerning the SAAT molecular reaction mechanism, it is suggested from molecular dynamics simulations that the reaction mechanism may proceed through the formation of a ternary complex, in where the Histidine residue at the HXXXD motif deprotonates the alcohol substrates. Then, a nucleophilic attack occurs from alcohol charged oxygen atom to the carbon atom at carbonyl group of the acyl CoA. This mechanism is in agreement with previous results, obtained in our group, in alcohol acyltransferase from Vasconcellea pubescens (VpAAT1).

Update on gene transfer biotechnology of papaya

Papaya ringspot virus (PRSV) is the most devastating disease of papayas worldwide. For 15 years, since 1998, genetically engineered, PRSV resistant Hawaii papayas, 'Rainbow', 'SunUp', and 'Laie Gold' have been sold locally and 'Rainbow' has been exported to the western US. Following deregulation, it has been exported for eight years to Canada and for three years, on a very small scale, to Japan. Markets like Hong Kong that do not differentiate between non-transgenic products and genetically engineered organisms (GMOs) also import Hawaii GMO papayas. At least fifteen research groups attempted to develop GMO papayas, mostly for PRSV resistance. A majority of the papayas were resistant to their specific PRSV strains; however at least initially China is the only other country to have commercialized transgenic virus resistant papaya. Activity in GMO projects is reduced because of negative publicity and lack of funding, but several projects continue: delayed ripening in Malaysia and the Philippines (field testing); PRSV and Papaya leaf distortion mosaic virus (PLDMV) broad resistance with single, double, and super-constructs in Taiwan; PRSV resistance construct development in Pune, India; multiplication of transgenic plants for PRSV resistance testing in Hainan, China; transformation of papaya for PRSV resistance with a gene from a papaya relative, Vasconcellea pubescens; and the final stages of deregulation of a second PRSV resistant papaya for Florida in the US.

Computational study enlightens the structural role of the alcohol acyltransferase DFGWG motif.

Alcohol acyltransferases (AAT) catalyze the esterification reaction of alcohols and acyl-CoA into esters in fruits and flowers. Despite the high divergence between AAT enzymes, two important and conserved motifs are shared: the catalytic HxxxD motif, and the DFGWG motif. The latter is proposed to play a structural role; however, its function remains unclear. The DFGWG motif is located in loop 21 and stabilized by a hydrogen bond between residues Y52 and D381. Also, this motif is distant from the HxxxD motif, and most probably without a direct role in the substrate interaction. To evaluate the role of the DFGWG motif, in silico analysis was performed in the VpAAT1 protein. Three mutants (Y52F, D381A and D381E) were evaluated. Major changes (size and shape) in the solvent channels were found, although no differences were revealed in the entire 3D structure. Molecular dynamics simulations and docking studies described unfavorable energies for interaction of the mutant proteins with different substrates, as well as unfavored ligand orientations in the solvent channel. Additionally, we examined the contribution of different energetic parameters to the total free energy of protein-ligand complexes by the MM-GBSA method. The complexes differed mainly in their van der Waals contributions and have unfavorable electrostatic interactions. VpAAT1, Y52F and D381A mutants showed a dramatic reduction in the binding capacity to several substrates, which is related to differences in electrostatic potential on the protein surfaces, suggesting that D381 from the DFGWG motif and residue Y52 play a crucial role in maintenance of the adequate solvent channel structure required for catalysis. Graphical abstract Molecular docking, molecular dynamics (MD) simulations and MM-GBSA free energy calculations were employed to obtain quantitative estimates for the binding free energies of wild type Vasconcellea pubescens alcohol acyltransferase (VpAAT1-WT) and the protein mutants. Left VpAAT1 model structure in cartoon representation showing the solvent channel in the middle of the structure. Center, right Changes in shape and structure in the solvent channel of Y52F and D381A mutant proteins, respectively, compared to WT. The results obtained reveal that the interaction between D381 and Y52 residues is important for the maintenance of solvent channel structure.

In-silico analysis of the structure and binding site features of an α-expansin protein from mountain papaya fruit (VpEXPA2), through molecular modeling, docking, and dynamics simulation studies.

Fruit softening is associated to cell wall modifications produced by a set of hydrolytic enzymes and proteins. Expansins are proteins with no catalytic activity, which have been associated with several processes during plant growth and development. A role for expansins has been proposed during softening of fruits, and many fruit-specific expansins have been identified in a variety of species. A 3D model for VpEXPA2, an α-expansin involved in softening of Vasconcellea pubescens fruit, was built for the first time by comparative modeling strategy. The model was validated and refined by molecular dynamics simulation. The VpEXPA2 model shows a cellulose binding domain with a β-sandwich structure, and a catalytic domain with a similar structure to the catalytic core of endoglucanase V (EGV) from Humicola insolens, formed by six β-strands with interconnected loops. VpEXPA2 protein contains essential structural moieties related to the catalytic mechanism of EGV, such as the conserved HFD motif. Nevertheless, changes in the catalytic environment are observed in the protein model, influencing its mode of action. The lack of catalytic activity of this expansin and its preference for cellulose are discussed in light of the structural information obtained from the VpEXPA2 protein model, regarding the distance between critical amino acid residues. Finally, the VpEXPA2 model improves our understanding on the mechanism of action of α-expansins on plant cell walls during softening of V. pubescens fruit.

Comparative genomics analysis of Liberibacter species to elucidate pathogenesis and culturability

Liberibacter crescens BT-1, a gram negative, rod-shaped bacterial isolate, was previously recovered from mountain papaya and sequenced. As L. crescens is culturable and is not a pathogen of citrus, comparative genomics of this strain with other uncultured, pathogenic Liberibacter should suggest genes involved in both phenotypes. Genomic comparison to Liberibacter sp. revealed differences in metabolic pathways and virulence genes.  Specific differences in metabolism include the inability of L. asiaticus and L. solanacearum to synthesize histidine, tryptophan, and thiamine, as well as a reduced ability to produce other amino acids. L. asiaticus and L. solanacearum possess a thiamine ABC transporter not found in L. crescens, which may compensate for the inability to synthesize thiamine.  Diversity in the flp pilus operon and metal ABC transporters were observed that may contribute to the pathogenesis of the uncultured species. These differences may contribute to variation in virulence and culturability among species. Finally, two putative prophage regions were found in L. crescens that share moderate functional similarity to the phage regions of L. asiaticus, but sequence similarity is not conserved. Additional genomic comparisons will expand our understanding of virulence and vector-interactions of the described Liberibacter sp.&nbsp

High hydrostatic pressure and ultrasound extractions of antioxidant compounds, sulforaphane and fatty acids from Chilean papaya (Vasconcellea pubescens) seeds: Effects of extraction conditions and methods

This study addressed the use of papaya seeds (Vasconcellea pubescens) as a source of bioactive compounds by using different types of assisted extractions such as high hydrostatic pressure (HHPE), ultrasound (UAE) and conventional (CE) extractions. The results showed that HHPE was more effective than UAE and CE in extracting bioactive compounds and had a shorter extraction time. A high correlation between the antioxidant capacity and total phenolic content indicated that phenolic compounds could be the main source of antioxidant activity in this seed. Fatty acids were identified and quantified; oleic (n-9) and linoleic (n-6) acids were the major acids in papaya seeds. Thus, HHPE and UAE provided effective methods for bio-compound extraction from Chilean papaya seeds and could have potential benefits for the cosmetic, food or pharmaceutical industries.

Liberibacter crescens gen. nov., sp. nov., the first cultured member of the genus Liberibacter.

The Gram-stain-negative, rod-shaped bacterial isolate BT-1(T) is the closest relative to the genus 'Candidatus Liberibacter' cultured to date. BT-1(T) was recovered from the phloem sap of a defoliating mountain papaya in Puerto Rico. The BT-1(T) 16S rRNA gene sequence showed that strain BT-1(T) is most closely related to members of the genus 'Ca. Liberibacter' sharing 94.7% 16S rRNA gene sequence similarity with 'Ca. Liberibacter americanus' and 'Ca. Liberibacter asiaticus'. Additionally, average nucleotide identity, 16S rRNA gene sequences and conserved protein sequences supported inclusion of the previously described species of the genus 'Ca. Liberibacter' in a genus with BT-1(T). The prominent fatty acids of isolate BT-1(T) were C18 : 1ω7c (77.2%), C16 : 0 OH (4.8%), C18 : 0 (4.4%) and C16 : 0 (3.5%). Both physiological and genomic characteristics support the creation of the genus Liberibacter, as well as the novel species Liberibacter crescens gen. nov., sp. nov. with type strain BT-1(T) ( = ATCC BAA-2481(T) = DSM 26877(T)).

The Complete Genome Sequence of ‘Candidatus Liberibacter americanus’, Associated with Citrus Huanglongbing

Liberibacter spp. form a Rhizobiaceae clade of phloem-limited pathogens of limited host range. Two obligately parasitic species have been sequenced: 'Candidatus Liberibacter asiaticus', which causes citrus huanglongbing (HLB) worldwide, and 'Ca. L. solanacearum', which causes potato "zebra chip" disease. A third (proposed) species, Liberibacter crescens, was isolated from mountain papaya, grown in axenic culture, and sequenced. In an effort to identify common host determinants, the complete genomic DNA sequence of a second HLB species, 'Ca. L. americanus' strain 'São Paulo' was determined. The circular genome of 1,195,201 bp had an average 31.12% GC content and 983 predicted protein encoding genes, 800 (81.4%) of which had a predicted function. There were 658 genes common to all sequenced Liberibacter spp. and only 8 genes common to 'Ca. L. americanus' and 'Ca. L. asiaticus' but not found in 'Ca. L. solanacearum'. Surprisingly, most of the lipopolysaccharide biosynthetic genes were missing from the 'Ca. L. americanus' genome, as well as OmpA and a key regulator of flagellin, all indicating a 'Ca. L. americanus' strategy of avoiding production of major pathogen-associated molecular patterns present in 'Ca. L. asiaticus' and 'Ca. L. solanacearum'. As with 'Ca. L. asiaticus', one of two 'Ca. L. americanus' prophages replicated as an excision plasmid and carried potential lysogenic conversion genes that appeared fragmentary or degenerated in 'Ca. L. solanacearum'.

Isolation and Characterisation of PRSV-P Resistance Genes in Carica and Vasconcellea.

Papaya (Carica papaya L.) is one of the major tropical fruit crops worldwide, but it is limited throughout its range by papaya ringspot virus type P (PRSV-P). Previous genetic studies identified a functional PRSV-P resistance marker in a mapping population of F2 plants of Vasconcellea pubescens (resistant to PRSV-P) × Vasconcellea parviflora (susceptible to PRSV-P) and showed that the marker exhibited homology to a serine threonine protein kinase (STK) gene. Full length cDNAs of putative PRSV-P resistance genes designated CP_STK from C. papaya and VP_STK1 and VP_STK2 from V. pubescens were cloned by rapid amplification of cDNA ends (RACE). Due to a frame-shift mutation, the two homologous sequences are transcribed and edited differently such that the gene product in V. pubescens is two separate transcripts, whereas in C. papaya they are fused into a single message. A peroxisomal targeting signal (PTS2) present in VP_STK2 but absent in the other transcripts may be the functional source of PRSV resistance in V. pubescens. The STK gene from V. pubescens may have been derived from an alternative splicing to confer resistance. The putative resistance gene, VP_STK2, that was identified in this study is a potential new source of PRSV-P resistance for papaya genotypes.

Molecular Dynamics Simulation and Site-Directed Mutagenesis of Alcohol Acyltransferase: A Proposed Mechanism of Catalysis

Aroma in Vasconcellea pubescens fruit is determined by esters, which are the products of catalysis by alcohol acyltransferase (VpAAT1). VpAAT1 protein structure displayed the conserved HxxxD motif facing the solvent channel in the center of the structure. To gain insight into the role of these catalytic residues, kinetic and site-directed mutagenesis studies were carried out in VpAAT1 protein. Based on dead-end inhibition studies, the kinetic could be described in terms of a ternary complex mechanism with the H166 residue as the catalytic base. Kinetic results showed the lowest Km value for hexanoyl-CoA. Additionally, the most favorable predicted substrate orientation was observed for hexanoyl-CoA, showing a coincidence between kinetic studies and molecular docking analysis. Substitutions H166A, D170A, D170N, and D170E were evaluated in silico. The solvent channel in all mutant structures was lost, showing large differences with the native structure. Molecular docking and molecular dynamics simulations were able to describe unfavored energies for the interaction of the mutant proteins with different alcohols and acyl-CoAs. Additionally, in vitro site-directed mutagenesis of H166 and D170 in VpAAT1 induced a loss of activity, confirming the functional role of both residues for the activity, H166 being directly involved in catalysis.

Indonesia

Fitriningrum R, Sugiyarto, Susilowati A. 2013. Analysis of carbohydrate content of various maturity levels of Mountain Papaya (Carica pubescens) fruit from Kejajar and Sembungan Villages, Dieng Plateau, Central Java. Bioteknologi 10: 6-14. Mountain papayas (Carica pubescens Lenne & K. Koch) at Dieng Plateau, Central Java were distributed narrowly (+1400 m.asl until +2400 m.asl). Different altitude could determine the climatic environment factors as well as plant metabolism processes. The aim of this research was to compare the carbohydrates content on various maturity levels of mountain papaya fruit from Kejajar and Sembungan Village, Dieng Plateau. Samples of mountain papaya fruit on various maturity levels i.e: upper part, middle part and lower part, were taken from Kejajar Village (+1400 m.asl) and Sembungan Village (+2400 m.asl). Each sample was analyzed it’s rough fibre part, reducing sugar and total of carbohydrate from it’s seed salute and pericarp. The data was analyzed descriptive-comparatively. Result showed that there was tendency more mature of fruit, it’s total carbohydrates content increased, except the total carbohydrate content of pericarp of mountain papaya fruit from Sembungan Village. More mature of mountain papaya fruit, it’s rough fibre part decreased. Highest of reducing sugar was observed on middle fruit. The total carbohydrates content of mountain papaya from Kejajar Village were higher than from Sembungan Village.

Complete genome sequence of Liberibacter crescens BT-1.

Liberibacter crescens BT-1, a Gram-negative, rod-shaped bacterial isolate, was previously recovered from mountain papaya to gain insight on Huanglongbing (HLB) and Zebra Chip (ZC) diseases. The genome of BT-1 was sequenced at the Interdisciplinary Center for Biotechnology Research (ICBR) at the University of Florida. A finished assembly and annotation yielded one chromosome with a length of 1,504,659 bp and a G+C content of 35.4%. Comparison to other species in the Liberibacter genus, L. crescens has many more genes in thiamine and essential amino acid biosynthesis. This likely explains why L. crescens BT-1 is culturable while the known Liberibacter strains have not yet been cultured. Similar to Candidatus L. asiaticus psy62, the L. crescens BT-1 genome contains two prophage regions.

Molecular docking simulation analysis of alcohol acyltransferases from two related fruit species explains their different substrate selectivities

Tropical papaya (Carica papaya) and mountain papaya (Vasconcellea pubescens) fruits are characterised for their strong and particular aroma. The aroma of both fruits is different and dominated by esters, which are synthesised by alcohol acyltransferases (AATs). The ability to produce esters is contrasting, V. pubescens (VpAAT1) being a very active enzyme towards the production of benzyl acetate, whereas C. papaya (CpAAT1) is more active towards the production of ethyl butanoate and methyl butanoate, but not benzyl acetate. In order to understand the mechanism of action at the molecular level, the structural model of CpAAT1 protein was built by comparative modelling. Conformational interaction between the protein and several ligands was carried out by molecular docking. CpAAT1 structure showed two domains connected by a large crossover loop, with a solvent channel in the centre of the structure. CpAAT1 and VpAAT1 proteins showed similar 3D structures, including their catalytic sites, but their solvent channels showed differences in size and shape. CpAAT1 solvent channel is larger, in agreement with its higher selectivity for large acyl-CoA substrates. In addition, the most favourably predicted substrate orientation in CpAAT1 was observed for methanol and butanoyl-CoA, showing a perfect coincidence with the high production rate of methyl butanoate of C. papaya fruit.

GENE FOR PRSV-P RESISTANCE IN VASCONCELLEA SPECIES AND DEVELOPMENT OF PRSV-P RESISTANT PAPAYA VIA INTERGENERIC HYBRIDISATION

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Genomics and Genetic Transformation of Horticultural Crops GENE FOR PRSV-P RESISTANCE IN VASCONCELLEA SPECIES AND DEVELOPMENT OF PRSV-P RESISTANT PAPAYA VIA INTERGENERIC HYBRIDISATION

Rehydration Capacity of Chilean Papaya (Vasconcellea pubescens): Effect of Process Temperature on Kinetic Parameters and Functional Properties

Slabs of Chilean papaya hot air-dried at 60 °C were rehydrated at 20, 40, 60, and 80 °C to study the influence of process temperature on mass transfer kinetics during rehydration. Diffusive and empirical models were selected to simulate the experimental rehydration curves. All models parameters showed dependence with temperature, thus activation energy could be estimated according to an Arrhenius-type equation. Among the applied models, Weibull provided the best fit for each rehydration curve based on the statistical tests RMSE, SSE, and chi-square. According to these results, this model could be used to estimate the rehydration time of Chilean papaya. In addition, rehydration ratio and water-holding capacity were analyzed. Both indices showed a decrease with increasing rehydration temperature indicating modification of the papaya cell structure due to thermal treatment which resulted in a reduction of the rehydration ability, in particular at high rehydration temperatures.