RESUMO
Excessive softening is a major cause of postharvest deterioration during transportation and storage of fresh cherries. In continuing our studies to identify the factors determining the textural differences between sweet cherry fruit genotypes, we evaluated the solubilization, depolymerization, and monosaccharide composition of pectin and hemicelluloses from five sweet cherry cultivars ('Chelan', 'Sumele', 'Brooks', 'Sunburst', and 'Regina') with contrasting firmness and cracking susceptibility at two developmental stages (immature and ripe). In contrast to what is usually shown in most fruits, cherry softening could occur is some cultivars without marked increases in water-soluble pectin. Although polyuronide and hemicellulose depolymerization was observed in the water-soluble and dilute-alkali-soluble fractions, only moderate association occurs between initial polymer size and cultivar firmness. In all the genotypes the Na2CO3-soluble polysaccharides (NSF) represented the most abundant and dynamic wall fraction during ripening. Firm cultivars showed upon ripening a lower neutral sugars/uronic acid ratio in the NSF, suggesting that they have a lower proportion of highly branched polyuronides. The similar molar ratios of arabinose plus galactose to rhamnose [(Ara+Gal)/Rha] suggest that the cultivars differed in their relative proportion of homogalacturonan (HG) and rhamnogalacturonan I (RG-I) rather than in the size of the RG side chains; with greater proportions of HG in firmer cherries. Ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was useful to identify the depolymerization patterns of weakly bound pectins, but gave less accurate results on ionically bound pectins, and was unable to find any pattern on covalently bound pectins.
Assuntos
Parede Celular/química , Polissacarídeos/química , Prunus/química , Parede Celular/metabolismo , Frutas/química , Frutas/crescimento & desenvolvimento , Frutas/metabolismo , Polissacarídeos/metabolismo , Prunus/classificação , Prunus/crescimento & desenvolvimento , Prunus/metabolismoRESUMO
Non-chilling peel pitting (NCPP), a storage disorder resulting in the formation of depressed areas in the peel of many citrus cultivars, is reduced by ethylene treatments. We hypothesized that this effect may be associated with biochemical changes of cell wall components. Therefore, we extracted cell wall material from albedo and flavedo tissues of 'Navelate' oranges stored in air, conditioned with ethylene (2µLL(-1)) for 4 days and subsequently transferred to air, or continuously stored in an ethylene-enriched atmosphere (2µLL(-1)). Uronic acids and neutral sugars were extracted into five fractions enriched in specific wall polymers namely water-, CDTA-, Na2CO3-, and 1 and 4M KOH-soluble fractions. Pectin insolubilization was found in control fruit at long storage times. Ethylene treatments, alleviating NCPP, increased polyuronide solubility in the albedo and had a slight effect on the flavedo. Ethylene-treated fruit showed greater content of water-soluble neutral sugars and a larger proportion of hemicelluloses readily extractable with 1M KOH, with a concomitant reduction in the 4M KOH-soluble fraction. This suggests that the protective role of ethylene on NCPP is associated with an increased solubilization of the wall of albedo cells.
Assuntos
Parede Celular/efeitos dos fármacos , Citrus sinensis/efeitos dos fármacos , Etilenos/farmacologia , Frutas/efeitos dos fármacos , Pectinas/metabolismo , Metabolismo dos Carboidratos , Carboidratos , Parede Celular/metabolismo , Celulose/metabolismo , Citrus sinensis/fisiologia , Temperatura Baixa , Frutas/fisiologia , Polissacarídeos/metabolismo , Solubilidade , Ácidos Urônicos/análise , Ácidos Urônicos/metabolismoRESUMO
UNLABELLED: The objective of this work was to select a Ultraviolet-C (UV-C) treatment for fresh-cut mature green bell pepper, and to evaluate the effect of its combination with refrigeration on quality maintenance. Bell pepper sticks were treated with 0, 3, 10, or 20 kJ/m² UV-C in the outer (O), inner (I), or both sides of the pericarp (I/O) and stored for 8 d at 10 °C. During the first 5 d of storage, all UV-C treatments reduced deterioration as compared to the control. The treatment with 20 kJ/m² I/O was the most effective to reduce deterioration, and was used for further evaluations. In a second group of experiments, mature green bell pepper sticks were treated with 20 kJ/m² I/O, stored at 5 °C for 7 or 12 d and assessed for physical and chemical analysis, and microbiological quality. UV-C-treated fruit showed lower exudates and shriveling than the control. UV exposure also reduced decay, tissue damage, and electrolyte leakage. After 12 d at 5 °C, UV-C irradiated peppers remained firmer and had higher resistance to deformation than the control. The UV-C treatments also reduced weight loss and pectin solubilization. UV-C exposure decreased the counts of mesophile bacteria and molds, and did not affect acidity or sugars. UV-C-treated fruit stored for 0 or 7 d at 5 °C did not show major differences in antioxidants from the control as measured against DPPH(â¢) or ABTS(â¢)⺠radicals. Results suggest that UV-C exposure is useful to maintain quality of refrigerated fresh-cut green pepper. PRACTICAL APPLICATION: Exposure to UV-C radiation before packing and refrigeration could be a useful nonchemical alternative to maintain quality and reduce postharvest losses in the fresh-cut industry.
Assuntos
Capsicum/efeitos da radiação , Fast Foods/efeitos da radiação , Irradiação de Alimentos/métodos , Embalagem de Alimentos , Armazenamento de Alimentos , Frutas/efeitos da radiação , Raios Ultravioleta , Antioxidantes/análise , Capsicum/crescimento & desenvolvimento , Capsicum/microbiologia , Fenômenos Químicos , Carboidratos da Dieta/análise , Relação Dose-Resposta à Radiação , Eletrólitos/análise , Fast Foods/análise , Fast Foods/microbiologia , Frutas/crescimento & desenvolvimento , Frutas/microbiologia , Fungos/crescimento & desenvolvimento , Fungos/efeitos da radiação , Bactérias Gram-Negativas/crescimento & desenvolvimento , Bactérias Gram-Negativas/efeitos da radiação , Bactérias Gram-Positivas/crescimento & desenvolvimento , Bactérias Gram-Positivas/efeitos da radiação , Concentração de Íons de Hidrogênio , Fenômenos Mecânicos , Pectinas/análise , Pectinas/química , Controle de Qualidade , SolubilidadeRESUMO
Preharvest conditions can have a great impact on fruit quality attributes and postharvest responses. Firmness is an important quality attribute in pear, and excessive softening increases susceptibility to bruising and decay, thus limiting fruit postharvest life. Textural characteristics of fruits are determined at least in part by cell wall structure and disassembly. Few studies have analyzed the influence of fruit preharvest environment in softening, cell wall composition, and degradation. In the current work 'Bartlett' pears grown either facing the sun (S) or in the shade (H) were harvested and stored for 13 days at 20 °C. An evaluation of fruit soluble solids, acidity, color, starch degradation, firmness, cell wall yield, pectin and matrix glycan solubilization, depolymerization, and monosaccharide composition was carried out. Sun-exposed pears showed more advanced color development and similar levels of starch degradation, sugars, and acids than shaded fruit. Sunlight-grown pears were at harvest firmer than shade-grown pears. Both fruit groups softened during storage at 20 °C, but even after ripening, sun-exposed pears remained firmer. Sunlight exposure did not have a great impact on pectin molecular weight. Instead, at harvest a higher proportion of water-solubilized uronic acids and alkali-solubilized neutral sugars and a larger mean molecular size of tightly bound glycans was found in sun-exposed pears. During ripening cell wall catabolism took place in both sun- and shade-grown pears, but pectin solubilization was clearly delayed in sun-exposed fruit. This was associated with decreased removal of RG I-arabinan side chains rather than with reduced depolymerization.
Assuntos
Parede Celular/química , Polissacarídeos/química , Polissacarídeos/metabolismo , Pyrus/metabolismo , Pyrus/efeitos da radiação , Parede Celular/metabolismo , Pyrus/química , Pyrus/crescimento & desenvolvimento , Luz SolarRESUMO
We evaluated the effect of short-term gaseous ozone treatment (10 microL/L; 10 min) on tomato fruit quality and cell wall degradation. The treatments did not modify fruit color, sugar content, acidity, or antioxidant capacity but reduced fruit damage and weight loss and induced the accumulation of phenolic compounds. In addition, softening was delayed in ozone-treated fruit. Cell wall analysis showed that exposure to ozone decreased pectin but not hemicellulose solubilization. Polyuronide depolymerization was also reduced in ozone-treated fruit. While the treatments did not alter the activity of the pectin-degrading enzymes polygalacturonase (PG) and beta-Galactosidase (beta-Gal), a clear decrease in pectin methyl esterase (PME) was found. Results show that short-term ozone treatments might be useful to reduce fruit damage and excessive softening, two of the main factors limiting tomato postharvest life, without negatively affecting other quality attributes. The impact of the treatments on fruit softening might be associated with reduced disassembly (solubilization and depolymerization) of pectic polysaccharides.