Antonio Cano

Physiological changes in peaches related to chilling injury and ripening

Abstract Firm-breaker (FB) and firm-mature (FM) peaches cv. ‘Paraguayo’ were either stored for 4 weeks at 2°C or subjected to three cycles of 1 day of intermittent warming (IW) at 20°C every 6 days at 2°C. Normal postharvest ripening and post-storage ripening at 20°C were also studied in order to relate postharvest physiology with the onset of chilling injuries (CI) (woolliness, gel breakdown and scald). As far as we know, both gel breakdown and scald have been described and reported on peaches for the first time. FB peaches were more sensitive to CI than FM ones. A high respiration rate and ethylene production in conventionally stored fruit after 2 weeks of storage, followed by a drop in ethylene production, was accompanied by the development of CI in fruit of both maturity stages. IW strongly reduced CI during storage. Periodic warming acclimatised chilled fruit to subsequent periods of chilling by allowing them to ripen due to the production of a suitable amount of ethylene, depending on their maturity stage at harvest. The increase in ethylene production during post-storage ripening could be related to the development of over-ripeness.

Physiological responses of tomato fruit to cyclic intermittent temperature regimes

Long life tomatoes (Lycopersicon esculentum Mill. cultivar ‘Durinta’) at breaker stage, treated with 0.5 g l 1 iprodione or washed in water, were stored at 9, 12 or 20°C for up to 28 days. Fruit stored at 9°C were warmed to 20°C for 1 day every week, whereas fruit stored at 12°C were cooled to 2°C for 1 day every week. Fungicide treatment reduced decay and pitting on fruit stored more than 3 weeks. At 9°C, a slight synergistic effect on fruit pitting was observed from fungicide alone or fungicide plus intermittent warming. Compared with fruit stored at a constant 9°C, intermittently warmed tomatoes had better surface colour and flavour, were slightly less firm with less severe pitting, and were in better condition both at the end of the storage period and after a 3-day shelf-life. In fruit held at constant 20°C, 9°C or intermittently warmed, increased pectolytic enzyme activity accompanied a fall in respiration rate and ethylene production. In fruit held at a continuous 9°C, polygalacturonase activity was reduced slightly during the third week of storage. Intermittently cooled fruit showed enhanced taste and appearance compared with fruit held at a constant 12°C, but had more decay and pitting after the second cooling treatment. After cooling, slight reductions in L*a*b* Colour Space lightness were detected. During the shelf-life period, tomatoes previously stored continuously for 2 or 3 weeks at 9 or 12°C produced more ethylene and had higher respiration rates. By the third week, ethylene production was severely reduced by cooling at 2°C, but a possible relationship between pitting and non-ripening-dependent ethylene production was indicated. The respiration rate was not affected by the disorder incidence. We conclude that intermittent warming is more beneficial than intermittent cooling because of pitting development at 2°C in intermittently cooled fruit.

Influence of rootstock and cultivar on bioactive compounds in citrus peels

BACKGROUND Citrus fruits have a beneficial effect on human health because of their nutritional and antioxidant properties, and their consumption is associated with a decrease in the incidence of cardiovascular disease and reduced risk of certain cancers. Seven cultivars of mandarin and orange species from the Mediterranean area, grafted onto different rootstocks (Cleopatra mandarin and Troyer citrange), have been analysed. The influence of the rootstock on the content of bioactive compounds is discussed. RESULTS In all citrus cultivars and rootstocks studied, hesperidin and narirutin flavonoids were the main flavanone glycosides identified, β-cryptoxanthin and violaxanthin the most abundant carotenoids, limonene was the most abundant essential oil, calcium and potassium were the dominant macronutrients and, among the micronutrients, iron and boron represented the highest proportions. CONCLUSION We have been found clear differences in the content of bioactive compounds for the different groups, in agreement with the Citrus classification. Although both mandarin and orange varieties showed similar tendencies concerning the majority of bioactive constituents, the proportion of the individual nutrients ranged among different cultivars and our results indicated differences between rootstocks although it would be necessary to carry out more analyses, and with the new rootstocks obtained from different breeding programmes, to elucidate conclusive values.

Interactions among cooling, fungicide and postharvest ripening temperature on peaches

Abstract Peach fruit (Prunus persica L. cv. ‘Miraflores’) harvested at the firm-ripe stage, treated or not with 2 g l−1 iprodione, were cooled or not at 1°C and ripened at 15 or 20°C and 95% RH for 10 days. During ripening, weight loss, fungal development and changes in quality parameters (firmness, soluble solids content, titratable acidity, pH and ground and flesh color), and carbon dioxide and ethylene production were monitored. Cooling alone or combined with iprodione avoided Rhizopus nigricans decay during ripening at either ripening temperatures. A skin damage not previously reported on fungicide treated peach was observed at 20°C. Cooled fruit ripened at 15°C showed an anomalous respiration rate and ethylene production after the climacteric peak, a loss of firmness and a drop in titratable acidity after 7 days of storage, and reduced endo-polygalacturonase activity in presence of continuous pectinmethylesterase activity during the first week. Cooling before ripening at 20°C led to the best flavor without excessive total losses. These results helped in the optimization of warming cycles during cold storage used to avoid chilling injuries development on peaches.

Inhibition of etiolated lupin hypocotyl growth and rooting by peroxides, ascorbate and glutathione

Summary The influence of two oxidants. (H 2 0 2 and m-chloroperoxibenzoic acid. (mCPBA)) and two reductants. (ascorbate. (ASC) and glutathione. (GSH)) on growth and rooting of the etiolated Lupinus albus L. hypocotyls has been studied. Lupin seedlings were derooted and the hypocotyls treated for 24 h with aqueous solutions containing different concentrations. (from 10 µM to 50 mM) of the above compounds. The hypocotyl length and the number and length of the adventitious roots were determined periodically. All the assayed compounds showed a capacity to inhibit growth and rooting of the hypocotyls, the effect being dependent on the compound and its concentration. As a rule, the greater the concentration, the higher the inhibition. The compounds can be classified from higher to lower efficiency as inhibitors as follows: mCPBA, GSH, ASC and H 2 O 2 ; therefore, inhibitory efficiency is seemingly dependent on the compound per se rather than on its redox nature. The higher effectiveness as inhibitor of mCPBA and GSH is discussed in light of their capacity to inactivate enzymes such as peroxidases, which are involved in plant development and in the protective mechanism against oxidative stress. The fact that younger, actively growing tissues were less sensitive than older hypocotyl tissues to the toxicity of mCPBA and GSH supports the view of a changing endogenous redox state during growth. Data presented here suggest that regulation of the redox balance is decisive in regulating plant morphogenesis.

Influence of peroxides, ascorbate and glutathione on germination and growth in Lupinus albus L.

Lupinus albus L. seeds were treated with different concentrations (from 10 µM to 50 mM) of H2O2, m-chloroperoxybenzoic acid (mCPBA), ascorbate (ASC) and glutathione (GSH). The efficiency as inhibitors on germination and on the subsequent growth of the hypocotyl was mCPBA > GSH > ASC = H2O2, which suggest that inhibitory efficiency was dependent on the compound per se rather than on its redox nature.