Effcet of ripening stage on the solar drying kinetics and properties of S. Bartolomeu pears (Pirus Communis L.) (original) (raw)

Solar drying kinetics of pears harvested at different ripening stages

2009

In Portugal, pears of the variety S. Bartolomeu have been used to produce a traditional product named "pêra passa de Viseu". These pears are dried at direct open air sun exposure, following a multi-step procedure. In the last years some investigation around this product and the production method has been carried out to better understand them and establish alternative production techniques. In the present work pears of the variety S. Bartolomeu, harvested at three different moments, corresponding to three ripening stages, were dried in a solar stove and their drying kinetics were studied. From the results obtained it was possible to conclude that all the six equations used to model the drying kinetics fit with accuracy the experimental data, and that the differences found in the three essays result mainly from the climatic conditions that occurred in each drying period.

Properties of pears harvested at different ripening stages

2009

Pears of the variety S. Bartolomeu have been used over the years in Portugal to produce a traditional dried pear known as "pera passa". The processing comprehends a solar drying performed at open air, with obvious disadvantages, either concerning the drying efficiency or the sanitary quality of the final product, taking into account that the products are exposed to multiple contamination agents. For these reasons, attempts have been made to study alternative production methodologies, including the use of solar stoves, among others. In the present work pears of the variety S. Bartolomeu which were harvested at three different moments, and therefore correspond to three different ripening stages, were dried in a solar stove and the evolution of some properties was monitored along the drying process. From the results obtained was possible to conclude that the pears harvested in the two first dates show quite similar trends through drying, while the pears harvested at the last date reveal a clear distinct behavior, allowing to infer that the ripening stage at harvest plays an important role in the subsequent drying operation.

Study of the drying kinetics of solar-dried pears

Biosystems Engineering, 2007

In this study, the drying rates of solar-dried pears were investigated for fruits of the varieties Amêndoa, Amorim, Carapinheira Branca and S. Bartolomeu, all originating from Portugal. From the results it was possible to conclude that the varieties showed a similar drying behaviour, characterised by the absence of the constant drying-rate period and by a falling-rate period involving two different stages, according to the degree of moisture removal. The experimental data for the variations in water content over time was fitted to two different empirical models with the better performance coming from the sigmoid function. The data for the curves of drying rate versus moisture content were fitted to one model, with good results. The variations of the drying rate with time were fitted to two models with the first-order kinetic function fitting the experimental data better than a seconddegree polynomial. The experimental data were used to predict effective diffusivity according to Fick's law with the values of diffusivity obtained ranging from 9.756eÀ10 m 2 s À1 for the variety S. Bartolomeu to 1.160eÀ9 m 2 s À1 for pears of the variety Amorim.

Drying kinetics of prickly pear fruit (Opuntia ficus indica)

Journal of Food Engineering, 2004

The present work examines the effect of drying air conditions on drying kinetics of the prickly pear fruit in a convective solar drier operating with an auxiliary heating system under air controlled conditions. Moreover, the prickly pear fruits are sufficiently dried in the ranges between 32 and 36°C of ambient air temperature, 50-60°C of drying air temperature, 23-34% of relative humidity, 0.0277-0.0833 m 3 /s of drying air flow rate and 200-950 W/m 2 of solar radiation. The results verified with good reproducibility that drying air temperature is the main factor in controlling the drying rate and the experimental drying curves show only a falling rate period. The expression of the drying rate equation is determined empirically from the characteristic drying curve. Eight different thin layer drying models were compared according to their coefficients of determination to estimate solar drying curves. The two-term model was found to satisfactorily describe the solar drying curves of prickly pear fruit with a correlation coefficient (r) of 0.9999. The constants and coefficients of this model could be explained by the effect of drying air temperature with a correlation coefficient (r) of 1.0000.