Effects of relative humidity and temperature on small scale peach fruit drying using a tunnel solar dryer: a case study of peach fruit produced by small scale farmers in the midlands of Kwazulu-Natal, South Africa

The study investigated the relationships between tunnel and ambient temperature and relative humidity (RH) and their effects on the performance of a tunnel solar dryer tested by drying peach slices. The temperature and RH showed an inverse proportion because if the ambient temperature increased, both the tunnel and ambient RH dropped. There was a direct proportion between the increasing ambient temperature and increased tunnel temperature. The use of treatment such as ascorbic acid or lemon juice did not have a significant effect on the overall drying between the yellow and white landraces. Ascorbic acid had a tendency to perform better than lemon juice which was also better than the untreated slices in terms of the taste and overall acceptability of the dried products. White peach slices were of better quality than yellow slices. It was concluded that solar drying is possible in the Midlands region. Extension officers and researchers can work hand in hand in partnerships with communities in implementing old and cheap but ignored technologies such as this method of food drying.Keywords: Ambient temperature, ambient RH, tunnel RH, tunnel temperature, lemon juice, ascorbic aci

Diversity for chemical composition in a collection of different varietal types of tree tomato (Solanum betaceum Cav.), an Andean exotic fruit

[EN] We evaluated 23 tree tomato (Solanum betaceum) accessions from five cultivar groups and one wild relative (Solanum cajanumense) for 26 composition traits. For all traits we found highly significant differences (P < 0.001) among the materials studied. The high diversity found within S. betaceum for composition traits was matched by a high diversity within each of the cultivar groups. We found that sucrose and citric acid were the most important soluble sugar and organic acid, respectively, in tree tomato. Fruit in the anthocyanin pigmented (purple) group had a carotenoid content similar to that in the yellow-orange cultivar groups. Total phenolic content was significantly correlated (r = 0.8607) with antioxidant activity. Analyses of mineral content showed that tree tomato is a good source of K, Mg, and Cu. Multivariate principal components analysis (PCA) confirmed that an important diversity exists within each cultivar group. The results we have obtained indicate that the high diversity found within the tree tomato could be exploited for selection and breeding for developing the tree tomato as a commercial crop. (C) 2014 Elsevier Ltd. All rights reserved.This work was partially financed by the Ecuadorian Secretaria Nacional de Educacion Superior, Ciencia, Tecnologia e Innovacion from Ecuador (SENESCYT).Acosta-Quezada, P.; Raigón Jiménez, MD.; Riofrío-Cuenca, T.; García Martínez, MD.; Plazas Ávila, MDLO.; Burneo, J.; Figueroa, JG.... (2015). Diversity for chemical composition in a collection of different varietal types of tree tomato (Solanum betaceum Cav.), an Andean exotic fruit. Food Chemistry. 169:327-335. doi:10.1016/j.foodchem.2014.07.152S32733516

Conservação de café torrado e moído durante o armazenamento. Parte 2: Massa específica e porosidade

The determination of physical properties is an important factor in the design of machinery and the scaling of post-harvest operations. The present study evaluates the influence of the level of roasting and the size of grinding on the physical properties of coffee during storage. The following physical properties were evaluated: true and bulk density, and intergranular porosity. Raw coffee beans (Coffea canephora and Coffea arabica), hulled and dried, were roasted to two different levels: medium light (SCAA#65) and moderately dark (SCAA#45). The beans were then grinded into three different sizes: fine (0.59 mm), medium (0.84 mm) and coarse (1.19 mm). An additional coffee lot was kept whole. Following grinding, samples were stored at two different temperatures (10 and 30 ºC) and analyzed after five different storage durations (0, 30, 60, 120 and 180 days). The medium light roast had higher values for each of the measured physical properties. Finely ground samples had higher true and bulk densities, and porosities. It is concluded that the size of grinding, level of roasting and duration of storage significantly affect the physical properties of coffee.A determinação das propriedades físicas é fator importante na formulação de projetos de maquinários e dimensionamento de operações pós-colheita. De forma a permitir o dimensionamento correto e o uso desses maquinários, objetivou-se avaliar e determinar, durante o armazenamento, as propriedades físicas: massa específica unitária e aparente e porosidade intergranular, além de avaliar a influência dos níveis de torrefação e moagem sobre essas propriedades. Grãos de café cru (Coffea canephora e Coffea arabica) foram utilizados, descascados e secados e só então torrados em dois níveis: média clara (SCAA#65) e moderadamente escura (SCAA#45). Os grãos foram moídos em três granulometrias: fina (0,59 mm), média (0,84 mm) e grossa (1,19 mm), além do lote de café inteiro. Realizada a moagem as amostras foram armazenadas em duas temperaturas (10 e 30 ºC) e analisadas em cinco tempos distintos de armazenamento (0, 30, 60, 120 e 180 dias). A torra média clara permitiu maiores valores das propriedades físicas; já as amostras de granulometria fina apresentaram aumento das massas específica unitária e aparente e porosidade. Conclui-se que a granulometria, o nível de torrefação e o tempo de armazenamento, afetaram as propriedades físicas do café.National Council for Scientificand Technological Development/[CNPq nº 14/2012]/CNPq/BrasilUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro para Investigaciones en Granos y Semillas (CIGRAS

Mathematical modeling of convective air drying of quinoa-supplemented feed for laboratory rats

Drying kinetics of quinoa-supplemented feed for laboratory rats during processing at 50, 60, 70, 80 and 90ºC was studied and modeled in this work. Desorption isotherm was obtained at 60ºC giving a monolayer moisture content of 0.04 g water/g d.m. The experimental drying curves showed that drying process took place only in the falling rate period. Several thin-layer drying equations available in the literature were evaluated based on determination coefficient (r²), sum squared errors (SSE) and Chi-square (&#967;2) statisticals. In comparison to the experimental moisture values, the values estimated with the Logarithmic model gave the best fit quality (r² >0.994, SSE < 0.00015 and &#967;2 < 0.00018), showing this equation could predict very accurately the drying time of rat feed under the operative conditions applied

Determinations of physical and chemical properties of KwaZulu-Natal’s household white peach ‘landrace’ in relation to extension services - a case study of Impendle Local Municipality

Indigenous fruits constitute a very important part in the food basket of the household farming community in South Africa. Household growers of white peach landrace in KwaZulu-Natal at Impendle Local Municipality suffer major losses due to lack of maturity indices that would allow them to predict and plan for harvesting dates. As a result, the fruit is harvested later than its physiologically correct date and processing becomes difficult when the fruit is overripe or spoilt. Extension services do not have enough information on such fruit quality parameters to assist the farmers. With the aim of developing and promoting the value chain in household farming, this study identified physical and chemical parameters linked to peach landrace maturity in relation to extension. Maturity and ripening related parameters were determined. Fruit reached maturity 129 days after full bloom (DAFB) and this coincided with mass, volume and moisture content at respective stages of 80.00 g, 55.20 cm3, and 83%. Firmness decreased significantly from 79.00 N to 24.70 N during ripening. Total soluble solids (TSS) increased from 13.5 to 19.00 °Brix. The pH value decreased from 3.40 to 4.00. The TSS:TA (titrable acidity-TA) ratio increased from 21.11 to 35.84. The results showed that DAFB, firmness, mass, TSS, volume, and TSS:TA ratio have potential to be used in relation to extension for maturity indexing of white landrace peach fruit as parameters to determine the maturity indices and quality of the smallholder farmer.Keywords: Extension services, Local informal market, Degree of ripeness, Postharvest quality, Maturit

Convective, vacuum and microwave drying kinetics of mallow leaves and comparison of color and ascorbic acid values of three drying methods

Mallow leaves (Malva sylvestris L.) with initial moisture of 5.02±0.003 on dry basis (82.5% on wet basis) were dried using three different drying methods, microwave, convective and vacuum. The leaves that weigh 75 g each were dried until their moisture fell down to 0.10±0.005 on dry basis (approximately 9% on wet basis). The following drying levels were used in each of the drying processes: 6.67, 8.67, 10, 11.33 W g-1 microwave power density; 50, 75, 100 and 125 °C for convective drying; and 3, 7 kPa at 50 and 75 °C for vacuum drying. Drying periods ranged from 6-10, 26-150 and 38-130 min. for microwave, convective and vacuum drying, respectively. Effective moisture diffisuvities ranged from 2.04403 10-10-3.63996 10-12 m2 s-1, 1.70182 10-11-1.10084 10-10 m2 s-1 and 1.85599 10-11-5.94559 10-10 m2 s-1 for microwave, convective and vacuum drying, respectively. According to ascorbic acid content and color parameters, the best microwave power density was found 10 W g-1 with a drying period of 6.5 min