Influences of convective and vacuum drying on the quality attributes of osmo-dried pequi (Caryocar brasiliense Camb.) slices
Introduction
Pequi (Caryocar brasiliense Camb.) is a typical fruit from Brazilian Cerrado. It has high nutritional value, being very rich in bioactive compounds with antioxidant properties, such as carotenoids and ascorbic acid (Machado, Mello, & Hubinger, 2013). Dietary intake of these molecules has gained attention because they are associated with reduced risk of developing chronic diseases, such as cardiovascular diseases, cancer, cataract and macular degeneration (Neto, 2007). Currently, pequi is consumed in the region fresh or as an ingredient (Geoze et al., 2013). Its consumption abroad, or even in other parts of Brazil, is limited by the lack of appropriate preservation methods (Machado et al., 2013).
Drying is a traditional process for extending the shelf life of foods (Corrêa, Viana, Mendonça, & Justus, 2016). Dried pequi slices could be used as an ingredient in domestic and industrial preparations, and used to enrich foods with bioactive compounds. Thus, the production of dried pequi slices might increase the economic value of the fruit, expand its consumer market and develop its agribusiness potential. However, the drying process should be examined closely taking into account the degradation of bioactive compounds, quality as related to oxidative damage, loss of flavor, browning, and shrinkage (Orikasa et al., 2014).
Ascorbic acid and carotenoids are thermosensitive compounds that are easily oxidized during drying under normal atmospheric conditions (Demiray et al., 2013, Gümüşay et al., 2015, Santos and Silva, 2008). Using low temperatures and reducing exposure to oxygen when drying carrots can minimize oxidization, degradation of carotenoids and ascorbic acid, and improve the capacity for rehydration as well as retaining the color (Liu, Wu, & Miao, 2014).
Osmotic dehydration (OD) is used as a pretreatment to partially remove water (Corrêa, Ernesto, & Mendonça, 2016) in combination with drying process (Junqueira, Corrêa, & Mendonça, in press). OD could improve the drying rate in a subsequent process, help inhibit enzymatic browning, retain natural color (Corrêa, Dev, Gariepy, & Raghavan, 2011), limit the structural collapse and shrinkage, hardening and poor appearance (Oikonomopoulou & Krokida, 2013) and improve the sensory, functional and even nutritional properties of dried products.
The aims of this work were to (i) investigate the effect of osmotic dehydration on pequi slices at different solution concentrations, (ii) examine the influence of osmotic pretreatment, drying temperature and vacuum use during drying on the quality of dried pequi slices and (iii) to find out suitable treatments for producing high quality dried pequi slices.
Section snippets
Sample preparation
Pequi fruits (Caryocar brasiliense Camb.) were obtained from the Cerrado region in the north of Minas Gerais state (Brazil) during the harvest period (January 2013). The fruits were stored at 4 °C (±2 °C) until selection, which was usually within a week. Undamaged ripe fruits were selected by size and uniformity. After selection, they were washed in tap water and sanitized with sodium hypochlorite solution (Corrêa et al., 2014, Viana et al., 2014). The external mesocarp was removed manually with
Characterization
The physical and chemical characteristics of fresh pequi pulp are presented in Table 2. The characteristics of fresh samples were similar to those published previously (Lima et al., 2007, Oliveira et al., 2010, Santana et al., 2013).
Osmotic dehydration
The moisture content (X), water activity (aw), and ascorbic acid (AsA) and carotenoid contents (CC) of the osmotically dehydrated samples are presented in Table 2. The osmotically treated samples had significantly lower X, aw, AsA and CC compared with the fresh
Conclusion
Increased sucrose concentration intensified mass transfer between the solution and the food during osmotic dehydration. It also limited shrinkage in subsequent drying. However, lower sucrose concentrations preserved pequi bioactive compounds in the final product. Osmotic dehydration and longer drying periods were associated with a reduction in bioactive compound content, and thus not recommended for sliced pequi. Vacuum drying at lower temperatures is recommended for preparing dried sliced
Acknowledgements
The authors want to thank the Research Support Foundation of Minas Gerais (FAPEMIG), Coordination for the Improvement of Higher Education Personnel (CAPES) and the National Council of Technological and Scientific Development (CNPq) for financial support.
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