Electron beam irradiation of sun-dried apricots for quality maintenance
Introduction
Apricot (Prunus armeniaca L.) belongs to the climacteric class of fruits and has become a product of interest in recent years because of its nutritional and health benefits. Apricot is a rich source of β-carotene, ascorbic acid, iron, potassium, fiber, and sugar, which are essential for normal growth and development (Doymaz, 2004, Hussain et al., 2011, Jiménez et al., 2008). Fresh apricots have a short shelf-life partly ascribed to a high respiration rate and a rapid ripening process. These fruits are also sensitive to microbial spoilage even at storage conditions of low temperature and high relative humidity (Sharma et al., 1992, Egea et al., 2007). Therefore, improved methods for apricots preservation should be developed.
To date, the most conventional method for apricot preservation is open-air sun drying because it reduces the moisture content of apricots to extend shelf life. However, this method is time consuming and requires that apricots be exposed to open environment, in which dried apricots easily become contaminated by dust and microorganisms. Consequently, the fruits decompose during transportation and storage and thus become unhygienic and low quality (Vagenas and Marinos-Kouris, 1991, Kostaropoulos and Saravacos, 1995). To solve the problem, apricots are commonly treated with sulfur dioxide before sun drying because sulfur dioxide provides antimicrobial protection at low concentrations and retards both enzymatic and non-enzymatic browning reactions during drying and storage. Therefore, the shelf life of apricot is extended and its natural reddish-yellow color is well maintained (Elmaci et al., 2008). However, low concentrations of sulfur dioxide can cause bronchoconstriction in patients with asthma, whereas higher concentrations may exert the same effect even in healthy individuals. As a result, some countries have established regulations restricting the use of sulfur dioxide in dried products (Cetinkaya et al., 2006). To overcome these adverse effects of chemical preservatives as fumigants, alternative processes are needed.
Irradiation of food products by ionizing radiation can control microorganisms and enhance shelf life with minimum effects on functional, nutritional, and sensory properties. Irradiation is widely recognized as an alternative to chemical preservatives for treating fresh and dried agricultural products worldwide (Hong et al., 2008, Teets et al., 2008, Zhao et al., 2012). Previous investigations have revealed that medium doses (2.5–3.0 kGy) of gamma irradiation is an effective post-harvest treatment in terms of good quality maintenance and quarantine control of sun-dried apricots (Hussain et al., 2011). By contrast, electron beams (EBs) have superior dose rates than gamma rays, produce no nuclear waste, and are low cost (Lewis et al., 2002; Moreno et al., 2007b). However, to the best of our knowledge, reports on the effect of EB irradiation on the quality of sun-dried apricots are limited.
This study aimed to evaluate the effect of EB treatment on the chemical, sensory, and microbial quality of unsulfured sun-dried apricots during storage, as well as to determine the optimum radiation levels at which fruit quality can be well maintained.
Section snippets
Apricots
Fresh “xiaobai” apricots were harvested in the commercial ripening stage in Xinjiang Province, China. The apricots, after selection of size and color, were direct sun dried under open conditions (temperature 20–40 °C, relatively humidity 25–50%) without sulfur dioxide pretreatment in summer. Drying was completed within 16–20 days. The sun-dried apricots were then packed in polyethylene packs (1 kg of apricots each), sealed, and irradiated with EB.
EB irradiation treatment
Dried apricots packed in polyethylene packs in a
Moisture content
The effect of storage on the moisture content of irradiated sun-dried apricots was determined every month at 1.0, 2.0, 3.0, 4.0, and 5.0 kGy. Table 1 demonstrates that the moisture content of control and irradiated sun-dried apricots immediately after irradiation varied from 14.33%±0.068% to 14.87%±0.094%. The moisture content increased at different time points of storage at each dose applied. The increase was significant up to the first 8 months of storage in all treatments except in 4.0 and 5.0
Conclusion
EB irradiation processing at 3.0 kGy proved to be an effective post-harvest treatment for the quality maintenance of sun-dried apricots. Radiation treatment of dried apricots at 1.0–3.0 kGy proved beneficial in the retention of high levels of β-carotene, ascorbic acid, and color values without impairing taste. Doses of 1.0–3.0 kGy retained the β-carotene content of sun-dried apricots to 8.21, 9.27, and 10.43 compared with 6.09 in control samples after 10 months of storage. During storage, a
Acknowledgments
This work was supported by the National Science and Technology Supported Program during the Twelfth Five-year Plan Period for the Agricultural Field (2011BAD27B01).
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