Elsevier

Radiation Physics and Chemistry

Volume 97, April 2014, Pages 126-133
Radiation Physics and Chemistry

Electron beam irradiation of sun-dried apricots for quality maintenance

https://doi.org/10.1016/j.radphyschem.2013.11.019Get rights and content

Highlights

  • Electron beam irradiation was used for sun-dried apricots quality maintenance.

  • The chemical, sensory, and microbial quality parameters of apricots were evaluated.

  • 1.0–3.0 kGy proved to be beneficial for retaining high levels of apricots quality.

  • 3.0 kGy of irradiation maintained a high overall acceptability of sun-dried apricots.

  • 3.0 kGy of irradiation reduced the viable microorganisms to below detection limits.

Abstract

The chemical, sensory, and microbial quality parameters of electron beam (EB)-irradiated and non-irradiated sun-dried apricots were periodically evaluated to optimize the EB irradiation of sun-dried apricots for quality maintenance. The sun-dried apricots were treated with 1.0, 2.0, 3.0, 4.0, and 5.0 kGy of EB and subsequently stored at ambient temperature. EB treatment at 1.0–3.0 kGy proved to be beneficial for retaining high levels of β-carotene, ascorbic acid, titratable acidity, total sugars, and color without any significant effect on sensory properties. 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. After 10 months of storage, the maximum losses of ascorbic acid were 37.8% in control samples and 35.5% in 3.0 kGy-irradiated samples. Titratable acidity and total sugars were significantly enhanced immediately after 1.0–3.0 kGy irradiation treatment, and both parameters showed no significant change after 10 months of storage. Samples subjected to EB treatment at 3.0 kGy maintained a high overall acceptability of sun-dried apricots. Decreased number of viable microorganisms to below detection limits were observed after 3.0 kGy irradiation, and compared with the control, the logarithmic reductions after 10 months of storage were 0.98 for yeast and mold count, as well as 1.71 for bacterial count.

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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