Elsevier

Food Chemistry

Volume 87, Issue 3, September 2004, Pages 377-382
Food Chemistry

Effect of gamma irradiation and temperature on fructans (fructo-oligosaccharides) of stored onion bulbs Allium cepa L

https://doi.org/10.1016/j.foodchem.2003.12.010Get rights and content

Abstract

The effects of gamma irradiation doses and temperatures on fructo-oligosaccharides of onion bulbs after six months storage were investigated. Bulbs were ionized at doses of 0.15 and 0.30 kGy, and kept at 4, 10 and 20 °C during 24 weeks. The concentrations of glucose, fructose, sucrose and other fructo-oligosaccharides were then determined. Fructans content decreased with degree of polymerization (DP), and glucose, fructose and sucrose constituted major proportions of total carbohydrates, averaging 28%, 24% and 10%, respectively. Trisaccharides averaged 12%, while tetra-saccharides averaged 10% of total carbohydrates. High polymerized fructo-oligosaccharides averaged 13% for DP 5–8 and 5% for DP up to 12 U. After six months, glucose, fructose and sucrose of control and both irradiated bulbs decreased slightly but not significantly, while temperature and irradiation significantly influenced fruco-oligosaccharides of bulbs.

Introduction

Onions with other members of the Alliums family are generally consumed for their flavour, and their nutritive value has only been recently appreciated (Salunkhe & Wu, 1974). During their harvesting, handling, transportation, packaging and storage, onion bulbs are exposed to several treatments and environmental conditions which can affect their quality attributes and physiological characteristics. These effects could be responsible for several reactions and stresses, causing important biochemical changes to the bulb tissues (Benkeblia, 2003).

Bulb dry matter content is an important quality parameter of onion, and several investigations have attempted to relate bulb characteristics and storage life (Rutherford & Whittle, 1984). About 80% of bulb dry matter are non-structural carbohydrates (Darbyshire & Henry, 1981). The predominant members of these non-structural carbohydrates are glucose, fructose, sucrose and low-molecular-weight fructans, while starch and raffinose are absent (Benkeblia, Varoquaux, Shiomi, & Sakai, 2002; Darbyshire & Henry, 1981). The metabolism of sugars is closely linked to the dormancy and sprouting state (Kato, 1966), and the most important biochemical changes occurring during long term storage of bulbs, as of other vegetables, are the quantitative variations in the carbohydrate constituents. Variations of mono and disaccharides levels in onion bulbs during storage were previously reported (Benkeblia et al., 2002; Benkeblia & Varoquaux, 2003; Hurst, Shewfelt, & Schuller, 1985; Rutherford & Whittle, 1982); however, variation of fructo-oligosaccharides and the effect of gamma irradiation and long term storage on these constituents were not investigated.

Ionizing radiation is defined as a process in which food products are exposed to a controlled amount of radiant energy. Irradiation increases shelf life of fruits and vegetables, and reduces spoilage, and several investigations have been carried out throughout the world on the use of ionizing radiation to control sprouting in onions (Elias & Cohen, 1983; Matsuyama & Umeda, 1983). Irradiation doses ranging from 0.05 to 0.15 kGy inhibit bulb sprouting, and are more effective when applied during the dormancy period, specifically within 4–6 weeks following harvesting (Salunkhe & Wu, 1974). Ionized bulbs can be stored for several months without heavy spoilage, though ionization and storage can affect changes in the carbohydrate contents of onion tissues. However, despite the existence of numerous data on the commercial quality of irradiated onion bulbs, little information is available about the pattern of changes in the main chemical components, such as non-structural carbohydrates, during irradiation treatments and long-term storage.

The aim of this investigation was to assess the effect of irradiation and long-term storage on dry onion bulbs. Two irradiation doses were used (0.15 and 0.30 kGy) and treated bulbs were stored at three different temperatures (4, 10 and 20 °C) for 24 weeks. The concentrations of glucose, fructose, sucrose and other fructo-oligosaccharides were then determined.

Section snippets

Onions

Dry onion bulbs Allium cepa cv. Jaune d’Espagne (organic product, free of any preharvest chemical treatments), which had been freshly harvested and dried in the field for 2 weeks, were obtained from the local market. They were sorted for uniformity and absence of defects, packed in commercial plastic (PVC) trays and placed at 18 °C prior to treatments. Each tray contains 12 kg onions, and three trays were used for each irradiation dose and temperature.

Ionizing treatment

The irradiation treatment was applied two

Results

As shown in Fig. 1, glucose, fructose and sucrose constitute a major proportion of non-structural carbohydrates, while tri- and tetra-saccharides contents are lower. It was observed that concentration of high polymerized fructans decreased with their degree of polymerization. The distribution of the carbohydrate constituents is shown in Table 1. It was noted that glucose, fructose and sucrose constitute of a major part of the dry matter and non-structural carbohydrates, averaging 28%, 24% and

Discussion

Variation of mono and disaccharides in onions, particularly irradiated bulbs, was not extensively studied. Salama, Hicks, and Nock (1990) reported a decrease in total sugars and glucose in control onions stored for 5 months at 0, 15 and 30 °C, but fructose increased, particularly at 0 °C. Similar results on fructose were reported by Rutherford and Whittle (1982) at 0 °C. Hurst et al. (1985) noted a decrease in total sugars of onion kept during 6 months at 1 and 4 °C, but no variation was noted

Acknowledgments

Part of this work was conducted during a Postdoctoral Fellowship from the Japanese Society for the Promotion of Science (JSPS).

References (16)

  • N. Benkeblia et al.

    Changes in oligosaccharides, phenolics and peroxidase activity in inner bud of onion bulbs during break of dormancy by low temperatures

    Acta Agriculturæ Scandinavica

    (1999)
  • N. Benkeblia et al.

    Respiratory parameters of onion bulbs. Effects of irradiation and temperature

    Journal of the Science of Food & Agriculture

    (2000)
  • N. Benkeblia et al.

    Effect of irradiation, MH and CIP treatments on respiration rate and oligosaccharides variations in onion bulbs in store

    International Journal of Food Science & Technology

    (2002)
  • N. Benkeblia et al.

    Effect of γ irradiation, temperature and storage time on glucose, fructose and sucrose status of onion bulbs Allium cepa L

    International Agrophysics

    (2003)
  • N. Benkeblia

    Postharvest technology of onions

  • B. Darbyshire et al.

    Differences in fructan content and synthesis in some Allium species

    New Phytologist

    (1981)
  • P.S. Elias et al.

    Recent advances in food irradiation

    (1983)
  • W.C. Hurst et al.

    Shelf-life quality changes in summer storage onions (Allium cepa)

    Journal of Food Science

    (1985)
There are more references available in the full text version of this article.

Cited by (27)

  • Influence of propagation method and storage conditions on fructo-oligosaccharide degradation in onions (Allium cepa L.)

    2021, Journal of Food Composition and Analysis
    Citation Excerpt :

    Storage under controlled atmosphere, i.e. reducing oxygen to 0.5 % at 2 °C was most effective in slowing down FOS degradation during 27 and 36 weeks of storage (Ernst et al., 2003). Storage at lower temperatures (under 10 °C and 20 °C) has been reported to slow down the degradation of FOS (Benkeblia et al., 2004a, 2005a). Other studies, however, reported that low temperatures did not slow down FOS hydrolysis, and FOS degradation largely depended on the physiological demand during sprouting and tissue growth (Benkeblia et al., 2007).

  • Enhancement of fructan extraction from garlic and fructooligosaccharide purification using an activated charcoal column

    2021, LWT
    Citation Excerpt :

    Enzyme-treated garlic pulp fructan was extracted using three different methods: 1) hot water, 2) ethanol, and 3) methanol. Many different combinations of solvent ratio, time, and temperature were optimized by distinct researchers for fructan extraction (Darbyshire & Henry, 1978; Suzuki & Cutliffe, 1989; Pontis, 1990, pp. 353–369; Jaime et al., 2000; Jaime et al., 2001; O'donogue et al., 2004; Benkeblia, Onodera, & Shiomi, 2004; Benkeblia, Onodera, Yoshihira, et al., 2004; Benkeblia, Onodera, & Shiomi, 2005; Benkeblia, Ueno, et al., 2005; Chope et al., 2006; Chope et al., 2007a; Chope et al., 2007b; Sanz & Martínez-Castro, 2007; Davis et al., 2007; Vagen & Slimestad, 2008; Downes & Terry, 2010; Benkeblia, 2013; Magwaza & Opara, 2015; Matros et al., 2019). The particular three methods of extraction adopted in this study were selected from those in literature based on their choice of solvents, temperature, and time, taking into consideration employed the maximum yield of fructan in the different extraction procedures.

  • MALDI-TOF/TOF tandem mass spectrometry imaging reveals non-uniform distribution of disaccharide isomers in plant tissues

    2021, Food Chemistry
    Citation Excerpt :

    The lateral resolutions of these images are relatively lower than some published animal tissue, due to intrinsic characters of plant tissue, such as complex texture, low lipid and high water content (He et al., 2019; Li, Zhang, Ge, Liu, & Li, 2018). Though most studies of the disaccharide in onion was on sucrose (Benkeblia et al., 2004; Pohnl, Schweiggert, & Carle, 2018), the presence of other disaccharide isomers have been demonstrated in this work and disaccharide isomers exhibited distinct distributions within onion bulb. The observation was also found in another purple onion bulb tissue (Fig. S5), exclude the possibility of artificial results.

View all citing articles on Scopus
View full text