Cooking Quality of Brown Rice as Influenced by Gamma Irradiation, Variety and Storage

Two long grain and one medium grain brown rice varieties were gamma-irradiated at 1.0 and 2.0 kGy to ascertain if cooking time could be decreased and to determine effects of storage on chemical and physical characteristics. A tendency toward decreased cooking time was observed as dose level increased. Cooking time was not significantly (P> 0.05) affected by storage. A trend was noted in water uptake ratios, soluble starch of residual cooking water and volume expansion due to irradiation. Storage of irradiated rice produced similar changes to those of nonirradiated rice. Variety also contributed to differences in irradiated samples, such as cooking times, water uptake, starch retention and grain volume expansion.     

Effect of Gamma Irradiation on Molecular Structure and Physicochemical Properties of Corn Starch

ABSTRACT:  Carboxyl content and amylose leaching of gamma-irradiated corn starch increased and swelling factor decreased with increasing radiation dose. The apparent amylose content decreased gradually from 28.7% for native starch to 20.9% for 50 kGy irradiated starch. The proportion of short amylopectin branch chains (DP 6 to 12) increased, while the proportion of longer branch chains (DP ≥ 37) decreased with increasing radiation dose. The relative crystallinity and the degree of granule surface order decreased from 28.5% and 0.631 in native starch to 26.9% and 0.605 in 50 kGy irradiated starch, respectively. Pasting viscosity and gelatinization temperatures decreased with an increase in radiation dose. At a high dose (50 kGy), melting of amylose–lipid complex in DSC thermogram was not observed. The rapidly digestible starch (RDS) content slightly decreased up to 10 kGy but increased at 50 kGy. The resistant starch (RS) content slightly decreased at 2 kGy and then increased up to 50 kGy. The slowly digestible starch (SDS) content showed the opposite trend to RS content. Slower irradiation dose rate reduced carboxyl content, swelling factor, and amylose leaching. The apparent amylose content and amylopectin chain length distribution were not significantly affected by dose rate of gamma irradiation. However, the relative crystallinity and gelatinization enthalpy increased with slower dose rate. Slower dose rate decreased RDS and SDS contents, and increased RS content.     

电子束辐照防治绿豆象及对绿豆品质的影响

为完善辐照技术防治储粮虫霉的理论,研究了电子束辐照对绿豆象种群发育及对绿豆品质的影响。绿豆象的卵、幼虫、蛹和成虫经0.1~1.0 kGy剂量的电子束辐照后,卵和幼虫在辐照的虫态死亡;蛹发育至成虫和成虫的死亡率显著增加,其种群存活个体的产卵总量显著减少;辐照处理种群的F1代不能孵化为幼虫或在1~2龄幼虫时全部死亡,而0.2 kGy及以上的辐照剂量则能完全抑制F1代孵化为幼虫。尽管0.2kGy的辐照剂量使绿豆的苗高下降了17%,脂肪酸值升高了12%,但对其发芽率、发芽势、可溶性蛋白质含量、降落数值和过氧化氢酶活性无显著影响,并且提高了绿豆的糊化液黏度。因此,推荐0.2 kGy的电子束辐照作为有效防治绿豆中绿豆象的参考剂量。     

Quality of packaged romaine lettuce hearts exposed to low-dose electron beam irradiation

We investigated the effects of low-dose electron beam irradiation (1.0, 1.5 and 3.2 kGy) on the quality of commercially prepackaged fresh romaine lettuce hearts. The impact of the irradiation treatment on the functionality of the package was also evaluated. Irradiated samples showed slight changes in color, but these changes were not significantly different (P >0.05) from the nonirradiated (control) samples. Sample firmness decreased by 49.58% (leaves) and 29.13% (ribs), as the dose level increased. Sensory attributes such as overall quality, color, sogginess, and off-flavor were found less acceptable at the higher dose level. Irradiation affected the respiration rates inside the packages, with lower (10.38%) O₂ and higher CO₂ levels than the control. Irradiation at 1.5 and 3.2 kGy dose levels improved the oxygen barrier capability of the low-density polyethylene (LDPE) bags (7.67% and 4.48%, respectively). Water vapor permeability was unaffected at all the irradiation dose levels. The stiffness of LPDE films did not change due to irradiation treatment. Results from sensory evaluation of produce overall quality suggest a potential fungicidal effect of low-dose irradiation (1.0 kGy) of packaged romaine lettuce hearts without altering the overall quality of the produce as well as the LDPE-packaging characteristics.     

Extrusion cooking properties of white and coloured rice varieties with different amylose content

Five white and coloured rice varieties with different AM contents (long grain rice: 34%, Thai Jasmine rice: 15%, glutinous rice: 7%, red rice: 18% and black rice: 5%) were pregelatinised using a twin‐screw extruder at a barrel temperature of 150°C and two levels of feed moisture (12 and 16%). The correlation of AM content to water absorption index (WAI), water solubility index (WSI), starting viscosity, hot viscosity and final viscosity of the five rice extrudates were determined. Total anthocyanin content (TAC), total phenolic content (TPC) and antioxidant activity of extrudates were analysed by spectrophotometric methods. AM content was positively correlated to WAI and final viscosity. High AM content of the rice varieties resulted in high WAI and high final viscosity of extrudates. In addition, higher feed moisture content (16%) increased WAI and pasting properties of rice extrudates, but decreased WSI. Extrusion cooking reduced TAC, TPC and antioxidant properties, but the remaining values were high enough to suggest a further use for (functional) food production.     

Moisture-mediated effects of γ-irradiation on antioxidant properties of mung bean (Vigna radiate L.) cultivars

The present investigation is the very first report about the effect of γ-irradiation along with moisture on antioxidant properties of mung bean. Mung bean cultivars were conditioned to moisture level of 10 (control), 12, and 14% and treated with different doses of γ-irradiation (1.0, 2.5, and 5.0 kGy). The total phenolic content (TPC) decreased upon very low (1 kGy) and low dose (2.5 kGy) of γ-irradiation while significantly increased upon further increase in dose (5 kGy) at 10% moisture. However, γ-irradiation (1 and 2.5 kGy) at 12% moisture increased the TPC by 8 and 9%, respectively, and at 5 kGy dose lowered by 15% as compared to control. Antioxidant activity (AOA) was decreased by 10% (1 kGy and 10% moisture) and increased by 13% (5 kGy and 10%) while significantly increased at all doses (at 12%) by 106%. Total flavonoids content and reducing power also affected significantly upon γ-irradiation at various moisture.Industrial relevanceThe present investigation is the first report revealing the impacts of moisture-mediated γ-irradiation of mung bean. Since γ-irradiation is a popular method for safe storage of food including legumes and cereals, the moisture content between 10 and 14% was considered safe for grain storage. But γ-irradiation of mung bean at these levels of moisture significantly changed the antioxidant potential. By selecting suitable moisture content and dose of γ-irradiation, the antioxidant potential of mung bean may be improved to get the maximum health benefit. Therefore, the legume processing industry can utilize these combinations (moisture and dose of irradiation) to improve the antioxidant properties of mung bean.     

The Influence of Electron Beam Irradiation on the Effectiveness of Trans-cinnamaldehyde-coated LDPE/Polyamide Films

ABSTRACT:  We have evaluated the effect of electron beam irradiation (up to 20 kGy) on the functional and barrier properties of trans-cinnamaldehyde-coated low-density polyethylene (LDPE)/polyamide films. Irradiation did not affect the tensile strength and toughness of the films, but the 20 kGy treatment increased the percent elongation-at-break significantly. The barrier properties were also enhanced (approximately 18.8%) when the films were exposed to 20 kGy. Addition of trans-cinnamaldehyde with 3% of polyamide coating solution (w/w) did not affect the tensile strength and barrier properties of the films, but significantly decreased the percent elongation-at-break and toughness. Films with 3% and 10% coating were used to wrap fresh-cut romaine lettuce samples to determine their antimicrobial activity. Total aerobic plate count (APC) and yeast and mold growth were determined as a function of dose (0, 0.5, and 1.0 kGy) for 14 d of storage at 4 °C. Irradiation reduced the total APC and yeast and mold counts (YMC) as dose increased. The 0.5- and 1.0-kGy treatments decreased initial APCs by 1.2- and 1.5-logs, and no YMCs were observed in the 1.0-kGy treated samples at day 0. Irradiation exposure significantly lowered APCs of lettuce samples by almost 1-log colony-forming unit (CFU)/g compared to the nonirradiated controls, though it only slightly reduced YMCs. The effectiveness of using irradiation with antimicrobial films was enhanced with increased radiation dose and trans-cinnamaldehyde concentration (3% to 10%).     

EFFECTS OF GAMMA IRRADIATION ON ASPECTS OF MILLED RICE (ORYZA SATIVA) END‐USE QUALITY1

In China, breeding efforts to create Indica‐type rice cultivars with textural and functional properties similar to Japonica‐type rice have not been successful. An alternative strategy is to develop a processing method to modify the end‐use quality of Indica‐type rice. Milled rice samples with low, intermediate and high apparent amylose content (AAC) were treated with ⁶⁰Co gamma rays. AAC was impacted only by high doses of gamma rays while gel consistency was significantly increased. Increasing levels of gamma irradiation (GIR) reduced rice flour viscosity and increased the temperature of gelatinization onset. Exposure to gamma rays caused the RVA setback (rice pasting properties) but not the instrumental texture properties of an Indica‐type cultivar to become more like that of the Japonica‐type rice. GIR of milled rice for human consumption would be limited to between 2 and 4 kGy because of its negative effects at higher doses on rice color and aroma. However, that level will destroy insects and some microorganism and change rice of unacceptable quality for some consumers closer to being acceptable and may also broaden the functionality of rice for industrial uses.     

Effects of electron‐beam irradiation on physicochemical properties of starches separated from stored wheat

Effects of electron‐beam irradiation (0, 1.0, 2.7, and 4.4 kGy) on physicochemical properties, MW distribution as well as microstructure of starches separated from electron‐beam irradiated and stored wheats were investigated by differential scanning calorimeter (DSC), SEM, and static multi‐angle laser light scattering (MALLS). The profiles of starch viscosity illustrated that peak, hot paste, cold paste, and setback were considerably decreased with increasing irradiation dose. The DSC pattern indicated that the electron‐beam irradiation caused a slight decrease in gelatinization temperature. SEM results showed that on the surfaces of a few starch granules fissures appeared and that they become rough when the irradiation doses reached 4.4 kGy. Damaged starch (DS) contents analysis suggested that the DS increased from 5.33 to 7.38% as the dose increased from 0 (control) to 4.4 kGy. HPSEC measurement showed that the starch molecule were gradually degraded due to the electron‐beam irradiation treatment, and the molar mass of wheat starches decreased by one order of magnitude when the irradiation doses reached 4.4 kGy.     

Influence of gamma-irradiation and maize lipids on the production of aflatoxin B1 by Aspergillus flavus

The effect of gamma-irradiation and maize lipids on aflatoxin B1 production by Aspergillus flavus artificially inoculated into sterilized maize at reduced water activity (aw 0.84) was investigated. By increasing the irradiation doses the total viable population of A. flavus decreased and the fungus was completely inhibited at 3.0 kGy. The amounts of aflatoxin B1 were enhanced at irradiation dose levels 1.0 and 1.5 kGy in both full-fat maize (FM) and defatted maize (DM) media and no aflatoxin B1 production at 3.0 kGy gamma-irradiation over 45 days of storage was observed. The level in free lipids of FM decreased gradually, whereas free fatty acid values and fungal lipase activity increased markedly by increasing the storage periods. The free fatty acid values decreased by increasing the irradiation dose levels and there was a significant enhancement of fungal lipase activity at doses of 1.0 and 1.50 kGy. The ability of A. flavus to grow at aw 0.84 and produce aflatoxin B1 is related to the lipid composition of maize. The enhancement of aflatoxin B1 at low doses was correlated to the enhancement of fungal lipase activity.