Post-harvest kernel discoloration and fungi activity in long-grain hybrid, pureline and medium-grain rice cultivars as influenced by storage environment and antifungal treatment

Shad, Zeinab Mohammadi; Atungulu, Griffiths G.

doi:10.1016/j.jspr.2019.02.002

Cited by 21 publications

(10 citation statements)

References 16 publications

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“…The water activity was not significantly affected by EB irradiation and storage conditions. The consistency of water activity during storage at different temperatures and storage durations is in agreement with a study done by Mohammadi Shad and Atungulu () on the same hybrid rice used in the current study.…”

Section: Resultssupporting

confidence: 92%

“…But when nonirradiated rice was stored at 40°C, discoloration of 23.1 ± 2.50% occurred just after 2 weeks and approached 100% discoloration after 8 weeks of storage. The discoloration trend was consistent with the rice storage study by Mohammadi Shad and Atungulu () who found complete discoloration in milled rice (XL753) after 16 weeks of the rough rice storage, regardless of MC. Discoloration of the EBI rice stored at 20 and 30°C for 2 weeks increased by 47.9% and 66.2%, respectively, compared to the control samples.…”

Section: Resultssupporting

confidence: 90%

“…Similarly, Atungulu, Zhong, Thote, Okeyo, and Couch () found TMC of 6.26 and 5.97 log CFU/g for the XL753 rice, harvested in 2013 and 2014, respectively. The same level of initial TMC in rice was also reported by Mohammadi Shad and Atungulu () who found TMC in a range of 5.3–6.3 log CFU/g.…”

Section: Resultssupporting

confidence: 85%

“…However, subsequent investigations have refuted the role of mold in rice discoloration. For instance, Mohammadi Shad and Atungulu (); Belefant‐Miller et al (); Phillips, Widjaja, Wallbridge, and Cooke (); Schroeder () revealed no correlation between the mold presence and rice discoloration. Hence, the research community has no concession on the exact role of microbes on rice discoloration.…”

Section: Introductionmentioning

confidence: 99%

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Biochemical changes associated with electron beam irradiation of rice and links to kernel discoloration during storage

et al. 2019

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Background and objectives: Rice kernel discoloration during storage results in significant economic losses to rice growers and processors. This study aimed to elucidate the extent of chemical changes and microbial involvement on discoloration of rice kernels during storage. To segregate and/or diminish the effects of microbes, one lot of hybrid long-grain rice (XL753) samples was irradiated with nonthermal electron beam (EB) dose of 14 kGy. The irradiated and nonirradiated control samples of rice at a moisture content (MC) of 21% on a wet basis were stored at three temperatures (20, 30, and 40°C) for 8 weeks. Samples were taken every 2 weeks for microbial and chemical analyses. Findings: A negative relationship was noted between discoloration and microbial load. The trend of increasing discoloration and chemical properties such as free sugars, free fatty acid, and free 5-hydroxymethyl-2-furaldehyde (HMF), especially at higher storage temperatures and durations, suggested that biochemical changes were major drivers of the observed rice discoloration. The higher HMF in highly discolored rice (≥20%) explained nonenzymatic browning in the rice matrix during storage. Conclusions: From this study, it was drawn that the rice kernel discoloration was not directly related to the microbial load; the discoloration was seen in EBI rice even with 99% reduction in microbial load. However, it was clarified that the rice discoloration especially in EBI rice samples was related to the observed chemical changes, which were also storage temperature dependent. Significance and novelty: Milled rice discoloration during storage of rough rice is insufficiently understood. There is no information correlating changes in chemical attributes and microbial activity to discoloration of contemporary hybrid rice during storage. Therefore, the results of the current study provide important fundamental information and also suggest storage conditions required to arrest discoloration and maintain quality of contemporary milled hybrid rice. K E Y W O R D Schemical changes, microbes, postharvest treatments, rice kernel discoloration, storage | 825 MOHAMMADI SHAD et Al.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Biochemical changes associated with electron beam irradiation of rice and links to kernel discoloration during storage

et al. 2019

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“…In order to satisfy import/export demand and supply, huge amount of rice is stored after harvest, often more than a year (Fleurat‐Lessard, ). When rice is stored in an inappropriate condition, it is susceptible to microbial contamination that directly or indirectly affects quality and safety of the stored rice (Mohammadi‐Shad & Atungulu, ). Depending on storage conditions, microorganisms may metabolize and proliferate on rice leading to formation of musty odors, dry matter loss, kernel discoloration, and mycotoxin contamination (Atungulu, Mohammadi‐Shad, & Wilson, ; Atungulu, Zhong, & Siebenmorgen, ; Christensen & Kaufmann, ; Suleiman, Rosentrater, & Bern, ).…”

Section: Introductionmentioning

confidence: 99%

Impacts of broadband and selected infrared wavelength treatments on inactivation of microbes on rough rice

Oduola¹,

Bowie²,

Wilson³

et al. 2020

Journal of Food Safety

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This study investigated the effects of broadband and selected infrared (IR) wavelength treatments of rough rice on microbial inactivation. Rough rice was treated at different IR wavelengths and product‐to‐emitter distances (110, 275, and 440 mm) followed by tempering at 60°C for 4 hr. The total mold and aerobic plate counts (APC) on non‐treated and treated samples were determined. Significant total mold reductions of 1.14 and 3.11 log CFU/g were obtained after IR heating using broadband and selected wavelengths, respectively (p < .05). The most significant reduction of APC using selected IR wavelength was 1.09 log CFU/g; the broadband IR wavelength had no effect on the mean APC. The IR treatments followed by tempering step resulted in greater reductions of total mold counts and APC (4.03 and 3.50 log CFU/g) in comparison to IR treatments without tempering (3.11 and 1.09 log CFU/g). Overall, bacteria showed more resistance to IR treatments than molds.

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Impact of kernel thickness on parboiled rice properties

et al. 2020

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Background and objectiveApproximately 15% of the rice produced in the world is parboiled. Parboiling, a hydrothermal process involving soaking, steaming, and drying, is conventionally utilized to improve milling quality, nutritional value, and shelf life of rice. Because rice is composed of kernels of varying thickness, rice kernel thickness may impact parboiled rice properties. This study investigated the milling and color properties of parboiled rice prepared from two rice cultivars with different kernel thickness distributions and chemical compositions by subjecting them to different soaking temperatures and durations.FindingsRoyJ was composed of a greater proportion of thinner kernels, whereas XL756 was composed of a greater proportion of thicker kernels. The head rice yield (HRY) of the resultant parboiled rice was strongly affected by rice cultivar and thickness fraction, but was not impacted by their chemical compositions. RoyJ had a greater HRY than XL756 for the same thickness fraction under the same soaking conditions. Lightness (L*) and yellowness (b*) appeared to be greatly affected by cultivar with RoyJ displaying greater L* and b* values than XL756 for most conditions.ConclusionKernel thickness and soaking duration were important factors affecting the HRY of parboiled rice for both rice cultivars. Rice cultivars composed of a greater percentage of thinner kernels would be more susceptible to severe parboiling conditions and thus produce more variation in the HRY of parboiled rice.Significance and noveltyThe distribution of kernel thickness is different for different rice cultivars and should be taken into consideration when choosing parboiling conditions to maximize the HRY of parboiled rice.

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Post-harvest kernel discoloration and fungi activity in long-grain hybrid, pureline and medium-grain rice cultivars as influenced by storage environment and antifungal treatment

Cited by 21 publications

References 16 publications

Biochemical changes associated with electron beam irradiation of rice and links to kernel discoloration during storage

Biochemical changes associated with electron beam irradiation of rice and links to kernel discoloration during storage

Impacts of broadband and selected infrared wavelength treatments on inactivation of microbes on rough rice

Impact of kernel thickness on parboiled rice properties

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