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Shelf-life Extension of Bread by Heat and Irradiation Treatment

F. Begum
Institute of Food and Radiation Biology, Atomic Energy Research Establishment, Savar, Dhaka-1000, Bangladesh.

A. K. Siddique
Institute of Food and Radiation Biology, Atomic Energy Research Establishment, Savar, Dhaka-1000, Bangladesh.

N. Choudhury
Department of Microbiology, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Bread slices were given irradiation treatment of 0.5, 1.0, 1.5 and 2.0 KGy and heat treatment at 60°C for 20 min to control mould growth. Mould growth was retarded at ambient temperature by 3, 4, 6 and 8 days after 0.5, 1.0, 1.5 and 2.0 KGy treatments, respectively, compared to 2 days in case of control sample and 3 days for heat treatment alone. Combination of heat with irradiation at 0.5, 1.0, 1.5 and 2.0 KGy retarded mould growth up to 4, 6, 7 an 9 days, respectively. Organoleptically, the irradiated bread slices were acceptable up to 3 to 6 days depending on the treatment. The combination method treated slices were acceptable up to 8 days. The application of radiation dose exceeding 2.0 KGy caused off flavour. Mild heat treatment and radiation in combination resulted in a synergistic antifungal effect and enhanced shelf-life of bread.

Keywords: Self life, Bread, Heat treatment

Location: Institute of Food and Radiation Biology, Atomic Energy Research Establishment, Savar

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Bread

Objectives:

To determine the antifungal effect and enhanced shelf-life of bread by heat and irradiation treatment.

Methodology:

Sliced bread of a popular b-and, 24-h old, was procured from retail shops. Bread slices were divided into four groups with four slices in each group; one group served as control, one group was irradiated at different doses of radiation, another was given heat treatment at 60°C for 20 min and the third group was given a combination of heat and irradiation. The bread slices were packaged in polyethylene pouches and three replicates were kept for each treatment. For heat treatment, bread slices were kept at 60°C in an oven for 20 min after which the slices were packed in pouches. Irradiation treatment was given from a 60eo, 50,000 Ci gamma source (Gammabeam-650, AECL, Canada), and the doses applied were 0.5, 1.0, 1.5 and 2.0 KGy. The samples were then stored at room temperature and analysed for mould and bacterial growth and sensory properties. For total microbial counts, 20 g of bread was suspended in 180 ml distilled water from which pour-plates were made on nutrient agar medium at p^H 7.0. Total mould count was determined on potato-dextrose agar at p^H 5.2. Sensory properties of bread samples were evaluated periodically by a 9-point hedonic scale, ranging from "Like extremely" to "Dislike extremely".

Source of Information: Bangladesh Journal of Microbiology, Vol-11, No-1, Page:31-35,

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results of organoleptic evaluations are shown in Both treated and untreated bread slices were evaluated for colour, flavour, texture and taste by a panel of four judges on 3, 6 and 9 days of storage. Bread samples treated with 1 KGy and above and by the combination method were acceptable on 6 day of storage and samples given 1.5 KGy with and without heat showed no signs of spoilage till 9 days of storage when organoleptic evaluation was discontinued. Combination of 1.5 KGy irradiation treatment with 60°C heat treatment resulted in higher organoleptic score compared to all other treatment.

Knowledge Management: Journal