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Biochemical Composition and Effects of Radiation on Sensory, Biochemical and Physiological Quality of Fresh Spinach (spinacia Oleracea L.)

Fatema Akhter
Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Mahfuza Islam
Food Technology Division, IFRB, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh

Afifa Khatun
Food Technology Division, IFRB, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh

M. Kamruzzaman Munshi
Food Technology Division, IFRB, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh

Md. Afzal Hossain
Food Technology Division, IFRB, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh

Mozammel Hoque
Department of Food Engineering and Tea Technology, Shahjalal University of Science and Technology, Sylhet, Bangladesh

Roksana Huque
Food Technology Division, IFRB, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh

Abstract/ Executive Summary:

Leafy vegetables have become an important part of the diet because of their nutritive value and low calorie content. But leafy vegetables are very perishable and susceptible to postharvest damage and spoilage which limit the storage period and quality of them. Irradiation is being used in the preservation of leafy vegetables. The effects of irradiation (0.5 and 1.0 kGy) on sensory, biochemical, physiological attributes of spinach were investigated during 12 days of post-irradiation storage at 12°C ± 60% RH. Spinach treated with 1.0 kGy showed acceptability in color, flavor, texture and overall acceptability till 12 days during storage period whereas at the same period, control and 0.5 kGy treated samples were spoiled. Reduced rate of weight loss was observed in irradiated samples compare to control over the whole storage period. A minor decrease in the ascorbic acid content was the only adverse effect observed in irradiated spinach compare to control sample and no other major changes occurred in TSS, pH value of treated and untreated sample of spinach. Radiation processing of spinach at 1.0 kGy extends the shelf life without affecting sensory and nutritional qualities. Thus, radiation can be used for the shelf -life extension of leafy vegetables and is not harmful to health.

Keywords: Spinach, Irradiation, Sensory, Biochemical and physiological quality

Location: Institute of Food and Radiation Biology (IFRB), Atomic Energy Research Establishment, Savar, Dhaka

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Spinach

Objectives:

The present study was attempted to evaluate effect of gamma radiation to extend the shelf life and to improve biochemical (ascorbic acid, total soluble solid, pH value) and physiological quality (weight loss) of fresh spinach stored at 12º C for 12 days.

Methodology:

Plant material- Spinach (Spinachia oleraceae L.) of good quality were collected from the local market and transported to the laboratory. After discarding the damaged and wilted leaves, spinach leaves were selected for uniformity of size, shape and colour, and without any defects or mechanical injury. Irradiation - After discarding the damaged and wilted leaves, spinach leaves were selected for uniformity of colour and without any defects or mechanical injury. For each treatment 25-30 g of spinach was placed into polythene bags (25 cm X 16 cm) and sealed tightly. The sealed polythene bags were labeled by indicating the name of the product and were irradiated with two selected doses of gamma radiation which were 0.5 kGy and 1.0 kGy. Irradiation was applied to the samples with a 50kCi Co⁶⁰ gamma source (dose rate 6.4 kGy / hr) located at Institute of Food and Radiation Biology (IFRB), Atomic Energy Research Establishment, Savar, Dhaka. Both treated and untreated samples were stored at 12°C temperature for 12 days. The both samples were analyzed at every three days interval for visual and chemical analysis. Sensory evaluation - A quantitative affective test was used to determine liking and attitude of irradiated spinach because it would show whether irradiation affected acceptance (liking) by consumers. Sensory evaluation of all formulated spinach was done by taste tasting panel using the Hedonic scales suggest by (Krum, 1955). A panel of ten judges with age ranging from 25-40 years was made on their consistency and reliability of judgment. They were asked to evaluate color, flavor, and texture scoring rate on a 9 points Hedonic scale, where, 0-2 represent disliked extremely, 3-5 for dislike, 6-8 for acceptable or good and 9 for excellent color, flavor and texture. The preference differences were evaluated by statistical analysis of the data for variance. Estimation of moisture - At first, the initial weight of the samples was taken. Then samples were dried in an oven at about 105° C for about 5-6 hours until a constant weight was reached and cooled in a desiccator and weight again. The percentage of moisture content was calculated by the following equation: Percentage (%) of moisture = (Final weight – Initial weight /Original weight of sample) × 100. Estimation of protein - Protein content was determined by by micro-Kjeldahl’s method was developed. It involves conversion of organic nitrogen to ammonium sulphate by digestion with concentrated sulphuric acid in a microkjeldahl flask. The digest was diluted, made alkaline with sodium hydroxide and distilled. The liberated ammonia was collected in a boric acid solution and was determined titrametrically. The percentage of protein in the sample was calculated by the following equation: Percentage (%) of protein = (c-b) × 14 × d × 6.25/a × 1000 × 100, Where, a = sample weight (g), b= volume of NaOH required for back titration and neutralize 25ml of 0.1N H₂SO₄ (for sample), c= volume of NaOH required for back titration and neutralize 25 ml of 0.1N H₂SO₄ (for blank), d=normality of NaOH used for titration, 6.25= conversion factor of N to protien, 14= atomic weight of N. Estimation of ash - The ash content of a sample is the residue left after ashing in a muffle furnace at about 550-600ºC till the residue become white. The percent of ash was calculated as follows: Percentage (%) of ash = (Weight of ash / Weight of Sample) × 100. TSS and pH estimation, Total soluble solid (TSS) content was determined by Abbe refractometer, ATAGO 9099, Japan by placing a drop of juice on its prism. Percent TSS obtained as Brix (unit of TSS) from direct reading of the refractometer. The pH of the samples was measured by digital pH meter of type H1 98106 by HANNA at ambient temperature. The sample was taken as juice. Ascorbic acid estimation - Ascorbic acid was determined by 2,6-dichloroindophenol titrimetric method. Briefly, Sample (2g) was homogenized with 3% metaphosphoric acid (25 ml) and was filtered through filter paper (Whatman 1, 7.0 cm). Then an aliquot (5 ml) of filtrate was titrated with the 2,6-dichloroindophenol dye (standardized by the metaphosphoric acid) to a pink end-point. Results were expressed on a fresh weight basis as mg ascorbic acid equivalent/ 100 g sample. Weight loss estimation - For physiological analysis weight loss was performed in spinach leaves. Water loss from the fresh leaves was measured by the change in weight of the samples over a storage period. The weight of produce was recorded immediately after treatment then daily during storage in the sealed polythene bags at 12°C for 12 days. Water loss was calculated from the formula: Weight loss = final weight – initial weight of sample / Initial weight (g) of sample X 100. Statistical analysis - Statistical procedures were performed using SPSS for Microsoft version 18.0 software package (SPSS Chicago, IL). To determine significant difference between treatments least significant difference (LSD) at P < 0.05 was used.

Source of Information: International Journal of Biosciences | IJB |; ISSN: 2220-6655 (Print) 2222-5234 (Online); Vol. 3, No. 5, p. 25-34, 2013

Article Link (Online Journal): http://www.innspub.net; doi: http://dx.doi.org/10.12692/ijb/3.5.25-34

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present results suggested that irradiation with 1.0 kGy have positive effect on the liking or overall acceptability, biochemistry and physiology of spinach even though irradiation promoted the loss of ascorbic acid during 12 days storage. Results also suggested that irradiation could be a promising technique to improve safety with minimal loss in quality of vegetables like spinach which is very effective in improving the overall quality and economical value of vegetables for developing countries like Bangladesh. For Food manufacturers, radiation technology can be useful as it can result in shelf life extension of different food produce, thereby, reducing post harvest spoilage losses.

Knowledge Management: Journal