Studies on the effect of Microwave heating on Guava (Psidium guajava L.,).

Nawghare, Gajendra. K (2014) Studies on the effect of Microwave heating on Guava (Psidium guajava L.,). [Student Project Report] (Submitted)

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Abstract

Guava is a commercial fruit crop in many tropical and sub-tropical countries of the world. The fruit is a rich source of vitamins, minerals, fibre and dietary antioxidants. High perishability and susceptibility to physical damage, chilling injury, diseases and insect-pests are the major postharvest constraints of guava fruit. This chapter reviews the economic importance, postharvest physiology, maturity indices and effects of pre- and postharvest factors on guava fruit quality. Postharvest diseases, disorders and phytosanitary treatments are also reviewed. The chapter then discusses the harvest and postharvest handling procedures and methods of ripening and senescence control. The processing of guava fruit into fresh-cut and other processed products is also described. An experimental investigation was carried out with three different blanching methods by using microwave (MW) heating system. Due to microwave blanching Guava exposed at 900w power scale at different wattage level. The objective of this study was to employ microwave blanching (instead of conventional blanching) during blanching and investigate its effect on proximate content and quality attributes (texture, colour, proximate content) of Guava. Guava was blanched with 1.conventional blanching 2. Microwave exposed hot water blanching 3. Microwave heating at 900w power scale with different wattage. In each method guava slices were treated with 1,2,3 min time duration at 70°,80°,90°c temperature . In microwave heating 2w/g, 3w/g, 4w/g, 5w/g for 1, 2, 3 min on 900w power scale. after each blanching process quality characteristics (pH, ˚°Brix, total acidity, reducing sugars, colour, minerals, microbial flora, pectinmethylesterase (PME) activity, PPO activity ,POD activities) of blanched Guava were investigated All the proximate analysed, texture, colour were analysed and compared with fresh and other treated guavas. Colour measurement was done by digital hunter lab analysis, Texture Analyzer was used for texture measurement and oil content was determined using Soxhlet method. The second part of the study was the microwave drying. Differently blanched Guava was dried for the purpose of the study drying model. Guava was exposed at 900w power scale for 30 sec on 30 sec off microwave exposing technique. Conventional blanching of 70oC 3 min and 80oC 1 min has shown the hardness as 35 % compared to fresh. There is an effect of microwave heating on texture of guava showing xiv softness. There was increase in lightness value of color by microwave blanching, but in other treatments not much variance in L*, a* and b* values was found when compared to the fresh. The optimized microwave blanching at 2 W/gm for 1 min shown the proximate composition similar to fresh. 99.3% of inhibition of PME activity was found in 5 W/gm for 3 min of microwave blanching. 100 % of inhibition of POD activity was found in conventional blanching 90oC 3 min; conventional followed by MW 90oC 2 min and MW heating 5 W/gm for 2 min. Higher moisture removal rate was found in MW heating directly irradiated at 5 W/gm for 1 min. Out of 11 optimum drying models, for tray drying “Modified page model” was found to have a constant of a= 0.9778, k= 7.5306, n= 1.3115 R2= 0.9984 for fresh .,Weibull distribution was found to have a constant of a= 0.1381, b= 1.1198, k= 0.0108, n= 1.5549 R2= 0.9986 for conventional blanching 80oC 2 min., “Modified Henderson model and Pabis model ” was found to have a constant of a= 81.7445., b= -125.9763,c=45.2318 k= 0.024, g= 0.02, h1= 0.0332 , R2= 0.9994 for Conventional followed MW at 80oC 2 min , Weibull distribution was found to have a constant of a= -0.032, b= 1.0292, k= 0.0689, n= 1.6273 R2= 0.9996 for microwave blanching at 5 W/gm 1 min .Hue and chrome values of conventional blanching of 70oC 1 min, conventional followed by MW blanching 70oC 3 min, MW dried samples of 4 W/gm 2 min were near to the fresh values. The work carried out for blanching and drying of guava optimized for proximate analysis, colour values, enzyme inactivation and drying was found to have an insignificant variation by using MW blanching and drying except for hardness. So it was found that there is an effect of microwave heating on blanching and the drying rate will be faster when compared to conventional and conventional followed by MW drying.

Item Type:	Student Project Report
Uncontrolled Keywords:	Guava, blanching methods, microwave (MW) heating system
Subjects:	600 Technology > 08 Food technology > 24 Fruits 600 Technology > 08 Food technology > 06 Preservation and Storage > 05 Microwave heating
Divisions:	CFTRI Resource Centres > Hyderabad
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	23 Jun 2015 07:29
Last Modified:	23 Jun 2015 07:29
URI:	http://ir.cftri.res.in/id/eprint/11869

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