Water sorption isotherm and glass transition temperature of freeze-dried Syzygium cumini fruit (jambolan)

Abstract

The sorption isotherms analysis and glass transition temperature should provide important information about the role of water in food. Sorption/desorption isotherms of freeze-dried jambolan (FDJ) were determined at 15, 25 and 35°C temperatures. The determination of glass transition temperature is also performed in order to establish packaging and storage conditions. The hygroscopic behavior of jambolan pulp after freeze-dried process was studied through sorption isotherms and models fit to experimental data. The freeze-dried material was highly hygroscopic and Peleg's model showed the highest coefficient of determination and lower values of average deviation and relative average error estimated, therefore the best fit sorption isotherms. The lowest value of monolayer was 7.64 gH 2 OÁ100g db -1 to 25°C. At temperature higher than 17°C (T g ), the material become more amorphous and the site of interaction with water molecules becomes available. As conclusion, the material must be storage at temperatures below T g and low relative humidity.

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“…mol −1 at 5% moisture to 0.27 kJ.mol −1 at 30%, thus approaching the heat of vaporization of pure water. The linear decreasing trend of q st was also observed by de Santana et al (2015) for freeze dried jamun pulp and by Basu et al (2013) for pectin. It may be worth mentioning that the maximum q st in this study is comparable with the value for orange juice powder (9.05 kJ.…”

“…At increased temperatures, water molecules because of their activation at higher energy levels gain higher mobility, become unstable and break away from the binding sites, thereby causing a reduction in EMC, as explained by Menkov and Durakova (2007). According to de Santana et al (2015) and , the water vapour pressure (WVP) on powder surfaces increases at higher temperatures, allowing the water molecules to get detached from the binding sites. Interestingly for a w higher than 0.75, the increase in EMC with a w is even higher than for the previously displayed regions.…”

“…Mathematical modelling enables generation of MSI at any unknown temperature within the temperature range for which the MSIs have already been developed empirically. de Santana et al (2015) reported MSIs of freeze dried jamun pulp (without skin) containing no additives. Biswal, Mohapatra, Panda, and Dash (2017) modelled the desorption isotherm of fresh jamun fruits.…”

Effect of composition and drying method on glass transition temperature, water sorption characteristics and surface morphology of newly designed β-lactoglobulin/retinyl palmitate/disaccharides systems

“…The calorimetric information from DSC can be directly used to understand the thermal transitions that the food system undergoes during processing or storage [13][14][15][16][17]. Modulated differential scanning calorimetry (MDSC) which is an enhancement to conventional DSC and involves the application of a sinusoidal heating or cooling signal to a sample and the subsequent measurement of the reversing and non-reversing components of the heat flow response is widely used technique for studying the glass transition [18][19][20][21].…”

Microwave‐convective hot airdried jamun (Syzygium cuminiL.) pulp powder: Optimization of drying aids

“…Jamun pulp is usually acidic (Ghosh, Pradhan, & Mishra, 2018;Santhalakshmy, Bosco, Francis, & Sabeena, 2015) and a rich reserve of reducing sugars such as fructose, galactose, glucose, maltose, and mannose (Kubola, Siriamornpun, & Meeso, 2011;Noomrio & Dahot, 1996). Except some stray information on moisture sorption/HG of freeze-dried jamun pulp (without skin; experimental details were not available) by de Santana et al (2015) and spray-dried jamun juice (Santhalakshmy et al, 2015), in none of the published literature (relating to jamun) this aspect was reported.…”