Understanding, characterization and nutrient bioaccessibility of specialty food gels for health benefits

Shipra, Tiwari (2015) Understanding, characterization and nutrient bioaccessibility of specialty food gels for health benefits. PhD thesis, University of Mysore.

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Abstract

The influence of cations like CaCl2 (0.05 and 0.1%) and FeSO4 (0.05 and 0.1%) on the rheological properties (apparent viscosity, zero shear viscosity and relaxation time) of 1% gellan sol prior to gelling was investigated. The apparent viscosity, reported at a shear rate of 100 s-1, indicated that the gellan dispersions without any cation possessed lower apparent viscosity compared to other samples containing different cations. Gellan, agar and their combination (1:1, 2 g/100 g) gels as model systems were subjected to strains up to 0.8 to determine several textural characteristics (rigidity constant, degree of concavity, Young’s modulus and apparent biaxial elongational viscosity, be) and the fracture characteristics. However, the fracture strain for gellan was highest followed by agar and agar-gellan gels exhibiting high brittleness in agar/agar-gellan gels but toughness in gellan samples. Gellan gels are suitable to prepare chewable fabricated juicy gels, while brittle products resulted from agar/agar-gellan. It is proposed that be is a good index for characterising the rheological status for gels in relation to product development and compressionspreading. Studies were carried out to develop nutritious gels using gellan gum (1-2%, w/w), mango pulp (0-40%), sugar (0-20%) and ferrous sulphate (0-0.10%). In addition, flaxseed powder (0-10%) and whey protein concentrate (0-5%) were incorporated to selected gel samples. The loss modulus of sols was mostly affected by mango pulp. The fracture force varied widely between 0.5 and 93.5 N indicating the formation of very soft-brittle to tough products. Mango pulp had a major linear effect on the fracture force of the gels followed by the concentration of FeSO4. Mango pulp and/or sugar contents increased the firmness of the gels. The principal component analysis indicated that sugar had a strong correlation with fracture strain and sensory springiness. These results are useful for developing chewy/springy fabricated gels that xvii can be achieved with a high level of sugar. The characteristics of moisture removal and selected physical properties during the dehumidifier assisted drying of model food gel systems like agar and gellan gels were studied. The effect of gel forming ingredients and nutrients like FeSO4, whey protein concentrate (WPC) and flaxseed powder (FSP) were investigated with an overall aim of developing a delivery system for nutrients as a convenience food gel. Gellan and agar gels were prepared at concentrations of 1, 2, and 3% (w/w) and subjected to drying at a low temperature of 40oC in a dehumidifier-assisted dryer up to 12 h. The different quality parameters that were determined included the extent of shrinkage, moisture content, textural parameters and the diffusion coefficient. Agar gels possessed higher moisture ratios compared to corresponding gellan samples. The gellan gels were much harder than the corresponding agar gels. The addition of WPC, FeSO4 and flaxseed increased the textural indices like fracture force, fracture strain, fracture energy and total energy for 80% compression for all the gels. The indices computed for the dried agar and gellan gels were the maximum and minimum dimensions of air cells, area and perimeter of cells, and the thickness of cell walls. Based on these primary data, other derived indices such as roundness, equivalent diameter, elongation and compactness were computed. Rehydration of dried material resulted in the increase of both mass and volume of samples. Rehydration was affected by the drying time of the gels. Gel samples dried for 1 h showed higher extent of rehydration of 85.7% and 95.9% after 15 and 240 min of rehydration at room temperature, respectively. Comparisons were made between non-aerated and aerated gel samples. Highest fracture strain (24.1%) was achieved when the level of WPC was highest (3%) with no added sucrose and mango pulp for both non-aerated and aerated gels. Highly opaque gels resulted from the inclusion of air. The opacity was high (95.8%) for the aerated gels compared to the corresponding non-aerated gels (90.4%). Transparent gels with the opacity of less than 4% were formed when sucrose level was high (30%). The density of the aerated gels were lower than those for the nonaerated samples (1000.3, 899.9 and 866.8 kgm-3 for non-aerated, and gels aerated for xviii 30 and 60 s, respectively). A four-layered neural network structure of 4–6-8–6 relating the variations in the ingredients used for gel formation and physico-chemical attributes of non-aerated and aerated gels has been developed. The bioaccessibility of selected gels was examined due to the inclusion of ferrous sulphate as the sources of iron. The iron content of the gels ranged from 5.22 mg/100g to 12.63 mg/100g in samples. It is inferred that micronutrient enriched gels can serve as an attractive convenience food to combat micronutrient deficiencies. The present study concludes that gels can be a good medium to offer convenience to consumers as attractive foods. The health benefiting nutrients can also be supplied through gels in addition to incorporating air to reduce the energy intake.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	nutritious gels, gellan gum, mango pulp, health benefits, nutrients
Subjects:	600 Technology > 01 Medical sciences > 13 Nutrition-Human 600 Technology > 08 Food technology > 31 Food Additives
Divisions:	Food Engineering
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	19 May 2016 07:34
Last Modified:	19 May 2016 07:34
URI:	http://ir.cftri.res.in/id/eprint/12178

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