Physicochemical and microstructural characterisation of green gram and foxtail millet starch gels.

The starch and starch gels from green gram (GG) and foxtail millet (FM) were characterised for their physicochemical, thermal and microstructural characteristics; the features of shape and size were determined by image analysis. Both GG and FM formed well-set gels at 9% concentration of starch. The fracture strain of the gels was between 78 and 80% indicating non-brittle gels. The peak temperatures of the native flour of GG (74.9 °C) and FM (75.7 °C) were significantly higher than their corresponding starch samples (72.2 and 75.0 °C). The conclusion temperatures of the FM native flour (81.2 °C) and starch (79.4 °C) samples were higher than the native GG flour (79.9 °C) and GG starch (77.1 °C) samples. Starches were nearly spherical as the roundness values were between 0.88 and 0.95. Green gram starch was pentagonal having an average diameter of 3.9-9.2 µm while foxtail millet starch was spherical with a diameter of 4.9-10.1 µm. The freeze-dried GG and FM starch gels showed cellular structure containing organised hexagonal pores, bound by thin pore walls; the GG starch gels deviated from the circular shape as they had the highest elongation value of 4.21. The thicker pore walls were observed for GG starch gels (0.88 µm) compared to that of FM samples (0.57 µm). The higher pore wall thickness in the case of GG gel showed the formation of junction zones.

Textural characterization of foxtail millet gels: effect of cations and hydrocolloids.

Foxtail millet (Setaria italica) is traditionally cultivated in mainly dry land areas and has nutritional importance. The textural characteristics of gels, formed with foxtail millet flour at different concentrations (9-13 %, dry solid basis) along with selected cations and hydrocolloids, were determined. Different concentrations of monovalent (NaCl) and divalent (CaCl2 and FeSO4) cations, and hydrocolloids such as gelatin, gellan, starch, xanthan and agar were incorporated in gels. The gel forming ability markedly improved with an increase in the concentrations of CaCl2 and FeSO4, while NaCl had a marginal effect. Gels prepared with 11 % of foxtail millet alone were found to sensorially acceptable while addition of 0.5 % CaCl2 or 0.2 % FeSO4 respective with 10 % foxtail millet also resulted in acceptable gels. Among the hydrocolloids, starch and gellan had marked effects on gel formation, and textural and sensory attributes. The principal component analysis (PCA) plot showed that concentration of foxtail millet formed a cluster with sensory hardness, springiness, cohesiveness, and instrumental peak stress, fracture strain and compression energy indicating that these attributes were interrelated to each other. Stickiness and gelling time formed a cluster on the other side of the axis indicating inversely related. Foxtail millet has a good potential for development of new ranges of gelled health benefiting convenience products with nutraceutical property, and the addition of cations helps to achieve acceptable structural integrity.

Jilebi 3: Effect of frying conditions on physical characteristics.

The process of jilebi making includes the frying of specially shaped batter strands to obtain a crisp texture followed by absorption of sugar syrup. The effects of frying temperature (150-180 °C) and time (15-300 s) on the physical characteristics have been investigated; these are moisture and fat contents, density, colour, textural attributes and microstructure. Among the textural parameters obtained by shearing the jilebi strands, shear failure force and the number of minor fractures increase markedly with an increase in time of frying. The brightness of the sample is lower when fried at higher temperatures like 180 °C compared to that of 150 °C; the hue or dominant wavelength of batter prior to frying is 578.0 nm, and after frying, it is between 564.8 and 591.3 nm indicating an overall shift towards yellow colouration during frying. The density of the jilebi strands decreases along with moisture content, while fat content increases gradually with an increase in frying time. The microstructure and image analysis of the fried products indicate the creation of porous structure consisting of several pores that are separated by thin cell walls of thickness between 10 and 15 µm. The eccentricity of pores/vacuoles in jilebi is between 0 and 0.92 indicating a close resemblance to elliptical shapes. The samples fried at 160 °C for 180-240 s have been judged as the best sample both as fried and fried-sugar syrup soaked products.