Suvendu Bhattacharya

Hydrocolloids as thickening and gelling agents in food: a critical review

Hydrocolloids are widely used in many food formulations to improve quality attributes and shelf-life. The two main uses are as thickening and gelling agents. As thickening agents, they find uses in soups, gravies, salad dressings, sauces and toppings while as gelling agents, they are extensively used in products like jam, jelly, marmalade, restructured foods and low sugar/calorie gels. The role of specific hydrocolloids for thickening and for gel formation is reviewed pinpointing specific applications in food formulations and for product development.

Food Gels: Gelling Process and New Applications

Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like hydrogen bonds, electrostatic forces, Van der Waals forces, and hydrophobic interactions. Polysaccharides including hydrocolloids are strongly hydrated in aqueous medium but they tend to have less ordered structures. The mechanism of gelation depends on the nature of the gelling agent(s) and on the conditions of gel formation like the temperature, the presence of ions, the pH, and the concentration of gelling agents, etc. Characterization of gels can be performed in several ways of which rheological measurements are frequently practiced. Multi-component or mixed gel system is an important area of interest in which two or more gelling components are simultaneously used to achieve certain specific structural and functional characteristics. We here discuss about the different gels and gelling agents, the characterization of gels, and the mechanism of gelation with an emphasis on mixed or multi-component gels that would have significant commercial applications.

Agglomeration of Food Powder and Applications

Agglomeration has many applications in food processing and major applications include easy flow table salt, dispersible milk powder and soup mix, instant chocolate mix, beverage powder, compacted cubes for nutritional-intervention program, health bars using expanded/puffed cereals, etc. The main purpose of agglomeration is to improve certain physical properties of food powders such as bulk density, flowability, dispersability, and stability. Agglomerated products are easy to use by the consumers and hence are preferred over the traditional non-agglomerated products that are usually non-flowable in nature. The properties of food agglomerates and the process of agglomeration like employing pressure, extrusion, rewetting, spray-bed drying, steam jet, heat/sintering, and binders have been reviewed. The physical and instant properties of agglomerated food products have also been discussed.

Turmeric Powder and Starch: Selected Physical, Physicochemical, and Microstructural Properties

UNLABELLEDnTurmeric powder and its starch were characterized for physical, physicochemical, and microstructural characteristics. X-ray diffractogram indicated that turmeric starch to be of B type. Dried and cured-dried turmeric powder samples showed higher water-holding capacity (3.62 and 4.78 g/g, respectively) compared to isolated starch (1.07 g/g) at 30 °C. Non-Newtonian shear-thinning characteristics were observed with turmeric powder dispersion containing 10% (w/w) solids. A power law model fitted well to correlate the shear-rate and shear-stress data (r= 0.993 to 0.999, P≤ 0.01) for both samples. Apparent viscosities of isolated turmeric starch and cured-dried turmeric powder dispersion containing 10% (w/w) solids were 1.29 ± 0.03 and 7.57 ± 0.39 mPa s, respectively. Microstructure of starch particles showed a smooth flat outer surface. The approximate length and breadth of isolated elliptical starches were 25 and 10 μm while the thickness was about 5 μm.nnnPRACTICAL APPLICATIONnIsolation and characterization of starch from an unconventional source like turmeric rhizome indicate a potential application as a functional ingredient in foods and pharmaceutical industries including agglomerated products.

Dehumidifier assisted drying of a model fruit pulp-based gel and sensory attributes.

UNLABELLEDnModel fruit pulp-based gels were prepared by varying mango pulp (0% to 50%), sucrose (0% to 20%), and agar (1% to 3%) and according to a response surface experimental design followed by drying at a low temperature of 40 °C upto 15 h in a tray dryer assisted by a dehumidifier. The moisture content, shrinkage (SHR), and rheological parameters (failure strain, failure stress (FS), firmness, and energy for compression) were determined as a function of drying time. The composition of gel, particularly the agar content had a prominent effect on the characteristics of the dried gel. Detailed descriptive sensory analysis employing principle component analysis (PCA) biplot indicated two distinct groups of attributes; the first group comprised initial and final moisture contents, extent of moisture removal (EMR), and shrinkage. The fracture stress and energy formed the second group. The analysis of variance for failure stress showed that it depended only on the positive linear and quadratic effects of agar (significant at P ≤ 0.01 and 0.05, respectively). The theoretically predicted extent of moisture removal at 95.6% could be achieved when the level of agar was 1.2%; pulp and sucrose levels were also close to their lowest levels of 3.6% and 0.04%, respectively.nnnPRACTICAL APPLICATIONnScope exists to develop gel-based fruit analogues wherein an appropriate hydrocolloid can be employed along with fruit juice/pulp. To provide a reasonable shelf-life of the developed intermediate moisture containing product, dehumidifier assisted drying is a pragmatic approach that affects sensory and rheological attributes of the dried fruit analogue.

Mangosteen Oil-In-Water Emulsions: Rheology, Creaming, and Microstructural Characteristics during Storage

The rheological properties and physical stability of mangosteen (Garcinia mangostana L.) extract in oil-in-water (MIO/W) emulsions were investigated. Rheological study on the emulsions exhibited Newtonian flow behavior. The 20xa0wt.% emulsion showed higher apparent viscosity than 10xa0wt.% MIO/W sample. The effects of salt (NaCl) concentration (0, 50, 100, and 200xa0mM) and heat treatment (70xa0°C) on the stability of the emulsions were also examined. Heat (70xa0°C)- and NaCl (100 and 200xa0mM)-treated emulsions showed creaming and droplet aggregation on storage for a period of 60xa0days. The 10xa0wt.% MIO/W emulsions stored at 4xa0°C showed a homogeneous distribution of oil droplets with good stability to creaming and viscosity independent of shear stress (i.e., a Newtonian liquid).

Roasting green coffee beans using spouted bed roaster: changes in physical characteristics.

Pea-berry grade of green coffee (Coffea arabica) beans were roasted in a laboratory model spouted bed roaster at different temperatures (150–250°C) and times (30–300xa0s). The roasted samples were analysed for instrumental colour (hue, chroma and brightness) and texture. Brightness of the roasted samples varied between 5.2 and 20.4%, and time of roasting markedly decreased the brightness values. The chroma showed a curvilinear decrease with both time and temperature of roasting; the lowest values were with highest roasting times and temperatures. The hue or dominant wavelength increased from 576 to 603xa0nm due to roasting. The maximum force offered by the roasted beans decreased with temperature and/or time of roasting. An appropriate condition for spouted bed roasting of green coffee beans was obtained considering colour of samples and desirable low failure/fracture force.

Mango pulp-agar based model gel: textural characterisation

The textural properties of a model gel system have been investigated by employing an experimental design concerning the effect of agar (1–3%), mango pulp (0–50%) and sugar (0–20%). A gel characterization method, based on the principle of penetration-shearing, has been applied to determine the response functions (fracture strain, fracture stress, energy for penetration-shearing and firmness). These textural indices can be fitted well (0.858u2009≤u2009ru2009≤u20090.953, pu2009≤u20090.01) to second order polynomials. Agar possesses the maximum effect and an increase in agar content markedly increases these indices while sugar imparts mostly a curvilinear effect; a failure strain as high as 33% has been achieved by increasing the agar content. The individual optimization (maximization), based on canonical analysis, on these indices indicates that agar content to be more than 2.8%. Gels with extensively varying textural properties can be achieved by changing the proportions of these ingredients.

Jilebi 2: Flowability, pourability and pH of batter as affected by fermentation

Fermentation of batter is an integral part of the preparation of jilebi, a traditional ready-to-eat sweet product of Indian sub-continent. The flowability and pourability of batter are crucial for forming jilebi strands during frying. Flowability and pourability have been determined from simulation studies based on the movement of batter on an inclined surface and the exit from an orifice, respectively; simple gadgets have been designed to determine these two characteristics along with providing the definitions. Response surface experimental design consisting of moisture content (50–65%), amount of added curd (0–10%) and time of fermentation (0–24xa0h) has been employed. The response functions are pH, flowability and pourability. Strong interaction effects of added curd and time of fermentation on the response functions have been observed. An increase in added curd and time of fermentation decreases pH in a curvilinear manner as both linear and quadratic effects are significant (pu2009≤u20090.01). Moisture content has a non-significant effect on pH but markedly affects the flowability and pourability of batter. Flowability and pourability decreases when there is an increase in consistency index or apparent viscosity.

Management of Polycystic Ovary Syndrome in India

Polycystic Ovary Syndrome (PCOS) is one of the most common endocrinopathy affecting women.[1] It has an unknown etiology and is recognized as a heterogeneous disorder that results in overproduction of androgens, primarily from the ovary, and is associated with insulin resistance (IR).[1] The Rotterdam 2003 criteria defines PCOS as incidence of any two of the three key criteria, namely, oligoovulation and/or anovulation, excess androgen activity and polycystic ovaries(PCO).[1,2] However, the terminology used in the context of PCOS needs to be revisited to reflect the actual clinical nature of PCOS.