Influence of Wheat Starch, Cornstarch and Waxy cornstarch Treated with High Hydrostatic Pressure as Fat Replacers on the Characteristics of low fat Model Oil in Water Emulsion

Student: Ali Heydari

Supervisor: Seyed Mohammad Ali Razavi

Status: Current

Consumption of high dietary fat and many diseases, including obesity, diabetes, cardiovascular diseases, and cancer, are interdependent. The increasing demand and changing in human’s lifestyle for consuming low-fat products persuade food scientists and technologist to find and develop the low-fat food products. It is common knowledge that many foods, pharmaceuticals, biological fluids, and agrochemicals are categorized as emulsions. HHP process by changing in the physical and structural attributes of starches, creates more creamy texture with extended storage stability than the thermally modified starches, which is very practical for using HHP-treated starches as fat replacers. So, the impact of various concentrations of native starches as fat substitutes on the physical, rheological, and textural properties and stability of reduced-fat O/W model emulsions at different fat reduction levels was elaborated and compared with the full-fat emulsion.

Biopolymers identification and clustering based on rheological, thermal, and structural properties

Student: Ali Alghooneh

Supervisor: Seyed Mohammad Ali Razavi

Advisior: Stefan Kasapis

Status: Finished

In this study, the similarity of commercial gelling hydrocolloids (agar (AG), κ-carrageenan (κ-Car), alginate (ALG) and high methoxylated pectin (HMP)) and thickening hydrocolloids (carboxymethylcellulose (CMC), xanthan (XG), guar (GG)) with local hydrocolloids (basil seed gum (BSG), sage seed gum (SSG), balangu-shirazi seed gum (BSSG) and cress seed gum (CSG) were investigated, from the rheological, thermal, structural and microstructure properties points of view, using Fuzzy-clustering procedure. The rheological study of all hydrocolloids was performed on 1% gum concentration at 25 oC and totally 74 parameters were generated. Results showed that, all the rheological properties could be classified into seven fundamental properties of number of linkage, strength of linkage, distance of linkage, rupture and flow, rate of destruction, the extent of destruction, and the state of destructured samples. Clustering showed that HMP and XG could be substituted by BSG and SSG, respectively, CMC and GG could be replaced by CSG, and ALG could be replaced by BSSG. All the hydrocolloids showed 5, 5 and 4 different concentration, thermal and frequency patterns, respectively. ALG, BSSG, CSG, GG, CMC obeyed the time-temperature superposition theory; AG, κ-Car, HMP, XG, BSG and SSG followed the concentration-time superposition theory and ALG, BSSG, CSG, XG, BSG and SSG followed the strain-rate frequency superposition. Novel time of shearing -Strain rate superposition theory, classified all the hydrocolloids into 6 different groups. The puncture test showed that AG got the greatest hardness and consistency, κ-Car showed the highest elastic modulus and fracturability, and ALG showed the highest adhesiveness. Beyond the linear region, for the elastic component of all hydrocolloids the strain thickening behavior (S>0) and for their viscose behavior, shear thing behavior ( T<0) were observed. Clustering showed that, based on mechanical properties under large strains, XG can be replaced with BSG and SSG, while ALG, CMC and GG could be substituted with BSSG and CSG. Thermogravimetric analysis proved that all the studied hydrocolloids had three critical regions. Pyrolysis was ended in the ranges of 337.70 to 384.04 oC for CSG, BSG, ALG, CMC, 406.03-439.69 oC for SSG, BSSG, κ-Car and HMP and 507.00 oC for AG. Furthermore, the total weight loss of all hydrocolloids were in the range of 1.63-3.24 mg at the end of pyrolysis. Clustering showed that, based on thermal properties, GG can be replaced with BSSG and CSG, CMC can be replaced with SSG and ALG can be replaced with BSG. From the thermodynamic point of view, all the hydrocolloids showed three thermal peaks. Thermodynamic parameters at first ascending entropy (ΔS>0), while two other peaks showed exothermic (ΔH<0) and spontaneous (ΔG<0) reactions with ascending entropy (ΔS>0). Clustering of hydrocolloids based on FTIR results, showed that cellulosic hydrocolloids were grouped in the first cluster, hydrocolloids with uronic acid were in the second cluster, sulphated hydrocolloids were in the third cluster, galactomannan hydrocolloids were in the fourth cluster and branched hydrocolloids were in the fifth cluster. Microstructure analysis showed that AG, κ-Car and HMP have the Gaussian-Lorentzian distribution pattern of particle size, while this was weibull distribution pattern for ALG, XG, BSG, SSG, CSG and BSSG, and normal logarithm distribution pattern for GG and CMC. Furthermore, there was a good correlation between the extent of network recovery in thixotropy test and particle size of hydrocolloids (R2=0.91). Generally, this research suggested novel hydrocolloids as an appropriate substitute for commercial ones in food formulation.

Effect of Cornstarch Nanocrystal as Fat replacer on Characteristics of Model Oil in Water Emulsion

Student: Fatemeh Javidi

Supervisor: Seyed Mohammad Ali Razavi

Advisior: Asad mohammad amini

Status: Finished

The objective of this study was to evaluate cornstarch nanocrystals (CSNC) suspensions (10, 12 and 14%) as a fat replacer in reduced fat emulsions (25, 50 and 75% fat reduced) and optimization of the fat reduced formulations. In this regard, CSNC characteristics including particle size (48 nm), zeta potential (-34.6 mV) and Sulfate content (0.21%) were determined. In addition, crystallinity and water binding capacity (36.6% and 320%, respectively) were more than those of source starch (28% and 89%). Then, in comparison with full-fat emulsion (control; 80% fat), rheological and physical properties of the reduced fat samples were evaluated. The results showed that increasing fat replacement level from 25 to 75% and CSNC concentration from 10 to 14% decreased droplet size from 325 to 58 nm and increased zeta potential from -33.2 to -39.4 mV which provided more interaction surface and inter-molecular interactions. So, the increasing trend in some linear viscoelastic properties such as the yield stress from 0.16 to 7.45 Pa was a representative of increased structural strength and enhanced gel-like behavior. On the other hand, although the spreadability index of the control sample was 1.36, it was increased from 1.34 to 3.71 as a result of fat reduction and CSNC addition. This observation was related to the more complex and fragile network of the emulsion in the nonlinear viscoelastic region and was in accordance with large deformation rheological properties, for instance, flow behavior index, thixotropy rate and time constant of Cross model. In addition, no creaming was observed for all the reduced fat and full-fat samples after 6-months storage. Numerical optimization also determined optimum formulation of the reduced fat emulsion based on the properties of a full-fat emulsion (control; 80% fat) as being the fat replacement of 47.80% and CSNC concentration of 11.99%. In the end, the full fat and optimum reduced fat emulsions were stored at 4ᵒC a month at which their droplet size increased from 144 to 496 nm and from 149 to 234 nm, respectively. However, both samples were stable with regard to creaming. Furthermore, there was a significant reinforcing effect of storage time on the emulsions network structure, which was different between the control (15th day) and optimum (29th day) samples due to their different formulations.

Characterization of Structural, Physical and Thermal Properties of Sage Seed Gum-Laponite and Titanium Dioxide Nano-Bio Aerogels

Student: Seyed Amir Oleyaei

Supervisor: Seyed Mohammad Ali Razavi

Advisior: Kirsi Susanna Mikkonen

Status: Finished

In this work, an extensive study was carried out regarding to the preparation and characterization of sage seed gum (SSG) based aerogels as substituted for synthetic polymer foam for food packaging materials. At first, the physico-chemical and rheo-mechanical properties of SSG hydrogel, reinforced by various ratios (0-25 wt.%) of Laponite and TiO2, were investigated. Particles size measurements indicated the formation of large SSG-Laponite and -TiO2 microstructures upon nanoparticle adding, due to the interactions generated between the anionic SSG and the charged surfaces of nanoparticles. Laponite and TiO2 affected the surface tension and density of the SSG-based systems significantly, but only TiO2 influenced the ζ-potential. The dynamic rheological behavior of SSG-based nanocomposites reflected the reinforcing effect of secondary structures and percolated three-dimensional network, suggested a structural modification of the hydrogels with the Laponite and TiO2 loading. An improvement in texture profile analysis parameters was observed in Laponite and TiO2 content ≤5 wt.% and ≤15 wt.%, respectively. For nanoparticles ˃5 wt.% Laponite and 15 wt.% TiO2, a significant decrease was obtained. Deformation of rod-like junction zones acting as physical crosslinks in the system and fracture theory were used to explain the strain-stiffening and adhesive behavior of SSG-based gels, respectively. In conclusion, Laponite and TiO2 improved the rheological and physico-chemical properties of SSG-based hydrogel and extended its potential as promising future bio-products for industrial applications. The nanobioaerogel preparation stage was performed via frees-casting route followed by lyophilization. The goal of this stage was to improve the functional properties of SSG matrix as well as reducing the bubble sizes to prepare nanofoams in order to enhance mechanical and thermal insulation performance. Several methods were used to characterize the prepared foam materials including filed emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), BET Specific surface area and BJH pore size, Fourier transform infrared (FT-IR) spectroscopy, Differential Scanning Calorimetry (DSC), thermogravimetric analyses (TGA), thermal conductivity, mechanical and water-sensitivity properties, density and color analyses. The obtained results indicated that the presence of nanoclay and TiO2 till a critical concentration in SSG matrix caused more uniformity in the structure of the aerogels. Also, increasing of nanoparticles content resulted in higher density, compressive strength, and young modulus. The results of thermal conductivity and morphology revealed that presence of Laponite and TiO2 improved thermal insulating properties due to reduction of average cell size. Moreover, we found that the chchemical vapor deposition (CVD) of TEOS has a dramatic influence on the water-sensitivity of SSG based aerogels. The use of CVD-TEOS increased the water contact angle of material and decreased water solubility and moisture absorption. The achievements from this study suggested that the prepared SSG based nanobioaerogels can be a potential alternative to commercial synthetic foams for packing food products.

Investigation of physicochemical and rheological properties of native and Hydrothermally modified acorn (Quercus brantii Lindle.) starch

Student: Hooman molavi

Supervisor: Seyed Mohammad Ali Razavi

Advisior: Reza  Farhoosh

Status: Finished

       In this research physicochemical and rheological properties of native and hydrothermally modified acorn starches were investigated. The results showed that native acorn starch owned high purity and the granules were mainly elliptical and spherical with the mean diameter of 7.32 μm. Hydrothermal modifications slightly changed the morphology. The solubility, swelling properties and amylose leaching of acorn starch were mostly influenced by Heat-moisture treatment (HMT). XRD pattern of native starch (C-type) did not change on hydrothermal modifications, but native and annealing (ANN) modified starches showed the most crystallinity. DSC results showed that the gelatinization temperatures and enthalpy of native starch were 59.9, 71.3, and 80.6 °C and −14.9 mJ/mg, respectively, and hydrothermal treatments generally increased the gelatinization temperatures. Regarding to RVA results, peak, breakdown, trough, setback, and final viscosities of native starch were 415, 143, 272, 168, and 440 RVU, respectively, and viscosity parameters of native starch were mainly more than those of hydrothermally modified starches. Generally, the intensity of the effects of hydrothermal modifications followed the order: HMT > dual modifications > ANN. The steady state rheological data of starch dispersions were fitted to the power law (R2=0.769–0.980) and Casson models (R2=0.904–0.994). According to the power law model, all native and hydrothermally modified starches presented shear-thinning behavior with the flow behavior index between 0.697 and 0.933. The consistency coefficient (k) and apparent viscosity (ηa,100) of starches were in the range of 3.157–246.167 mPa sn and 2.212–74.443 mPa s, respectively. Based on the Casson model, the plastic viscosity (ηc) and yield stress (τ0c) of starches were in the range of 1.977–41.167 mPa s and 0.333–506.667 mPa, respectively. All rheological parameters, except for the flow behavior index, increased with increasing in concentration, and decreased with temperature. The temperature dependency of all the starches was well described by the Arrhenius model (R2=0.837–0.999). The activation energy (Ea) values were in the range of 4.47–12.96 kJ mol-1. The concentration dependency of all the starches in the temperature range of 25–70 °C was well fitted to the power law (R2=0.919–0.998) and exponential (R2=0.970–0.999) models. Generally, the rheological parameters such as k, ηa,100, ηc, and τ0c of native starch were maximum and those of ANN starch were between those of native and HMT starches. These properties for dually modified starches were between those of single ones, showing that the second treatment could negate the effects of the first one. Regarding to dynamic rheological data, native starch presented the greatest values obtained by amplitude sweep test followed by annealed starch whilst heat-moisture treated starch outlined the minimum values. The values for dually modified starches were between those of single modifications. Loss tangent values at linear viscoelastic region were in the range of 0.03-0.06, demonstrating the dominance of elastic behavior of native and modified starch dispersions. The magnitudes of storage modulus (G’) were greater than those of loss modulus (G”) over the frequency range (0.63–62.8 rad s-1). Native starch presented the most loss tangent values (tan d) at 6.28 rad s-1, while HMT-treated starches showed the least ones. The ability of gel forming reduced slightly in hydrothermal treatments. The hardness, adhesiveness, cohesiveness, springiness index, gumminess, and chewiness index of acorn starch were 261.3 g, 0.64 mJ, 0.96, 0.98, 252.1 g, and 248.0 g, respectively. Among different hydrothermal treatments, ANN did not alter the textural parameters of native starch significantly.

Interactions and gelation of Lathyrus sativa protein isolated and Lepidium perfoliatum seed gum for emulsion-gel preparation

Student: Mohammad Ali Hesarinejad

Supervisors: Arash Koocheki, Seyed Mohammad Ali Razavi

Advisior: Mohammad amin mohammadifar

Status: Finished

The purpose of the present study is producing a low-fat and stable emulsion gel based on Lathyrus sativus protein isolate (LSPI). To achieving this goal, the project was carried out in three parts: after examining the effects of various concentrations of calcium chloride and transglutaminase enzyme on the characteristics of cold gel protein isolated and optimizing its conditions, the rheological, thextural, thermal and microstructural properties of the LSPI – Lepidium sativum seed gum (LPSG) mixed gels were investigated. Finally, the effect of different oil ratios on the characteristics of emulsion gel based on the LPSG-LSPI mixture induced by transglutaminase (TGase) was investigated with the aim of producing low-fat and stable emulsion gel. In the first section, it was found that LSPI can be recognized as an effective ingredient for the production of cold-gels induced by TGase and can be used to produce new functional structures in food production processes. The results showed that optimum condition of LSPI gelation was observed at protein content of 9.92% and TGase of 10 U/g which had the maximum gel stiffness and minimum turbidity, syneresis and tanδ. The results of protein-gum interactions showed that the formation of a complex between protein and gum in aqueous medium is highly dependent on different ratios of protein-polysaccharide. Rheological behavior and FTIR of mixed systems showed no connection between two biopolymers. The results of the emulsion gel system showed that increasing gum concentration increased the elastic and viscous modulus in the emulsion gel. It has also been shown that the emulsion gel produced on the basis of LSPI induced by transglutaminase, provides a weak gel behavior. Comparison of the images obtained from SEM also showed that samples with more LPSG content have more continuous and more consistent networking. Also, the water holding capacity in the gel emulsion system increased with increasing gum concentration.