Effect of ultrasonic pretreatment on the rheology and structure of grass pea (Lathyrus sativus L.) protein emulsion gels induced by transglutaminase

In this study, emulsion gels were prepared by sonicated grass pea protein isolates (GPPI) at different ultrasonic amplitudes (25, 50 and 75 %) and times (5, 10 and 20 min). Formation of emulsion gels was induced by transglutaminase. Enzymatic gelation of emulsions stabilized by sonicated GPPI occurred in two stages. A relatively fast stage led to the formation of a weak gel which was followed by a slow stage that strongly reinforced the gel structure. Emulsion gels fabricated by sonicated GPPIs showed a homogeneous and uniform droplet distribution with higher elastic modulus compared to the native protein. A stiffer emulsion gel with a higher G' was formed after the protein was treated at 75 % amplitude for 10 min. After sonication of GPPI, the water holding capacity (WHC) of emulsion gels increased in accordance with the mechanical properties. Higher intermolecular cross-linking within the gel network increased the thermal stability of emulsion gels fabricated by sonicated GPPI. Although sonicated-GPPI emulsion gels clearly displayed homogenous microstructure in comparison to that made with native GPPI, the microstructures of these gels were nearly identical for all sonication amplitudes and times

The rheological properties of ketchup as a function of different hydrocolloids and temperature

The flow properties of ketchup were assessed upon addition of commonly used food thickeners: guar, xanthan and CMC gum at three different concentrations (0.5%, 0.75% and 1%) and four temperatures (25, 35, 45 and 55 °C). The ketchup without supplementation served as a control. All ketchup formulations exhibited non-Newtonian, pseudoplastic behaviour at all temperatures and hydrocolloid levels. The Power-law and Herschel-Buckley model were successfully applied to fit the shear stress versus shear rate data. The flow behaviour indices, n and n′, varied in the range of 0.189–0.228 and 0.216–0.263, respectively. The consistency coefficients, k and k′, were in the range of 8.42–27.22 and 6.56–20.10 Pa sn, respectively. The addition of hydrocolloids increased the yield point (τ0) and apparent viscosity of the ketchup in comparison to that of the control. The Arrhenius equation was successfully used to describe the effects of temperature on the apparent viscosity of the prepared formulations. The Ea value appeared in the range between 5492.6 and 21475.8 J mol−1

Use of quince seed mucilage edible films containing natural preservatives to enhance physico-chemical quality of rainbow trout fillets during cold storage

AbstractIn this study quality changes of rainbow trout fillet wrapped with quince seed mucilage QSM film incorporated with 0–2% (V/V) thyme or oregano essential oil, as natural preservatives, during storage of 18d at 4°C were investigated. The control and wrapped fillet samples were analyzed for texture, lipid oxidation, and color characteristics. After 6d of storage, a significantly increasing trend was observed for lipid oxidation in control samples. Peroxidation values (PV) varied for all treatments and remained lower than 8meq/kg throughout the storage time (18d). The lowest PV was obtained in fillets wrapped with QSM film containing 2% oregano essential oil. Compared to control samples, fillet samples wrapped with QSM films presented a significant reduction in pH after 12d (P<0.05). L* and b* color parameters were increased while parameter a* was decreased linearly for all treatments during the storage time