نشریه پژوهش های علوم و صنایع غذایی ایران
سال دهم شماره 4 (پیاپی 30، زمستان 1393)

The objective of this study was the evaluation of pH، Color parameters [lightness (L*)، redness (a*)، yellowness (b*)، chroma (C*)، hue (H*)، a*/b* ratio، and color differences (ΔE)]، Mb، MetMb، OxyMb، DeoMb and WHC in minced meat. Three types of meat (Beef، camel and ostrich) and four mincing processes (three using a grinder with 7. 5، 4 and 3 mm diameter holes in the plate، and a fourth in which a cutter was used to obtain a finely minced product) were studied. The intact meat was used as the control. Significant differences were observed in the pH، Color parameters [lightness (L*)، redness (a*)، yellowness (b*)، chroma (C*)، hue (H*)، a*/b* ratio، Mb، MetMb، DeoMb and WHC of various types of meat (P 0. 05). WHC and chroma showed statistically significant differences (P 0. 05) for the mincing treatment. The ΔE and OxyMb showed no significant differences (p>. 0. 05) for mincing and also in meat types. High correlation between pH and L* (R2=0. 999)، pH and WHC (R2=0. 997) confirms the decrease in L* and increase in WHC along with increase in pH.

In this study، variations of the pasting properties، swelling power and solubility of two rice starches، low amylose (8. 7%) and high amylose (26%) at two citric acid concentrations (0 and 0. 01 M) was investigated. The results showed that the peak viscosity and breakdown viscosity of rice starch decreased significantly.

An accelerated shelf-life test using elevated temperatures 62، 72 and 82 C was conducted to predict the oxidation progression of walnuts over a long-term storage. Oxidation parameters including values of conjugated dienes (CD) and trienes (CT) values and thiobarbituric acid (TBA) value were employed to evaluate the oxidation processes. Changes followed an apparent first-order kinetic. Walnuts and walnut kernels were also kept in normal condition (20-30 С; RH، 35-45%) for 12 months in order to validate the approach. A maximum of energy (62. 24-75. 67 kJ mol-1 K-1) needed for formation of primary oxidation products and a minimum of energy (35. 65 kJ mol-1 K-1) to generate secondary oxidation products were calculated. Formation of oxidation products in walnut kernels was found to be a temperature-dependent reaction، with Q10 =1. 44- 2. 1. The results showed that CD and CT values could provide a proper estimation for oxidative stability of the nuts stored in ordinary condition، with an average error of approximately 12. 9%.

Fatty acid modified cellulose nanofibers (MCNFs) and TBHQ antioxidant were added to poly (lactic acid) (PLA) film. The combined effects of the MCNFs and TBHQ on the morphological، thermal، mechanical and barrier properties of PLA film were analyzed. The morphology of fracture surfaces evaluated by field emission scanning electron microscopy (FE-SEM). XRD results showed that the crystallinity of the PLA film with added MCNFs was substantially higher than that of pure PLA and antioxidant active PLA films. Glass transition and melting temperatures changed with the addition of these two components. The addition of 3wt% of TBHQ to PLA films leads to a significant reduction.

The objective of this study was to evaluate the effect of process conditions and different pretreatments including ultrasound، microwave and osmotic dehydration on mass transfer and oil uptake during deep fat frying of potato slices. Ultrasound pretreatment was performed at frequency of 40 KHz for 10 and 30 minutes، microwave pretreatment was conducted at 5 W/g power and osmotic dehydration pretreatment was done in NaCl solutions with concentrations of 1 and 3 percent. Potato slices were then fried at 150، 170 and 190°C for 90، 180، 270 and 360 seconds. The results showed that ultrasound pretreatment for 10 minutes increases oil uptake of samples as compared with control sample، but when samples were exposed to ultrasound for 30 minutes، oil uptake was decreased. In addition، microwave pretreatment reduced oil uptake of potato slices insignificantly. Furthermore، osmotic dehydration pretreatment reduced oil uptake. In order to model oil uptake، experimental data were fitted with 6 models. The aforementioned models had the highest R2 and a minimum value of RMSE.