فصلنامه پژوهش و نوآوری در علوم و صنایع غذایی
سال سوم شماره 3 (پاییز 1393)

The effects of incorporated Spirulina platensis (0-0.5 %) and Zedo gum (0-0.5 %) during storage time (1-21 days) on different manufactured yogurt types (plain/probiotic) through 20 treatments using Central Composite Design were investigated. Qualitative indices like pH, titrable acidity, probiotic viability evaluation by MRS agar medium including vancomycin, antioxidative capacity by 1, 1diphenyl 2 picryl hydrazyl radical inhibition assay, proteolysis pattern by o-Phthalaldehyde assay and overall sensory acceptance by linear scale method were evaluated. Statistical analysis and modeling revealed that incorporated Spirulina amount and storage time had significant effect on the pH and acidity (P<0.05). Regarding Lactobacillus paracasei viability, it was affected significantly by microalgae amount, storage time and interaction of gum-Spirulina amount. Also all studied variables had significant effect on proteolysis index (P<0.05) which might be related to Spirulina’s stimulant effect on the proliferation of yogurt starters and probiotic strain. Statistical analysis showed antioxidative properties of Spirulina platensis and Zedo gum in yogurt samples. The highest sensory score was obtained at 0.1 % Spirulina and 0.25 % Zedo gum which indicated a positive role of Zedo gum in the application of microalgae from sensory aspects.

Mannan is a glycoprotein which consists of mannose polymers attached to the protein backbone that due to its natural amphiphilic compounds, it can be used as an effective bioemulsifier. Therefore, in this study, optimization and screening tests were conducted on the production of mannan from kluyveromyces marxianus using combinatorial method of the fractional of full factorial design and response surface together with determining the influence of the variables of lactose concentration based on whey powder, the concentration of yeast extract, enzyme activator and pH. It was revealed that the four variables of lactose and yeast concentration, pH and temperature had the most influence on the production of the mannan. The optimization of effective factors using response surface methodology demonstrated suitable conditions for mannan production with the maximum of 209.23 mg/100 ml with concentration level of 52.60 gr/l of the lactose, 10.38 yeast extract, pH of 5.36 and the temperature of 31.90°C with the maximum growth rate of 0.401 h-1. Results also showed that monod’s model had high correlation coefficient (0.998) and therefore could be used for prediction of yeast growth behavior as well as mannan production.

In this study whey protein concentrate (WPC) at levels (0.1and 4%), soy protein isolate (SPI) at levels (0.1and 2%) and microbial transglutaminase (MTG) at levels (0.1and 2%) were used in low fat ice cream formulation (4% fat) and their effects were evaluated on the physicochemical and overall acceptance and their optimum amount was determined using response surface methodology. The amount of total solids in all samples was the same 34%). According to the results formulations containing WPC had higher viscosity and acidity but lower overrun, melting resistant and overall acceptance compared to the control sample (P<0.01). SPI resulted in greater viscosity and melting resistance but lower overrun and overall acceptance (P<0.01). MTG resulted in greater melting resistance, overrun and viscosity of the ice cream samples in comparison to control sample (P<0.01). But had no significant effects on overall acceptance and acidity (P>0.05). The result of optimization showed that the best levels of SPI, WPC and MTG were 0.06, 1.37 and 1.19 % respectively. Also in optimum levels, the amount of viscosity, melting resistance, overrun, acidity and overall acceptance were obtained 1700 cp, 52%, 49/54%, 28/5 dornik and 4.25, respectively.

In present study, whey protein hydrolysate was prepared using Alcalase 2.4L from whey protein concentrate. The effect of temperature (40, 45, 50 and 55°C), time (30, 60, 9, 120, 150, 180 and 210 m) and enzyme/substrate ratio (30, 60 and 90 Anson unit/kg protein), on degree of hydrolysis and antioxidant activity of product were investigated in a completely randomized design. The highest degree of hydrolysis was observed at 55°C, hydrolysis time of 180 minutes and enzyme/substrate ratio of 60 Anson unit/kg substrate. Under these conditions, degree of hydrolysis was 51.62%. The antioxidant activity of protein hydrolysate was studied using reducing power and Fe2+ chelating activity. At maximum degree of hydrolysis, Fe2+ chelating activity were obtained 50.41%. As well as under this condition reducing-power of protein hydrolysate was 0.156 which showed 20.47% reducing-power compared to 100 ppm ascorbic acid.

Nowadays, considering the increasing tendency for consuming low fat or non-fat products, it is preferred to use non-fat milk for yoghurt production. Cress seed has various pharmaceutical applications and for as much as it is known that this plant’s seeds have high mucilage compounds, in this study different concentration levels (0.05, 0.07, 0.1, 0.15% w/w) of the gum used. pH, acidity, water loss, viscosity and the texture (hardness, adhesiveness) of produced yogurt during the storage time (1, 7, 14 and 21 days) was evaluated. pH decreased in comparing to control samples by adding hydrocolloid level to low fat yogurt samples. A significant increase in acidity was observed during storage. With increasing gum level water loss of samples decreased. Hardness of the samples increased during storage. The result of this study shows that the cress seed gum has a good potential for being used as a stabilizer in yogurt formulation.

In this study carrot juice samples were sonicated according to a D-optimal design response surface with different treatment of sonication temperature (25, 37.5 and 500C), sonication time (10, 20 and 30 min) and sonication power (350, 400w) at a constant frequency of 24 kHz. The results showed that ultrasound temperature (P<0.01), time (P<0.01) and interaction between time and temperature (P<0.01) significantly decreased the peroxidase enzyme activity of carrot juice samples and a prediction model obtained with high coefficients determination (R2 98%). Enzyme activity thermal treated juice processed at 90-880C for 4 min was undetectable. Ultrasound time significantly decreased the L-value, a-value, b-value, and TCD Blank (P< 0.05) of carrot juice samples. Whereas ultrasound temperature significantly increased the a value (P<0.01) and TCD Blank (P<0.05) samples. The obtained results showed that, ultrasound treatment significantly decreased peroxidase enzyme activity due to cavitational effects and reduced color parameters degradation specially a-value of carrot juice. Thus in order to maintain the quality of processed carrot juice; ultrasound processing could be accompanied by additional measures such as exclusion of oxygen, refrigerated storage and the use of natural enzyme inhibitors.

In this study, an adaptive neuro-fuzzy inference system (ANFIS) used for the prediction of permeate flux as a function of the physico-chemical and operating parameters during ultrafiltration of milk. An ultrafiltration pilot plant equipped with hollow fiber module and polyethersulfone membrane (MWCO 10 kDa) was used to do the milk ultrafiltration with various physico-chemical properties, consists of five levels of pH (5.6, 6, 6.6, 6.9 and 7.6) and three levels of ionic strength (0.03, 0.06 and 0.12) and under different operating conditions including transmembrane pressure (TMP) at three levels (0.1, 0.3 and 1 atm), temperature at three levels (30, 40 and 50 ° C) and the flow rate at three levels (10, 30 and 46 m/s). In order to model the effects of operating parameters and physicochemical properties of milk on permeate flux, the experimental data was randomized. 30 % of the data for learning, 30% of the data for evaluation and 40 % of the data was used to test the model. The results showed that the Nero–Fuzzy modeling approach is capable to predict the permeate flux under various operating conditions and physiochemical characteristics of milk, and modeling results represented there was an excellent correlation (average R = 0.93) between the predicted data and experimental data.