نشریه پژوهش های علوم و صنایع غذایی ایران
سال پانزدهم شماره 3 (پیاپی 57، امرداد و شهرویور 1398)

β-d- glucan as a soluble dietary fiber, has many desirable physical and physiological characteristic. In this research the effect of β-d- glucan and aging conditions (Time and Temperature) on some physicochemical and textural properties of frozen soy yogurt was investigated. Three variables including concentration of oat β-d- glucan (0, 1 and 2%), aging time (2, 13 and 24 h) and aging temperature (2, 4 and 6°C) were studied. The results showed that the addition of β-d- glucan to frozen yogurt increased viscosity, overrun, hardness and fat destabilization but the melting resistance and L*value were decreased.  In terms of aging conditions, it was revealed that increasing aging time could improve the quality of product whereas higher temperature had an undesirable effect on the quality of frozen soy yogurt. Longer aging time caused an increase in viscosity, hardness, fat destabilization and melting resistance. By increasing aging temperature, fat destabilization, overrun and viscosity were decreased and melting rate was increased. It was concluded that addition of β-d- glucan as a dietary fiber and prolonged aging time at low temperature could adjust textural properties of frozen soy yogurt and improve quality of this frozen dessert.

Biodegradable films containing lactic acid bacteria (LAB) are considered as new tools for advanced methods of food storage. In this study, Lactobacillus casei ATCC 39392 (L. casei 39392) was directly incorporated into a film formation solution of sodium caseinate (NaCas) and methyl cellulose (MC). The bioactive films were prepared in a manner to contain 106CFU/cm2 L. casei 39392. The moisture content, solubility in water, water vapor permeability (WVP), color, opacity, tensile strength, percentage of elongation at break, and the elastic modulus of the films were studied. The survival rate of L. casei 39392 was examined during 30 days of storage (5 °C, RH 75%) and the films inhibitory effect on the growth of Pseudomonas aeruginosa PTCC 10832 was also studied at 5 °C for 12 days. The presence of L. casei 39392 increased the film’s opacity and its WVP compared to the control (p 0.05). The survival rate of L. casei 39392 was higher in NaCas films than in methylcellulose films (p < 0.05). A higher inhibitory effect on the growth of P. aeruginosa 10832 (85.3%) was observed in the MC bioactive film, and this inhibitory effect became noticeable from the fourth day of storage onwards (p 0.05).  Our results showed that the bioactive films containing L. casei 39392 could be used and recognized as biofilms containing natural preservatives.

In this study, microemulsification of orange peel oil (OPO) using Tween 60:propanol with the ratio of 1:1 was studied under different conditions of pH, ionic strength, and sugar concentration.. Results showed that critical temperature (the temperature in which one- phase microemulsion system was still stable) for the microemulsions with higher sucrose concentrations (in the range between 0 to 30%) was lower while by decreasing in sugar concentration, critical temperature shifted to higher temperatures, as it reached to 90°C for the samples without sugar. The prepared microemulsions were stable at 5 and 25°C for seven days, but samples with higher concentrations of sugar (25 and 30%) became turbid at 45°C, whereas all other samples exhibited a one-phase microemulsion system at this temperature. Microemulsions were not stable at -3°C (freezing temperatures). In sensory evaluation, it was observed that the microemulsified OPO was dissolved in water as soon as it was added into the medium, in contrast to free essential oil as it was spreading on the surface of the solution. Encapsulation of OPO caused lower release of aroma, resulting a milder odor and taste (lower intensity) in samples which were preferred by the panelists. The overall acceptability of all samples containing OPO microemulsion was significantly higher than samples with free essential oil.

A synbiotic yogurt was provided by adding aerobic (Lactobacillus acidophilus) and anaerobic (Bifidobacterium bifidum) probiotics and inulin to the yogurt. The effects of aerobic and anaerobic probiotics, storage time, and inulin on the physicochemical/microbial properties of synbiotic yogurt in terms of acidity, viscosity, syneresis, and microbial count were studied. A head-space solid phase microextraction-gas chromatography (HS-SPME-GC) method was used to extract and detect of VOCs profile (total peak area and total peak height) of yogurt sample by nano-sized polyaniline fiber. The D-Optimal Combined Design (DOCD) was used to analyze the effect of probiotics type (aerobic and anaerobic), inulin percent (W/W %), and storage time of yogurt (day) on the physicochemical/microbial properties of synbiotic yogurt. Results showed that the aerobic and anaerobic probiotics, inulin, and storage time of yogurt affect the yogurt physicochemical/microbial property and there were relations between the physicochemical/microbial properties of yogurt and VOCs gas chromatography profile (total peak area and total peak height). The current research also enables us to obtain microbial count by total peak area and total peak height of the VOCs GC-profile of yogurt sample.

Water in oil emulsions could be used for preparing low fat food products or encapsulating water soluble sensitive constituents. In this research, vitamin C loaded water in oil microemulsions prepared using spontaneous method without any co-surfactant. In spontaneous method, microemulsions are formed based on surfactant affinity toward continues phase and are thermodynamically stable. Results showed that by increasing vitamin C concentration, droplets size of emulsions increased from 66.7 nm for pure water to 214.3 nm for 3% loaded microemulsions and poly dispersity index increased from 0.15 to 0.501. Visual appearance of microemulsions changed from transparent for pure water containing microemulsions to opaque for 3% vitamin C loaded emulsions. By increasing vitamin C concentration, viscosity decreased from 115.4 to 87.9 mPa.s. This research showed that up to 3% vitamin C containing microemulsions could be prepared without co-surfactants.

In the present study, the effects of addition of quince pomace powder (0- 15%) and water content (25- 35%) on the batter rheological properties, physicochemical characterizes and sensory properties of sponge cake were evaluated. The results showed that increasing substitution of quince pomace increased the viscosity and consistency batter and the dietary fiber, firmness, overall acceptability of cake and reduced the moisture content, and density of cake. Results of RSM based desirability function showed cakes formulated with 12.56% of quince pomace powder and 29.62% of water content had the most and desired physicochemical quality. Total phenol content (7.71 mg/g), iron (0.263 mg/Kg dry weight) and calcium (340 mg/Kg dry weight) of the control sponge cake was improved to 8.32 (mg/g), 0.361 (mg/Kg dry weight) and 1160 (mg/Kg dry weight) in the optimal sponge cake, respectively. SEM results showed the quince powder increased in the number of cavities in the cake's structure and the uniformity of these cavities.