Investigation of physicochemical, microbial and sensory properties of low-fat jug cheeses containing β-glucan powder and ethanolic extract of menthe longifolia

Jug cheese is a kind of hard cheese which traditionally produce from raw milk of cow, sheep and sometimes goat in west part of Iran. Its rippening period passed through the clay jug inside the soil, so it contains some varieties of microorganisms that provide it with specific and unique sensory properties. However, the transmission of some pathogenic bacteria in this product and its high fat content is very important in terms of general health.Therefore, the general objective(aim) of this study was to investigate the physicochemical, antimicrobial and sensory properties of low-fat jug cheese( produced produced from milk with 1.5% fat) Jug cheese containing Beta-Glucan powder ( 0. 25%, 0.5%, 1%) and menthe longifolia ethanolic extract (0.1, 0.2 and 0.3) and with compare the results with control cheese (produced from milk with 3% fat)during 60 days of ripening. Antibacterial results showed that properties using beta-glucan had no significant effect on the antimicrobial properties of the treatments and The use of ethanolic extract of mentha longifolia and increasing its concentration had significantly in the most extreme of the antimicrobial properties of treatments. According to results after 60 days of storage, the treatments containing 0.3% of Mentha longifolia extract, in comparison to the other treatments and Showed the most extreme decrease in the total count of microorganisms, lactobacillus, mould and yeast, coliforms, esherchia coli and staphylococcus aureus. The physicochemical properties investigation showed that the protein, fat, acidity and nitrogen soluble in water durin the preservation period have increased and pH, tissue hardness of the samples have significantly (p≤0.05) decreased. The results of sensory evaluation of cheese showed that the treatment which contained 0.5% beta-glucan and 0.3% ethanolic extract of mentha longifolia has the highest sensory properties. So using 0.5% beta-glucan and 0.3% ethanolic extract of menthe longifolia in low- fat cheese formulas can produce safe cheese with microbial and optimum texture at standard level. Jug cheese was produced from 1.5 fat cow milk obtained from Spoota Food Industries Complex, Urmia, Iran. First, milk was heated at 32-35ºC and cooled at 30ºC, then 0.06% cheese rennet (plant rennet, Cominux, Spain) was added and mixed for 5 minutes. After coagulation (45 min), the cheese was cut into 1*1*1 slices and wrapped in a cloth to be kept in room temperature for 12 hours under 0.1 weight plates for dewatering. Coagulants were impregnated in 3.5% salt solutions (since jug chesses is granular, there was no need to chop the samples). Therefore, the samples were squeezed into jugs and the jug was buried top-down in a 1-meter depth hole. Physicochemical, microbial and sensory properties of samples immediately after they were produced and on day 60 (1440 hours) were measured (Pakbin, 1391). Total protein was determined by macro-kjeldahl method with national standard No. 639. Soluble nitrogen was determined by kjeldahl method. Fat was determined by Gerber's method with national standard No. 366 (Anonymous, 1370). Level of moisture was determined by national standard No. 1753. pH was determined by a MA-Mettler pH-meter and titratable acidity (percentage of lactic acid) was determined by 0.1 normal and phenolphthalein as identifiers using national standard No. 2852 (Anonymous, 1385). Ash from cheese samples was measured by burning and full oxidation of food products in an oven at 550ºC (Khosroshahi, 1387). The Mohr titration method with national standard No. 1809 was used to measure salt in cheese samples (Anonymous, 1356). Tissue hardness (pressure or density) was measured using Universal Instron model 1140 and a probe at a constant speed of 100 mm/min. Compression test of cheese samples was done using a 36mm diameter cylindrical probe (hoseini et al, 1392). To measure number of living microorganism in jug cheese samples. To do so, 1g cheese was chopped with a sterile crucible or a mortar and mixed with 9cc buffered Peptone water. About 0.1cc of the solution was cultivated on a special medium by surface cultivation method. Number of microorganisms was measured by national standard No. 5484 in Kant Agar Plate mediums at 30ºC for 72 hours (Anonymous, 1381). Lactobacillus was measured in an MRS-Bile Agar medium (0.15% bile salt) with national standard No. 17164 at 37ºC for 72 hours (Anonymous, 1392). Molds and yeasts were measured, based on national standard No. 10154, in the YGC Agar medium for 5 days at 25ºC (Anonymous, 1386). To measure total formations, based on national standard No. 11166, a VRBA medium with two-layered pure palet method at 35ºC for 18-24 hours (Anonymous, 1387). E. coli was measured, with national standard No. 5234, in an EC Broth medium at 35ºC for 23 hours (Anonymous, 1394). Staphylococcus aureus was measured, based on national standard No. 6806-1, in a Bird-Parker medium with yolk and potassium tellurite at 37ºC for 48 hours (Anonymous, 1384). Sensory analysis was performed by 9 trained evaluators using a Five Point Hedonic Method with scales of one (very good), two (good), three (average), four (bad), and five (very bad) for taste, odor, tissue, and overall acceptability (Anonymous, 1387). In order to design the treatments, a completely randomized design with factorial arrangement was used. Treatments were designed with a control sample.To data analyze use Duncan one-way analysis of variance. The results of antimicrobial evaluation showed treatments containing 0.3% ethanolic extract of mentha longifolia compared to other treatments showed the greatest reduction in total count of microorganisms, lactobacillus, mildew and yeast, coliforms, E. coli, Staphylococcus aureus. Thus, results of the study showed physicochemical characteristics the amount of protein, fat, acidity and nitrogen soluble in water increased and pH, moisture and texture hardness of samples significantly decreased (p≤0.05). The evaluation of sensory properties showed that treatment containing 0.5% β-glucan and 0.3% ethanolic extract of mentha longifolia had the highest sensory acceptability. Therefore, the use of 0.5% β-glucan with 0.3% ethanolic extract of mentha longifolia in the formulation of low-fat jug cheese, can be produced safe cheese with microbial and optimum texture at standard level.