مجله میکروب شناسی مواد غذایی
سال ششم شماره 3 (پاییز 1398)

This study was performed to produce a probiotic carrot juice-ice cream beverage. Designed in a random factorial CRD manner. For this purpose, both Lactobacillus casei and Bifidobacterium lactis (at 108 and 109 cfu/ml levels) were added to beverage formulation. The samples were stored at -5ºC for 21 days. Survival of bacteria, pH, titrable acidity (%), beta-carotene (%), total solids contents (%), phenolic components (µg/ml) and DPPH (%) were measured at 1, 6, 11, 16 days of storage. The number of viable cells were significantly decreased during the storage time. However, the number of L. casei and Bf. lactis were in the recommended range (106 cfu/ml) until last day of storage. The highest number of viable cells was for Bf. lactis. By increment the probiotics levels, the pH and total solids values were decreased. Treatments and storage time did not show any significant effect on the acidity of probiotic carrot juice-ice cream. The highest amounts of phenolic components were for 109 cfu/ml L. casei and 108 Bf. Lactis. During storage period, the phenolic compounds and antioxidant activity of all samples were significantly decreased. Increment the concentration of L. casei in beverage formulation leads to decreased DPPH percentage inhibitory, while, by increasing the Bf. lactis in samples, the antiradical activity was increased. Samples containing 109 cfu/ml L. casei and Bf. Lactis had the highest amounts of beta-carotene. According to obtained results, treatment E which contained 109 cfu/ml bifidobacteriun lactis was the best among other treatments.

Green and blue mold rot diseases caused by Penicillium digitatum and Penicillium italicum are the most important postharvest diseases of citrus fruit. In this research, the use of some essential oils (Cuminumcyminum, Zataria multiflora, Mentha piperita) to control blue and green molds in orange fruits was investigated. Valencia and Jiroft Local oranges were dipped in Penicillium italicum and P. digitatum suspension and were put in waxy papers sprayed with the essential oils at three levels (1, 2.5 and 5%), and thiabendazole fungicide (TBZ) 0.2%. Control fruits were put in waxy papers without any treatments. Then, all the fruits were stored at 8 oC and 85-90% relative humidity for 3 months. Essential oils of Cuminumcyminum (cumin)and Zataria multiflora (Shiraz origanum) were effective on control of blue and green molds in orange varieties at the levels of 5% and 1, 2.5 and 5%, respectively. These treatments had no significant differences with thiabendazole fungicide. The treatments containing mint essential oil had the highest level of rot by blue and green molds. The results of the sensory evaluation showed that the essential oils did not make any special taste in orange varieties. Essential oil of Shiraz origanum in different levels caused improper appearance in the skin of orange varieties and as a result, they obtained the fewer score in the sensory attributes (texture, acceptability). Therefore, for increasing the storage-life of Valencia and Jiroft Local oranges, application of waxy paper containing 5% of cumin essential oil was recommended.

Isolation and identification of lactic acid bacteria from local products can play an important role in the introduction of unique types of probiotics. The present study was conducted in an attempt to isolate lactic acid bacteria from local dairy produced in the township of Gorgan which had the ability to inhibit the growth of some gastrointestinal pathogens. In order to isolate lactic acid bacteria, cheeses samples were sub-cultured on media cultures of MRS agar, M17 Agar , KAA and MRS+Vancomycin. Then, isolates were identified based on general morphological characteristics, biochemical and sugar fermentation tests. Using agar well diffusion, the antibacterial activity of culture supernatant of lactic acid bacteria was tested against four pathogenic bacteria. Among 24 samples of local cheeses and dooghs and 4 industrial samples, a total of 73 isolates were identified in which Lactobacillus casei was the most frequent isolate with with 34.24%. Lactobacillus casei and Lactobacillus acidophilus isolated from sheep's dough and sheep's cheese and Lactobacillus delbrucki and Lactobacillus ramenosus isolated from sheep's dough showed significant antibacterial activity against all pathogenic bacteria studied, namely, E. coli, S. aureus, B. cereus and C. freundii. Moreover, lactic acid bacteria isolated from industrial samples showed less antibacterial activity compared to isolates of local samples. Overall according to antagonistic effects of lactic acid bacteria isolated from of Gorgan’s local dairy products, it is recommended to evaluate their use as probiotic bacteria.

Due to the synthetic and chemical nature of antibiotics and the phenomenon of body resistance against them, using herbal compounds to cure infections and diseases are being noticed a lot, today. In this study, extracting the herbs was done by soaking in 80% ethanol. Berberis Vulgaris (Barberry root)by HPTLC and Foeniculum vulgare (F. vulgare). Mill (Fennel seed)by GC/MS methods were analyzed. Disk diffusion and micro dilution methods were used to detection of the antibacterial effect in triplicate. Minimal of inhibitory concentration (MIC) between the antibacterial effects of Berberis vulgaris (B. vulgaris) and F. vulgare Mill extracts individually and combined with nisin and sodium diacetate showed a significant difference against Yersinia enterocolitica. Among the studied factors, nisin had the most antibacterial effect and followed by the extract of B. vulgaris and F. vulgare Mill respectively. The antibacterial effect of sodium diacetate against Y. enterocolitica was the lowest. These results were almost consistent with those achieved by disk diffusion method. Our results indicated that MIC of sodium diacetate and nisin combined with the extracts of B. vulgaris and F. vulgare mill had a remarkable decrease compared to each one's effect individually (P<0.05). Results were similar about minimal bactericidal concentration (MBC), which showed simultaneous usage of sodium diacetate with these extracts can decrease the use of sodium diacetate a lonely and its complications. Moreover, combined consumption of extracts with nisin decreases the use of the extracts and the resultant organoleptic changes.

Isolation and evaluation of the characteristics of lactic acid bacteria (LAB) from traditional fermented products have always the possibility of exposure to isolates with unique capabilities.In the present study after molecular identification of dominant LAB isolated from Tarkhineh, antibacterial and antifungal effects of the isolate and its bacteriocin-like substances on some foodborne indicators were investigated in accordance with the reference methods. Sequencing results of polymerase chain reaction led to the identification of Lactococcus lactis as dominant isolate. LAB isolate had proper antibacterial effect but there was no significant difference (P<0.05) between growth inhibitory diameter of S. aureus and E. coli in present of the isolate. Furthermore, the inhibitory effect of the crude supernatant was higher than that of the neutralized and treated supernatants against studied indicator bacteria. The highest reduction in the population of S. aureus (87.91%) was also observed in the presence of crude supernatant obtained from Logarithmic growth phase. The LAB isolate had the higher antifungal effect on A. flavus rather than A. niger, but the growth rate of A. niger compared to A. flavus was remarkably (P<0.05) higher in each of the third to sixth days of incubation in the presence of bacteriocin-like substances. Based on the results of this study, Lactococcus lactis isolate and its bacteriocin-like substrates can be used as starter culture in fermented food processing, or as bio-preservative in food and pharmaceutical industries.

Monacus purpureus (M. purpureus)produce six types of pigments from yellow to dark red color pigments. Monascus fungus has been welcomed due to its various pigment production and healing properties. The aim of this study, evaluation of incubation time (11-21days), salt (7-12 %) and date waste (15-55%) in production of orange pigment by M. purpureus using response surface methodology in solid state. After optimization of these factors, it was showed the highest amount of orange pigment was obtained during the 21-day incubation period, 7% salt and the date syrup concentration was 55%. In optimum conditions, a maximum yield of orange pigment was 5.31 (ODU.ml-1), fermentation yield was 0.252 (ODU.ml-1.day-1), pigment production yield per biomass 0.623 (ODU.mg-1), yield of orange production per carbon source consumption 0.043 (ODU.gr- 1), the substrate conversion rate was 93 (%). The results of this study showed that date waste and Wheat Straw could be used as an affordable and effective substrate for the production of orange pigment by M. purpureus fungus.

Alicyclobacillus acidoterrestris (A. acidoterrestris) is a thermophilic spore-forming bacterium that changes taste and smell of juices. The aim of this study was to investigate the inhibitory effect of nisin and ascorbic acid on A. acidoterrestris. Nisin (150 and 200 ppm) and ascorbic acid (100 and 250 ppm) were used in orange juice contaminated with A. acidoterrestris. Microbial, physicochemical, and sensory properties of the samples were investigated during 90 days’ storage. Adding nisin and ascorbic acid significantly (P<0.05) decreased the number of A. acidoterrestris in orange juice. The sample containing 200 ppm nisin+250 ppm ascorbic acid and the sample containing 200 ppm nisin+100 ppm ascorbic acid had the lowest number of A. acidoterrestris, respectively. During storage, the number of bacteria in samples containing nisin and ascorbic acid decreased significantly (P<0.05) so that no bacterial growth was seen in the sample containing 200 ppm nisin and 250 ppm ascorbic acid on the 60th and 90th days and the sample containing 200 ppm nisin+100 ppm ascorbic acid on the 90th day. Acidity of the samples increased and brix decreased significantly (P<0.05) during storage. The sample containing 150 ppm nisin +100 ppm ascorbic acid and the sample containing 200 ppm nisin +100 ppm ascorbic acid had the highest score of overall acceptance. The sample containing 200 ppm nisin +100 ppm ascorbic acid was selected as the best sample with regard to microbial and sensory properties. Therefore, orange juice containing nisin and ascorbic acid has suitable sensory quality and can affect the inhibition of A. acidoterrestris.

Lactococcus garvieae (L. garvieae) is the causative agent of lactococcosis in fish. These diseases can be transmitted to humans by direct contact or consumption of infected fish meat. In this study, the susceptibility of L. garvieae to the ethanolic and aqueous extracts of Juglans regia (J. regia) was evaluated. Ethanolic and aqueous extract of the J. regia was prepared and successively diluted to obtain minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against L. garvieae bacteria by successive dilution method. Also, the inhibition of bacterial growth was measured, using disk diffusion method. The results showed that the ethanolic extract of J. regia had bactericidal effect in concentrations of 37.5 mg/ml and also the bacteriostatic effect in the concentration of 18.75 mg/ml. However, the aqueous extract of J. regia, at concentrations of 75 mg/ml showed a bacterial effect and in the concentration of 37.5 mg/ml, the bacteriostatic effect was shown against bacterial growth. Considering the proper effect of these extracts on L. garvieae, more extensive studies was needed in clinical conditions in aquaculture farms. After determining the effective concentration, non-toxicity and the mechanism of their effect, extracts can be used in the treatment and prevention of disease.