Food Engineering / Gıda Mühendisliği
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Article Citation - WoS: 5Citation - Scopus: 6The Effect of Sporulation Medium on Alicyclobacillus Acidoterrestris Guaiacol Production in Apple Juice(Academic Press Inc., 2016) Molva, Çelenk; Baysal, Ayşe HandanThe present study evaluated the effect of sporulation medium on guaiacol formation from vanillin and vanillic acid by Alicyclobacillus acidoterrestris DSM 3922 in the reconstituted apple juice (pH 3.82, °Brix 11.3). For sporulation, potato dextrose agar and Bacillus acidoterrestris agar were used. After heat-activation, spores were turned into vegetative cells and inoculated into juice samples to a final concentration of 103 or 105 CFU/mL. Samples were incubated at 37 °C for 264 h and guaiacol concentration was determined using peroxidase enzyme colourimetric assay. Based on the results, the conversion of vanillic acid into guaiacol was faster than that of vanillin among both cell suspensions. Also, there were no significant differences among any of the samples inoculated into apple juice spiked with vanillin at the end of the incubation period (P > 0.05). In the case of vanillic acid, the guaiacol concentrations were significantly different among cells activated from spores produced on PDA and BATA (P < 0.05). The obtained results suggested that type of sporulation medium composition may affect the guaiacol concentration depending on inoculum level and type of precursor present in the apple juice.Article Citation - WoS: 9Citation - Scopus: 12Effects of Pomegranate and Pomegranate-Apple Blend Juices on the Growth Characteristics of Alicyclobacillus Acidoterrestris Dsm 3922 Type Strain Vegetative Cells and Spores(Elsevier Ltd., 2015) Molva, Çelenk; Baysal, Ayşe HandanThe present study examined the growth characteristics of Alicyclobacillus acidoterrestris DSM 3922 vegetative cells and spores after inoculation into apple, pomegranate and pomegranate-apple blend juices (10, 20, 40 and 80%, v/v). Also, the effect of sporulation medium was tested using mineral [Bacillus acidoterrestris agar (BATA) and Bacillus acidocaldarius agar (BAA)] and non-mineral containing media [potato dextrose agar (PDA) and malt extract agar (MEA)]. The juice samples were inoculated separately with approximately 105CFU/mL cells or spores from different sporulation media and then incubated at 37°C for 336h. The number of cells decreased significantly with increasing pomegranate juice concentration in the blend juices and storage time (p<0.001). Based on the results, 3.17, 3.53, and 3.72 log cell reductions were observed in 40%, 80% blend and pomegranate juices, respectively while the cell counts attained approximately 7.17logCFU/mL in apple juice after 336h. On the other hand, the cell growth was inhibited for a certain time, and then the numbers started to increase after 72 and 144h in 10% and 20% blend juices, respectively. After 336h, total population among spores produced on PDA, BATA, BAA and MEA indicated 1.49, 1.65, 1.67, and 1.28 log reductions in pomegranate juice; and 1.51, 1.38, 1.40 and 1.16 log reductions in 80% blend juice, respectively. The inhibitory effects of 10%, 20% and 40% blend juices varied depending on the sporulation media used. The results obtained in this study suggested that pomegranate and pomegranate-apple blend juices could inhibit the growth of A. acidoterrestris DSM 3922 vegetative cells and spores.Article Citation - WoS: 38Citation - Scopus: 49Antimicrobial Activity of Grape Seed Extract on Alicyclobacillus Acidoterrestris Dsm 3922 Vegetative Cells and Spores in Apple Juice(Academic Press Inc., 2015) Molva, Çelenk; Baysal, Ayşe HandanThe present study evaluated the antimicrobial activity of grape seed extract (GSE) against Alicyclobacillus acidoterrestris vegetative cells and spores in apple juice (pH 3.82, °Brix 11.3) during storage at 37°C. After 336h, reductions in the cell numbers were 3.14, 3.55, 3.8, 4.1, and 4.63 logCFU/mL in the apple juice with 0.23, 0.45, 0.9, 1.8, and 3.6% of GSE, respectively. The Weibull was found to be the best fitted model for cell inactivation kinetics (R2>0.988). Moreover, the spores produced on different sporulation media (potato dextrose agar, malt extract agar, Bacillus acidoterrestris agar, and Bacillus acidocaldarius agar) were treated with GSE (0-1.9%, v/v). While control spores in apple juice without GSE increased by 2.2-2.6logCFU/mL within the first 48h, 0.9% and 1.8% of GSE inhibited the growth from all spore suspensions. Finally, scanning electron microscopy (SEM) indicated that the main target of the GSE may be the membrane of A. acidoterrestris cells leading to leakage of cellular constituents and may prevent the development of spores into vegetative cells. This study highlights the potential use of the by-products of the fruit juice/beverage industry as natural antimicrobials to inhibit the growth of A. acidoterrestris. © 2014 Elsevier Ltd.Article Citation - WoS: 29Citation - Scopus: 31Evaluation of Bioactivity of Pomegranate Fruit Extract Against Alicyclobacillus Acidoterrestris Dsm 3922 Vegetative Cells and Spores in Apple Juice(Academic Press Inc., 2015) Molva, Çelenk; Baysal, Ayşe HandanThis research evaluated the antimicrobial activity of commercial pomegranate extract (POMELLA®, PE) against Alicyclobacillus acidoterrestris vegetative cells and spores (approximately 105 log CFU/mL) in apple juice (pH 3.82, °Brix 11.3) during storage at 37°C. After 240h, the cell counts were reduced from the initial log count (CFU/mL) by 2.84, 3.26, 3.32, 3.46 and 3.56 in the apple juice with PE at the concentrations of 2.5, 5, 10, 20 and 40μg/mL, respectively. On the other hand, counts of the control reached 7.36 log CFU/mL after 24h. The Weibull model satisfactorily described the survival curves of cell inactivation kinetics (R2 > 0.983). While the growth of all spores obtained from different sporulation media (potato dextrose agar, malt extract agar, Bacillus acidoterrestris agar, and Bacillus acidocaldarius agar) was inhibited in the apple juice with PE (2.5-40μg/mL), the control spores increased by 1.9-2.2 log CFU/mL after 336h. Based on the scanning electron microscopy (SEM) imaging, vegetative cells indicated substantial damage and spore germination was inhibited in the apple juice with PE. The results showed that PE can have possible uses as a natural antimicrobial to control the growth of A.acidoterrestris vegetative cells and spore germination in the apple juice. © 2015 Elsevier Ltd.Article Citation - WoS: 14Citation - Scopus: 16Effect of Sporulation Medium on Wet-Heat Resistance and Structure of Alicyclobacillus Acidoterrestris Dsm 3922-Type Strain Spores and Modeling of the Inactivation Kinetics in Apple Juice(Elsevier Ltd., 2014) Molva, Çelenk; Baysal, Ayşe HandanAlicyclobacillus acidoterrestris is a spoilage bacterium in fruit juices leading to high economic losses. The present study evaluated the effect of sporulation medium on the thermal inactivation kinetics of A. acidoterrestris DSM 3922 spores in apple juice (pH3.82±0.01; 11.3±0.1 °Brix). Bacillus acidocaldarius agar (BAA), Bacillus acidoterrestris agar (BATA), malt extract agar (MEA), potato dextrose agar (PDA) and B. acidoterrestris broth (BATB) were used for sporulation. Inactivation kinetic parameters at 85, 87.5 and 90°C were obtained using the log-linear model. The decimal reduction times at 85°C (D85°C) were 41.7, 57.6, 76.8, 76.8 and 67.2min; D87.5°C-values were 22.4, 26.7, 32.9, 31.5, and 32.9min; and D90°C-values were 11.6, 9.9, 14.7, 11.9 and 14.1min for spores produced on PDA, MEA, BATA, BAA and BATB, respectively. The estimated z-values were 9.05, 6.60, 6.96, 6.15, and 7.46, respectively. The present study suggests that the sporulation medium affects the wet-heat resistance of A. acidoterrestris DSM 3922 spores. Also, the dipicolinic acid content (DPA) was found highest in heat resistant spores formed on mineral containing media. After wet-heat treatment, loss of internal volume due to the release of DPA from spore core was observed by scanning electron microscopy. Since, there is no standardized media for the sporulation of A. acidoterrestris, the results obtained from this study might be useful to determine and compare the thermal resistance characteristics of A. acidoterrestris spores in fruit juices. © 2014 Elsevier B.V.Article Citation - WoS: 76Citation - Scopus: 89Uv-C Light Inactivation and Modeling Kinetics of Alicyclobacillus Acidoterrestris Spores in White Grape and Apple Juices(Elsevier Ltd., 2013) Baysal, Ayşe Handan; Molva, Çelenk; Ünlütürk, SevcanIn the present study, the effect of short wave ultraviolet light (UV-C) on the inactivation of Alicyclobacillus acidoterrestris DSM 3922 spores in commercial pasteurized white grape and apple juices was investigated. The inactivation of A. acidoterrestris spores in juices was examined by evaluating the effects of UV light intensity (1.31, 0.71 and 0.38mW/cm2) and exposure time (0, 3, 5, 7, 10, 12 and 15min) at constant depth (0.15cm). The best reduction (5.5-log) was achieved in grape juice when the UV intensity was 1.31mW/cm2. The maximum inactivation was approximately 2-log CFU/mL in apple juice under the same conditions. The results showed that first-order kinetics were not suitable for the estimation of spore inactivation in grape juice treated with UV-light. Since tailing was observed in the survival curves, the log-linear plus tail and Weibull models were compared. The results showed that the log-linear plus tail model was satisfactorily fitted to estimate the reductions. As a non-thermal technology, UV-C treatment could be an alternative to thermal treatment for grape juices or combined with other preservation methods for the pasteurization of apple juice.Article Citation - WoS: 46Citation - Scopus: 53Extracellular Enzyme Production and Enterotoxigenic Gene Profiles of Bacillus Cereus and Bacillus Thuringiensis Strains Isolated From Cheese in Turkey(Elsevier Ltd., 2009) Molva, Çelenk; Sudağıdan, Mert; Okuklu, BurcuThe aim of the present study was to investigate the biochemical characteristics, extracellular enzyme production and enterotoxigenic genes contents of 6 Bacillus cereus and 22 Bacillus thuringiensis strains, isolated from 100 cheese samples in Turkey. Crystal morphologies of B. thuringiensis strains were found either spherical (n = 12) or spherical and irregular-shaped (n = 10) by phase contrast microscopy. B. cereus and B. thuringiensis strains were found to produce extracellular enzymes, respectively: gelatinase (83% and 91%), DNase (83% and 77%), lecithinase (83% and 95%), protease on skim milk agar (100% and 100%), protease on milk agar (100% and 91%), protease on casein agar (83% and 77%), xylanase (100% and 45%), and cellulase (0% and 41%), and amylase (83% and 27%). All of the strains, except for Bt-D1, hydrolyzed Tween 20 (96%), but not Tween 80 or tributyrin. Pectinolytic activity was obtained to be the least frequent (4%). PCR analysis showed that all strains contained nheA, nheB, nheC and hblD genes. The hblA and hblC genes were present in 2 and 4 of B. thuringiensis strains, respectively. The bceT gene was detected in 1 B. cereus and 9 B. thuringiensis strains. The entFM gene was detected more frequently in B. thuringiensis (82%) than in B. cereus strains (50%). To our knowledge, this is the first report about the isolation and identification of enterotoxigenic B. cereus and B. thuringiensis strains from cheese samples in Turkey.