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Öğe A comparative study of black mulberry juice concentrates by thermal evaporation and osmotic distillation as influenced by storage(Elsevier Sci Ltd, 2016) Dincer, Cuneyt; Tontul, Ismail; Topuz, AyhanIn the present study, black mulberry juice was concentrated using thermal evaporation and osmotic distillation after clarification and pasteurization. The main quality parameters of the concentrates were comparatively investigated after reconstitution with different storage times and temperatures. The parameters investigated were: color, turbidity, pH, titratable acidity, anthocyanin content, percent polymeric color, antioxidant activity, 5-hydroxymethylfurfural (HMF) content and volatile profile. The anthocyanin content, volatile content and turbidity values of osmotically distillated samples were found to be higher than those of the thermal concentrates. Neither HMF nor furfural was detected in the samples soon after the processing; however, levels of process contaminants were found to increase gradually throughout the storage period in both concentrates. Thermal evaporation resulted in markedly higher HMF and furfural formation in comparison to the osmotic distillation process. The anthocyanin content and antioxidant activity of the concentrates decreased, whereas polymeric color ratio and turbidity values increased within longer storage time and higher storage temperature. Industrial relevance: Concentration is one of the key steps affects the chemical and physical properties of black mulberry juice since black mulberry phytochemicals, mainly anthocyanins, are labile to heat treatment and storage. Thermal evaporation has some drawbacks such as loss of fresh juice flavors, color degradation, reduction of nutritional value and formation of mutagenic compounds such as HMF and furfural. These drawbacks require alternative methods that involve minimal processing. Osmotic distillation can be recommended for black mulberry juice concentration in order to preserve its heat-sensitive components and to produce high-quality product. (C) 2016 Elsevier Ltd. All rights reserved.Öğe A comparative study on phenolic composition, antioxidant activity and essential oil content of wild and cultivated sage (Salvia fruticosa Miller) as influenced by storage(Elsevier, 2012) Dincer, Cuneyt; Topuz, Ayhan; Sahin-Nadeem, Hilal; Ozdemir, Kubra Sultan; Cam, Ihsan Burak; Tontul, Ismail; Gokturk, Ramazan SuleymanIn the present study, the main quality parameters such as moisture content, extract yields, total essential oils, phenolic content and composition, and antioxidant activity of wild and cultivated Salvia fruticosa were elaborately investigated in six-month storage period for two consecutive years. The cultivated samples had higher total phenolic content than those of the wild samples. On the contrary, wild samples had higher extract yields, total flavonoids and total essential oils. Seventeen different phenolic compounds, composed of seven phenolic acids and ten flavonoids, were identified and quantified in both cultivated and wild S. fruticosa. Rosmarinic, p-coumaric and caffeic acids were determined to be the principal phenolic acids. The major flavonoids however were myricetin, morin and luteolin. The phenolic components of vanillic acid, gallic acid, chlorogenic acid, p-coumaric acid, myricetin and morin increased, whereas caffeic acid, catechin, epicatechin, luteolin and apigenin decreased by cultivation. The phenolic components were found to be either lower or not changed in consecutive harvesting year. They also did not significantly change during the storage period. The antioxidant activity of the samples was found to be higher for the second harvesting year whereas there were no significant differences between wild and cultivated S. fruticosa during storage period. (C) 2012 Elsevier B.V. All rights reserved.Öğe Comparative study on volatile compounds in Turkish green tea powder: Impact of tea clone, shading level and shooting period(Elsevier, 2013) Tontul, Ismail; Torun, Mehmet; Dincer, Cuneyt; Sahin-Nadeem, Hilal; Topuz, Ayhan; Turna, Turgay; Ozdemir, FeramuzThe objective of this study was to determine volatile compounds in green tea powders produced from a clone of two different teas (Camellia sinensis (L.) O. Kuntze) grown under different shade levels and harvested in two consecutive shooting periods. Both hydrodistillation and solid phase microextraction (SPME) methods were comparatively performed to identify maximum number and amount of volatile compounds. SPME method enables the identification of the greatest number of volatile compounds which principally comprise limonene, alpha-terpineol and heptanal. A few specific volatile compounds were identified for differentiation of green tea samples depending on the treatments, such as, heptanal in 1st shooting period, ethyl benzene, xylene and benzenacetal for 2nd shooting period, and phytol and tridecane for shading treatments. The treatments were significantly clustered either as tea clones or shooting period by the volatile compounds i.e. linalool, alpha-terpineol, 3-methylbutanal, 2-methylbutanal and p-cresol, 2,6-di-tert-buthyl determined in hydrodistillation method and tridecane, heptanal, linalool, nonanal, hexanal, alpha-terpineol, 1-pentanol, pentanal, dimethylsulfide, 2,2,4-trimethylhexane, limonene and 1-hexanol in SPME method as shown by principal component analysis (PCA). (C) 2012 Elsevier Ltd. All rights reserved.Öğe Convective and refractance window drying of cornelian cherry pulp: Effect on physicochemical properties(Wiley, 2018) Tontul, Ismail; Eroglu, Emrah; Topuz, AyhanCornelian cherry is a wild fruit contains considerable amounts of bioactive compounds such as ascorbic acid, anthocyanins, and phenolics. It has many different health beneficial effects due to these bioactive compounds. In the present study, convective drying and refractance window drying was employed in cornelian cherry pulp drying under different drying conditions. Moisture content (8.03-8.27g/100g), water activity (0.350-0.354), color properties, total monomeric anthocyanin content (247.47-347.3 mg C3G/kgdm), ascorbic acid content (0.81-0.90g/kgdm), radical scavenging activity (0.87-1.47g TEAA/kgdm), and 5-hydroxymethylfurfural (18.80-24.10 mg/l) content of the powders were determined. According to the results, physicochemical properties of the samples produced by refractance window drying were better than those of convective drying. Higher drying temperatures and air velocities provided higher content of total monomeric anthocyanin content and radical scavenging activity in hot air drying. However, drying temperature was found to be ineffective on all tested parameters in refractance window dried samples. Overall, refractance window drying of cornelian cherry pulp at 90 degrees C is recommended to achieve good physicochemical properties. Practical applicationsRefractance window drying is an innovative drying system usually used in the drying of liquid and semi-liquid foods. The results have shown that refractance window drying provided better physicochemical properties than convective drying in very short drying time.Öğe Effect of rolling methods and storage on volatile constituents of Turkish black tea(Wiley, 2017) Ozdemir, Feramuz; Tontul, Ismail; Balci-Torun, Ferhan; Topuz, AyhanThe leaves of harvested tea [Camellia sinensis (L.) O. Kuntze] can be processed into different products such as black tea, green tea and oolong tea. Black tea is the mostly consumed worldwide among these products. Black tea production is achieved by a series of processing steps namely withering, rolling, fermentation, drying, sieving and packaging. Rolling is one of the most important steps in the production as it ensures uniform maceration of tea leaves and promotes oxidation reactions catalysed by phenol oxidase enzymes during the fermentation process. The rolling of tea leaves is generally performed by either Crushing-Tearing-Curling (CTC), rotorvane or Orthodox methods. However, in Turkey, rolling is also performed using a combination of rotorvane and orthodox which is called the CAYKUR method. The rolling method provides a unique taste and flavours. Thus, this study was conducted to compare volatile constituents of the black teas produced by the above rolling methods and to determine the volatiles during the 6-month storage period. Some specific compounds such as 2,6-nonadienal, 3-hexen-2-one and dodecanal for CAYKUR, 2,5-octanedione for Orthodox and methylpyrazine for CTC were identified to differentiate the rolling system. This study also showed that a few compounds can be used as markers of storage. The number and amounts of volatiles, especially compounds with a high molecular weight, increased by storage. In addition, the flavour quality of the teas was evaluated by the Wickremasinghe-Yamanishi ratio (WYR), Mahanta ratio (MR) and Owuor Flavour Index.Öğe Effect of vegetable proteins on physical characteristics of spray-dried tomato powders(Sage Publications Ltd, 2016) Tontul, Ismail; Topuz, Ayhan; Ozkan, Ceren; Karacan, MerveIn the present study, the effectiveness of different vegetable proteins (pea protein isolate, soy protein isolate and zein from maize) at two different ratios (1% and 5%) on product yield and physical properties of spray-dried pulpy tomato juice was investigated. Additionally, these proteins were compared with whey protein concentrate which has a superior effect on spray dried products at the same concentrations. Additionally, plain tomato juice was also spray dried for comparison with vegetable proteins. The product yield of the tomato powders dried with the vegetable proteins was lower than with the whey protein concentrate. Among vegetable proteins, the highest product yield was produced with 1% soy protein isolate. In all products, there was a slight colour difference between the reconstituted tomato powders and the raw tomato juice, which indicated that pulpy tomato juice can be spray dried with minor colour change. All powders had unique free-flowing properties estimated as Carr index and Hausner ratio due to their large particles.Öğe Effects of different drying methods on the physicochemical properties of pomegranate leather (pestil)(Elsevier, 2017) Tontul, Ismail; Topuz, AyhanThe present study examines the effects of various formulations (traditional and hydrocolloid) and drying techniques [hot air drying at 50, 60 or 70 degrees C, microwave-assisted hot air drying (90 or 180 W) at 50, 60 or 70 degrees C and refractance window drying 90, 95 and 98 degrees C), in order to develop new methods for pomegranate pestil production. Water activity, pH, color, textural properties, total phenolic content, total flavonoids, total proantocyanidins, total monomeric anthocyanin, ascorbic acid, HMF content, antioxidant activity, phenolic and anthocyanin profiles and volatile compounds of the pestils were determined. Hydrocolloid formulation resulted in superior physicochemical properties of the pestils compared to traditional formulation. While microwave-assisted drying (MWD) provided higher phenolic content, refractance window (RW) drying provided higher ascorbic acid and anthocyanin content, and lower content of 5-hydroxymethylfurfural. Volatile compounds in the pestils showed that MWD promoted non-enzymatic browning reactions. Overall, the hydrocolloid formulation and the RW drying technique are the most promising processing methods for high-quality pestil production with high content of bioactive compounds. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Functional properties of chickpea protein isolates dried by refractance window drying(Elsevier Science Bv, 2018) Tontul, Ismail; Kasimoglu, Zehra; Asik, Serenay; Atbakan, Tugce; Topuz, AyhanIn the present study, the effect of Refractance Window (RW) drying on the functional properties of chickpea protein isolates was investigated and compared to freeze drying at different pH levels. The functional properties investigated were protein solubility, water and oil holding capacity, emulsifying properties, foaming properties, flocculation and coalescence indices and textural properties. The solubility, oil holding capacity and foam stability of the freeze dried protein isolates were determined to be higher than the RW dried samples. On the other hand, the RW dried samples had better water holding capacity and emulsion stability compared to the freeze dried protein isolates. The emulsion activity index, flocculation and coalescence indices of the chickpea protein isolates prepared by different drying techniques showed different tendencies depending on the pH level. Freeze dried protein isolates exhibited higher gelation ability than RW dried samples according to the texture profile analysis. This study clearly showed that the drying technique used in the preparation of protein isolates can affect their functional properties. (C) 2017 Elsevier B.V. All rights reserved.Öğe Growth, water use, yield and quality parameters in oregano affected by reduced irrigation regimes(Wiley, 2021) Hancioglu, Nurten E.; Kurunc, Ahmet; Tontul, Ismail; Topuz, AyhanBACKGROUND: Determining plant tolerance to water stress is necessary in irrigation scheduling, decisions concerning supplementary irrigation, planning and operation and, more importantly, the rational use of water resources. In the present study, effects of the irrigation regime on oregano growth, water use, yield and quality parameters were investigated using reduced irrigation regime treatments. RESULTS: Increased water stresses caused a decrease in all growth and yield parameters. Plant water use efficiency was not significantly different among the control, low and medium stress treatments, although it was the lowest for the extreme water stress treatment. Total essential oil yield was the only quality parameter demonstrating significant differences among treatments. Yield response factors were determined as 1.13, 1.12, 1.06 and 1.10 for total fresh, total dry, dry leaf and total essential oil yields, respectively. CONCLUSION: Yield response factors indicate that oregano plant is slightly sensitive to water stress. Although the yield parameters were affected by water stress, Origanum onites, under cultivation in recent years, might have developed a resistance mechanism for quality parameters because it has grown in very dry conditions under a natural environment for many years. However, the negative relationships between crop evapotranspirationversusessential oil, total phenolic and flavonoid contents and extract yield indicates that the quality parameters of oregano under low plant water consumption may be increased. (c) 2020 Society of Chemical IndustryÖğe The impact of refractance window drying conditions on the physical and microbiological properties of kefir powder(Elsevier, 2021) Tontul, Ismail; Ergin, Firuze; Eroglu, Emrah; Kucukcetin, Ahmet; Topuz, AyhanThe growing globally interest in healthy nutrition has resulted in a significant progress in the development of specialised and novel dairy powders. Refractance window has received increasing attention as a novel food-processing technology that is used at laboratory and industrial scale for food dehydration. This study was conducted determine the effect of refractance window drying conditions on the physical and microbiological properties of kefir powder. Refractance window drying is an innovative drying system that effectively utilizes conduction and radiation as heat transfer mechanisms and provides rapid drying with high quality. No previous study was conducted to produce kefir powder using refractance window drying. In the present study, the physical and microbiological properties of kefir powders produced by refractance window drying and freeze drying were compared during storage at 4 degrees C for 90 days. High drying temperature and thin spreading caused more colour changes in the samples. Refractance window drying of kefir resulted in a powder that had good flowability and low cohesiveness. Moreover, refractance window drying provided much better wettability, hygroscopicity and solubility compared to freeze drying. The survival of Lactococci, Lactobacilli, acetic acid bacteria and yeast in the kefir powders produced by RW drying at 50 degrees C was higher other counterparts at the end of storage.Öğe Influence of emulsion composition and ultrasonication time on flaxseed oil powder properties(Elsevier Science Bv, 2014) Tontul, Ismail; Topuz, AyhanEmulsification step of flaxseed oil microencapsulation was optimized using the Box-Behnken design of the response surface methodology in wall material concentration, oil loading and ultrasonic emulsification time. The optimization was performed to optimize the microencapsulation efficiency (MEE) and product yield (PY). Bulk density, particle size and hygroscopicity of the microcapsules were additionally determined. MEE showed a positive correlation with wall material concentration and ultrasonication time; however, increasing oil loading had an adverse effect. PY was mainly affected by wall material concentration and increasing the wall material concentration resulted in lower product yield. Longer ultrasonication time decreased particle size of the flaxseed oil emulsion, but particle size of the microcapsules did not significantly change. The particle size of the microcapsules was increased by increasing wall material concentration. Optimum conditions for the microencapsulation of flaxseed oil were predicted as a wall material concentration of 20 g.100 g(-1), an oil loading of 20 g oil.100 g(-1), wall material and an ultrasonication time of 120 s and this conditions provided 92.4% MEE and 68.7% PY. For practical conditions, wall material concentration of 20 g.100 g(-1), oil loading of 35.1 g oil.100 g(-1) wall material and ultrasonication time of 120 s can be suggested in the flaxseed oil microencapsulation process. (C) 2014 Elsevier B.V. All rights reserved.Öğe Influence of microwave, the combined microwave/hot air and only hot air roasting on the formation of heat-induced contaminants of carob powders(Taylor & Francis Ltd, 2018) Gunel, Zehra; Tontul, Ismail; Dincer, Cuneyt; Topuz, Ayhan; Sahin-Nadeem, HilalThis study aims to investigate the effects of microwave, combined microwave/hot air treatment and hot air-only roasting on the formation of heat-induced contaminants of carob powders. Moisture content, water activity and pH values of the product decreased with the increasing roasting time and microwave power, while browning index (BI) and ultraviolet absorbance (UV-A) values were increased. While L and b values of carob powders decreased with increasing the roasting time and microwave power, a and E values were increased. Varying roasting conditions also significantly affected the content of Maillard reaction products (MRPs): 5-hydroxymethylfurfural (HMF) (0.69-28.32 mg/kg dry matter), furfural (Öğe Irrigation water salinity effects on oregano (Origanum onites L.) water use, yield and quality parameters(Elsevier Science Bv, 2019) Hancioglu, Nurten Esen; Kurunc, Ahmet; Tontul, Ismail; Topuz, AyhanIrrigation water salinity effects on oregano growth, water use, yield and quality parameters were investigated. For this aim, eight irrigation water salinity levels including 0.54 (control), 1.2, 1.8, 2.5, 3.5, 5.0, 7.0 and 10 dS/m were utilized. The plants in all of 7 and 10 dS/m and two out of five replications of 5 dS/m treatment could not survive until the end of the experiment. The mean soil salinity and seasonal averaged drainage water salinity values increased with increasing salinities of applied irrigation water. Compared to control 27, 33, 44 and 74% reductions in total dry yields, and 27, 38, 49, and 77% decreases in dry leaf yields were calculated for 1.8, 2.5, 3.5 and 5 dS/m treatments, respectively. In general, increased irrigation water salinity caused increases in total phenolic content, total flavonoid content, extract yield which shows the amount of water extractable matter from the plants and antioxidant activity whereas significant decreases in total oil content. Among the essential oil components, carvacrol, beta-cymene and gamma-terpinene contents decreased with increasing water salinities up to 2.5 dS/m and after this level sharply increased but linalool content showed a reversed pattern. A threshold value of 0.50 dS/m was calculated for total fresh yield of oregano but it was not possible to determine a threshold salinity value for total dry yield, dry leaf yield and total oil content. Based on these results, oregano is a very sensitive plant to salinity.Öğe Microencapsulation of probiotic Saccharomyces cerevisiae var. boulardii with different wall materials by spray drying(Elsevier Science Bv, 2015) Arslan, Sultan; Erbas, Mustafa; Tontul, Ismail; Topuz, AyhanSaccharomyces cerevisiae var. boulardii have probiotic properties which are beneficial for human health. It has been commonly used as a drug against gastrointestinal disorders. Saccharomyces boulardii has been used in some food formulations in recent years, due to its probiotic properties. However, it is not sufficiently stable for food processing and gastrointestinal systems. In this study, S. boulardii was microencapsulated with six different wall materials (gelatin, whey protein concentrate, modified starch, maltodextrin, pea protein isolate and gum Arabic) and spray dried using two different inlet temperatures (80 degrees C and 125 degrees C). The highest product yield was obtained with whey protein concentrate and gum Arabic. Survivability of the S. boulardii did not change with the wall materials, but it increased at the lower drying temperature. Survivability in a simulated gastric solution test at different pH levels and durations showed that gum Arabic is the best wall material followed by gelatin and pea protein. The microcapsules produced at the higher drying temperature (125 degrees C) showed, a higher resistance to the gastric solution than those of the lower drying temperature (80 degrees C). In addition, survivability was decreased by increasing exposure time to the simulated gastric solution. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Mixture Design Approach in Wall Material Selection and Evaluation of Ultrasonic Emulsification in Flaxseed Oil Microencapsulation(Taylor & Francis Inc, 2013) Tontul, Ismail; Topuz, AyhanFlaxseed oil, sensitive to oxidation, was systematically microencapsulated with six triple wall materials combinations [carbohydrate (maltodextrine and two different modified starches (N-Lok (R) and HiCap (R) 100)); protein (sodium caseinate, whey protein concentrate); and Arabic gum] for the highest microencapsulation efficiency and oxidation stability. Proportions of the triple wall materials were optimized in mixture design using the quadratic model. Effects of Ultra-Turrax and ultrasonic emulsifications on microencapsulation efficiencies were additionally characterized in the optimized wall material combinations. The microcapsules produced were investigated for particle size distribution, moisture content, water activity, bulk density, and oxidative stability. Results showed that the combination of modified starch (Hi-Cap (R) 100)/Arabic gum/whey protein concentrate (4/0/1, w/w/w) provided the highest efficiency in flaxseed oil microencapsulation. However, the only successful combination in preventing flaxseed oil oxidation was maltodextrine/Arabic gum/whey protein concentrate (4/0/1, w/w/w). The microcapsules produced by ultrasonic emulsification had higher microencapsulation efficiency than that of Ultra-Turrax emulsification.Öğe Nanoencapsulation of Fish Oil and Essential Fatty Acids(Academic Press Ltd-Elsevier Science Ltd, 2017) Tontul, Ismail; Eroglu, Emrah; Topuz, Ayhan[Abstract Not Availabe]Öğe Optimization of aqueous extraction and spray drying conditions for efficient processing of hibiscus blended rosehip tea powder(Wiley, 2018) Eroglu, Emrah; Tontul, Ismail; Topuz, AyhanThe present study aimed to optimize extraction and spray-drying conditions used to produce rosehip tea powder from a blend of rosehip fruit and hibiscus. The optimum conditions of the extraction and spray drying processes were investigated using response surface methodology. The responses of the optimization were the ascorbic acid (AA) and total monomeric anthocyanin (TMA) content of the products. Optimal parameters for the extraction process were determined to be 5.3% loading ratio for 5.4 min at 64 degrees C. For the spray-drying process, an inlet air temperature of 130 degrees C, outlet air temperature of 85 degrees C, and 18.4% maltodextrin ratio was found to be optimal. The powders produced at these conditions were stored at 4 degrees C and ambient temperature for 90 days to test the stability of AA and TMA. The degradation rates at 4 degrees C and at ambient temperature were found to be 41.4 and 48.2% for AA and 23.3 and 37% for TMA, respectively. Practical applicationsNowadays there is a significant increase in the use of foods that are easy to prepare for consumption or ready for direct consumption. When consumers choose these products, they consider both ease of use and product quality. Tea bag and similar products are one of the most widespread product groups in this area. However, there are some disadvantages such as the waste problem and inadequate brewing conditions in use of these products. The solution of these problems requires alternative methods to prepare the product. The transformation of rosehip tea into instant rosehip tea form at optimum conditions determined in the current study can be used as an alternative method to solve these problems.Öğe The oxidative stability of flavoured virgin olive oil: the effect of the water activity of rosemary(Springer, 2018) Kasimoglu, Zehra; Tontul, Ismail; Soylu, Aleyna; Gulen, Kubra; Topuz, AyhanFlavoured olive oil gained has importance in terms of its sensorial properties and oxidative stability in recent years. However, the water activity level of the flavouring agent can be important for oxidative stability. Therefore, the aim of this study was to determine the effect of the water activity of rosemary, which was used as a flavouring agent, on the oxidative stability of olive oil. For this purpose, rosemary samples were adjusted to different levels of water activity (0.17, 0.24 and 0.44) and used for the aromatization of virgin olive oils. At the end of the aromatization, the olive oil samples were exposed to an accelerated oxidation test at 60 A degrees C for 28 days. The peroxide, p-anisidine, TOTOX (total oxidation index), free fatty acid, chlorophyll, carotenoid and specific extinction values of the samples were determined. According to the results, the oxidation of olive oils is limited by decreased water activity values in the rosemary samples. Moreover, unflavoured oils were identified as being more sensitive to oxidation when compared to flavoured oils. Additionally, storage time had important effect on all of the analysed parameters. The present research showed that the water activity of rosemary, when used as condiment, affected the oxidative stability and carotenoid content of virgin olive oil. Using rosemary with a low water activity value to flavour olive oil was more effective in terms of oxidative stability. These findings implied that the oxidation of flavoured olive oil could be decreased by decreasing the water content of the condiment used.Öğe Phenolic composition and antioxidant activity of Salvia tomentosa Miller: Effects of cultivation, harvesting year, and storage(2013) Dinçer, Cüneyt; Tontul, İsmail; Çam, İhsan Burak; Özdemir, Kübra Sultan; Topuz, Ayhan; Şahin, Hilal NadeemSalvia tomentosa is a common medicinal plant, and it is consumed as an herbal tea in some Mediterranean countries. It has been extensively collected from its natural habitat, and careless collection has caused the recent extinction of some plants. The present study was undertaken to cultivate S. tomentosa and compare the phenolic composition and antioxidant properties of wild and cultivated plants. Total phenolics, total flavonoids, and antioxidant activity of S. tomentosa ranged between 49.27 and 66.15 mg GAE g1 dry weight (dw), 36.27 and 40.83 mg catechin g1 dw, and 1.77 and 2.29 mg dw mg1 DPPH, respectively. Total phenolic content of the cultivated samples was higher than that of wild samples. Seventeen different phenolic compounds, comprising 7 phenolic acids and 10 flavonoids, were identified and quantified in S. tomentosa. As with the many Salvia species, rosmarinic acid was quantified as the main component of S. tomentosa. It was followed by caffeic acid, morin, p-coumaric acid, and myricetin. Chlorogenic acid, p-coumaric acid, morin, kaempferol, hesperetin, and apigenin were increased through cultivation; gallic acid, caffeic acid, ferulic acid, rutin, catechin, and epicatechin were decreased. During the 6-month storage only caffeic acid changed significantly.Öğe Physical and microbiological properties of yoghurt powder produced by refractance window drying(Elsevier Sci Ltd, 2018) Tontul, Ismail; Ergin, Firuze; Eroglu, Emrah; Kucukcetin, Ahmet; Topuz, AyhanThe present study aimed to determine the effect of refractance window (RW) drying comparatively with freeze drying on some physical properties and microbiological properties of yoghurt powder. Physical properties of yoghurt powders obtained by RW drying were generally better than those of yoghurt powders obtained by freeze drying except for colour properties. RW drying caused reduction in the counts of yoghurt bacteria during drying, and this reduction increased as the drying temperature increased. Spreading thickness did not play a critical role on the viability of yoghurt bacteria in dried samples. The viability of yoghurt bacteria in yoghurt powders was observed during 90 days of storage at 4 degrees C. At the end of storage period, the survival of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in the yoghurt powders produced by RW drying at 50 degrees C was higher than those produced by RW drying at 60 degrees C and 70 degrees C. (C) 2018 Elsevier Ltd. All rights reserved.
