Effect of freezing rate and storage time on quality parameters of strawberry frozen in modified and home type freezer

Freezing rate and storage time are the most important parameters in the losses of bioactive compounds of food during the freezing process. For this reason, the quality of strawberries which were frozen at different freezing mediums and the effect of storage time on samples were investigated in this research. The freezer section of the domestic refrigerator was used for slow freezing. Besides that, a modified freezer cabinet which capable of blowing air at a speed of 1.2 m/s at -30°C designed and produced by Bosch und Siemens Hausgerate GmbH (Çerkezköy,Turkey) was used for quick freezing. In the quick freezing chamber inside the refrigerator, the samples were provided to be frozen with a higher freezing speed than the static freezing unit of the refrigerator. Freezing time and freezing rates were determined from the cooling curves obtained experimentally. Slow and quick frozen samples were stored at −25°C for 4 months. Drip loss, total phenolic content, ascorbic acid content and total monomeric anthocyanin content of samples were significantly different after freezing and during storage time. It has been determined that higher freezing rate is essential for the better preservation of bioactive compounds of the strawberries. Freezing should be done at an appropriate freezing rate to preserve the cell structure and the nutritional content of strawberries

Production of Antimicrobial Films by Incorporation of Partially Purified Lysozyme into Biodegradable Films of Crude Exopolysaccharides Obtained from Aureobasidium pullulans Fermentation

Antimicrobial films were produced by incorporating partially purified lysozyme into films of crude exopolysaccharides (59 % pullulan) obtained from Aureobasidium pullulans fermentation. After film making, the films containing lysozyme at 100, 260, 520 and 780 μg/cm2 showed 23 to 70 % of their expected enzyme activities. The highest recovery of enzyme activity (65–70 %) after the film making was obtained in films prepared by incorporating lysozyme at 260 μg/cm2 (1409 U/cm2). The incorporation of disodium EDTA×2H2O and sucrose did not affect the initial lysozyme activity of the films significantly. With or without the presence of disodium EDTA×2H2O at 52 or 520 μg/cm2, lysozyme activity showed sufficient stability in the films during 21 days of cold storage. However, the presence of sucrose at 10 mg/cm2 in the films caused the destabilization of part of enzyme activity (almost 35 %) at the end of storage. The combinational incorporation of lysozyme at 780 μg/cm2 (4227 U/cm2) and disodium EDTA×2H2O at 520 μg/cm2 gave antimicrobial films effective on Escherichia coli. However, in the studied lysozyme concentration range the films did not show any antimicrobial activity against Lactobacillus plantarum. This study clearly showed that the partially purified lysozyme and crude exopolysaccharides from Aureobasidium pullulans may be used to obtain antimicrobial films to increase the safety of foods

Evaluation and production of ready-to-eat meals

3rd Seminar on Risk Management by Hygienic Design and Efficient Sanitation Programs; Tallinn; Estonia; 4 May 2009 through 6 May 2009Ready-to-eat (RTE) is defined as the status of the food being ready for immediate consumption at the point of sale or serve. It could be served as raw or cooked, hot or chilled, and can be consumed without further heat-treatment including reheating (Anon., 2001). RTE vegetables and salads, also called minimally-processed products, are raw products that must preserve as much as possible the nutritional, sensorial and microbial qualities of fresh products. A very wide range of vegetables are used, both cut and whole. Even during refrigerated storage, the fresh fruits and vegetables are characterized by active metabolism

Production of Antimicrobial Films by Incorporation of Partially Purified Lysozyme into Biodegradable Films of Crude Exopolysaccharides Obtained from Aureobasidium pullulans Fermentation

Antimicrobial films were produced by incorporating partially purified lysozyme into films of crude exopolysaccharides (59 % pullulan) obtained from Aureobasidium pullulans fermentation. After film making, the films containing lysozyme at 100, 260, 520 and 780 μg/cm2 showed 23 to 70 % of their expected enzyme activities. The highest recovery of enzyme activity (65–70 %) after the film making was obtained in films prepared by incorporating lysozyme at 260 μg/cm2 (1409 U/cm2). The incorporation of disodium EDTA×2H2O and sucrose did not affect the initial lysozyme activity of the films significantly. With or without the presence of disodium EDTA×2H2O at 52 or 520 μg/cm2, lysozyme activity showed sufficient stability in the films during 21 days of cold storage. However, the presence of sucrose at 10 mg/cm2 in the films caused the destabilization of part of enzyme activity (almost 35 %) at the end of storage. The combinational incorporation of lysozyme at 780 μg/cm2 (4227 U/cm2) and disodium EDTA×2H2O at 520 μg/cm2 gave antimicrobial films effective on Escherichia coli. However, in the studied lysozyme concentration range the films did not show any antimicrobial activity against Lactobacillus plantarum. This study clearly showed that the partially purified lysozyme and crude exopolysaccharides from Aureobasidium pullulans may be used to obtain antimicrobial films to increase the safety of foods

Akgemre ve çekirdeksiz taze üzümün şuruplu ve şurupsuz dondurulması ve depolanması aşamasında enzimlerin üzüm kalitesine etkileri üzerine araştırmalar

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.88 6. ÖZET Bu araştırma, ülkemizde sofralık üzümler içinde önemli bir yeri olan Sultaniye Çekirdeksiz çeşidi ile Ege Bölgesinde yetişen Akgemre (Be- yazgemre) cinsi üzümlerin dondurulması ve 6 aylık depolama süresi içinde meydana gelebilecek değişmeleri incelemek amacıyla yapılmıştır. Özdek olarak kullanılan Sultaniye üzümler Manisa, Akgemre çeşidi üzümler ise Narlıdere yöresindeki üretici bağlarından temin edilmiştir. örnekler, sertliği giderilmiş suyla yıkandıktan sonra, danelenmiş- tir. Bu örnekler, plastik (PVC) kaplara doldurulmuş ve kaplar üçe ayrıl mıştır. Bir kısmı %0.1 sitrik asit, %0.1 askorbik asit içeren %30'luk şeker şurubu, diğer kısmı herhangi bir katkı içermeyen %30'luk şeker şu rubu ile tanelerin üstünü örtecek şekilde tamamlanmıştır, örneklerin üçüncü kısmına ise şurup konulmamıştır. Bu şekilde hazırlanan örneklerin her grubu tekrar ikiye ayrılmış ve birinci grup -35°C ortam sıcaklığında 3-8 m/s hava hızında dondurulmuş, diğer grup ise -Zk C'deki derin dondu rucuda yavaş donmaya bırakılmıştır. Donma işlemi tamamlandıktan sonra tüm örnekler -l8°C'deki derin dondurucuda 6 ay depolanmışlardır. Üzümlerde suda çözünür kuru madde, pH, asitlik, leukoantosiyanin, tanen, polifenoloksidaz (P.F.O.) enzimi aktivitesi. Hunter L, a, b, a/b değerleri ile duyusal özellikler (renk, doku, tat ve lezzet), örnek şurup larında da suda çözünür kuru madde, asitlik, pH, askorbik asit (A. A.) analizleri yapılmıştır. Bu analizler, özdekte, dondurulma sonrasında ve 6 aylık depolama süresi boyunca her ay içinde yinelenmiştir. üzümlerin hammadde de ve depolama süresince yapılan analizlerinde çeşitler arasında önemli bir farklılık olduğu belirlenmiştir. Bu farklı lığa çeşit özellikleri yanısıra Akgemre üzümlerinin erken hasat edilme sinin de etkisi olmuştur. örneklerin depolama süresince suda çözünür kuru madde değerlerinin hammaddeye göre artış gösterdiği, bu artışın en fazla şurupsuz olarak dondurulan örneklerde ortaya çıktığı saptanmıştır. Şurup içerisinde don durulan örneklerin şuruplarının refraktometrik kuru maddeleri ise. depo lama süresi boyunca azalmıştır. Buna göre, şurup içerisinde dondurulan89 örneklerde şuruptan, örnekleme ozmatik basıncın da etkisiyle bir geçiş olduğu sonucuna varılmıştır. Dondurulma sonrası 6 aylık depolama süresi içinde belirlenen pH değerlenin artış gösterdiği saptanmıştır. pH'daki en fazla artış yine şurupsuz olarak dondurulmuş örneklerde meydana gelmiştir. Şuruplarda ya pılan pH analizlerinde, katkılı şurupların pH'larında bir azalma gözle nirken, katkısız şurupların pH değerlerinde bir artış ortaya çıkmış ve şurupların pH değerleri depolama süresi sonunda özdeklerin pH değerle rine yaklaşmıştır. Denemeye alınan üzüm örneklerinin hammaddedeki toplam asitlik de ğerleri de, 6 ay sonunda, şurup ilave edilmeden dondurulan örneklerde artarken şurup içinde dondurulan örneklerde azalmıştır, örnek şurupları nın toplam asitlik değerleri ise, saptanan pH değerlerine uygun olarak, katkısız şuruplarda yükselmiş, katkılandırılmış şuruplarda düşmüştür. Her iki çeşit üzüm içinde leukoantosiyanin ve tanen nicelikleri dondurulma işlemi sonrasında bazı örneklerde artış göstermiştir. Ancak 6 aylık depolama süresi sonunda, tüm örneklerin tanen ve leukoantosiya nin nicelikleri azalmıştır. Bu azalmanın en fazla şurupsuz olarak dondu rulan örneklerde meydana geldiği saptanmıştır. Fenolik maddelerdeki bu düşüşlerin renkteki değişim ve polifenol oksidaz enizimi aktivitesi ile negatif ilişkili olduğu belirlenmiştir. örneklerin Polifenol oksidaz (PFO) enzimi aktivitesi dondurulma sonrasında ve depolama süresi boyunca artış göstermiştir. Her iki üzüm çeşidi için de şurup ilave edilmeden iki farklı donma hızında dondurulan örneklerde PFO enzim aktivitesindeki artışın en fazla olduğu belirlen miştir. Katkısız şurup içinde işlenen örneklerin PFO aktivit esinin, %0.1 sitrik asit ve %0.1 askorbik asit içeren şurup içinde dondurulan örneklerin PFO enzim aktivitesinden daha fazla olduğu saptanmıştır. Katkılı şuruplarda enzim aktiviteslnin depolama süresi sonunda daha dü şük olması, askorbik asidin enzim aktivitesini engelleyen olumlu etki sinden kaynaklandığını düşündürmektedir, örnekler dondurulma hızlarına göre incelendiğinde de, hızlı dondurulmanın daha iyi sonuç verdiği belir lenmiştir. Bu da yavaş dondurulma hızlarında hücre zararlanmalarının daha fazla olmasının sonucudur.90 6 aylık depolama süresi içinde sadece örnek şuruplarında incelenen askorbik asit niceliği başlangıçta %0.1 oranında askorbik asit eklenen şurup örneklerinde hızlı bir düşüş göstermiştir. Dane halinde ve homojenize edilen örneklerde kabuk yanında et ren ginin de incelenmesi amacıyla renklerine bakılan üzümlerin Hunter L de ğerleri 6 aylık depolama süresi sonunda hammaddeye göre şurup içinde dondurulan örneklerde, genel olarak, bir artış gösterirken şurupsuz ola^ rak dondurulan örneklerde azalmıştır. Yeşil rengi simgeleyen -a değerle rinin ise, depolama süresi sonunda bir azalma gösterdiği saptanmıştır. Hunter b değerlerinde de, şurupla işlenip dondurulan örneklerde genel o- larak 6 ay sonunda, hammadenin b değerlerine yakın değerler gözlenirken, şurupsuz örneklerde bu değerler azalmıştır. Yeşilin sarıya oranını veren -a/b değerlerininse, şurupsuz örneklerde en düşük olduğu saptanmıştır. Örneklerin Hunter L, -a, b değerleri üzerine uygulanan işlemlerin ve de polama süresinin en fazla etkili olduğu belirlenmiştir. Hammadde, dondurulma ve depolama süresinde duyusal özelliklerde görülen değişmeler panelistlerce belirlenmiştir. Duyusal özelliklerde en iyi sonucu, %0.1 askorbik asit ve %0.1 sitrik asit içeren çözeltiyle işlenerek dondurulan ve depolanan üzümlerden elde edildiği görülmektedir. Katkısız şurupla işlenen örneklerden de olumlu sonuçlar alınmıştır. Şu rupsuz olarak dondurulan üzümler duyusal özellikler bakımından çok kötü düzeyde bulunmuşlardır91 SUMMARY The purpose of this study was to investigate the changes occured during freezing and frozen storage for six month of the grape variaties. namely Sultanas which are well known table grapes in Turkey and Akgemre (Beyazgemre) which are grown in Aegean region. Sultanas were provided from Manisa region, whereas Akgemre variety grapes were provided from Narlxdere region. Samples were separated into berries after being washed with deminerilized water. These samples were filled into P.V.C. containers and those containers were divided into three ports. Sugar syrup at 30° Brix contains 0.1% citric acid and 0.1% ascorbic acid were added into the first group and 30 Brix sugar syrup were added into the second. The thirth sample group were prepared without any addition. These three groups of samples were separated into two parts again and first part was frozen at -35 C with an air velocity of 3-8 m/s. Other group was frozen in a deep freezer at -24 C. After all of the samples were frozen they have been stored for 6 months in a deep freezer at -18 C. Refractometric soluble solid content, pH, acidity, leucoantocyan tannin, Polyphenol oxidase (P. P.O.) enzyme activity, Hunter L, a, b, a/b values were determined and sensorical analysis were performed on berried samples, and refractometric soluble solid content, pH, ascorbic acid, acidity analysis were applied on syrups. These analysis were also made in raw material, after freezing and throughout the whole storage period, monthly. Significant differences were determined between the varieties of grapes. The sources of the differences were related to the varietlcal properties, furthermore it was found that the earlier harvesting of Akgemre grapes caused an effective changes in almost all of the properties examined. It was found that refractometric soluble solid content of the grapes increased during the storage period. The amounth of the increase reached to its highest value in the samples which were frozen without92 ayrup. The refractometric soluble solid content of syrups decreased during the storage period. It was concluded that the increase of the water soluble solid contents of the samples which have been frozen in sugar syrup may be related with their osmotic pressure. It was shown pH values increased after frozen storage for 8 months. The highest increase in pH values demonstrated in the samples frozen without syrup. According to the pH analyses, it was found out that pH of added syrups were decreasing, where as pH value of plain syrups were increasing. At the end of the storage period pH of the syrups approached to the pH of the original samples. Total acidity values of samples frozen without syrup increased, while it decreased in the samples frozen with syrup at the end of six months storage period. The total acidity of 30 Brix sugar syrups increased and the total acidity of added syrups decreased, depending on their pH values. In both of the varieties of grapes, leucoantocyanin and tannin contents decreased significantly during the storage period. The highest decrease in polyphenols took place in the samples frozen without syrup. These decreases in phenolic substences were closely releated with P P 0 activities and also with the changes of colour. P P 0 activities of samples increased after freezing and during the storage period. The highest values for both varieties were found in the samples of grapes frozen without syrup and frozen with both two diferent freezing rates. Samples frozen in 30° Brix sugar syrup had a higher P P 0 activity than the samples frozen in added sugar syrup. At the end of storage period P P 0 activity of the samples with added syrup was less than the other samples. It was concluded that this result was obtained, because of the existances of ascorbic acid since it affected on the enzyme activity. It was found that higher freezing rates gave lower enzyme acti vites. This may be caused by the cell damage occurred during lower freezing rates when comparied to higher rates.93 According to the analysis applied on the sample syrups the ascorbic acid content which was 0.1% initialy, decreased throughout the storage period. It was established that preperation method and storage period were most effective on the Hunter L, a, b and a/b values. The changing in sensorical properties of samples on the raw material, freezing and during the frozen storage were established by panelists. Samples frozen in 0.1% ascorbic acid and 0.1% citric acid added syrup gave best results for the sensorical properties. Samples frozen in 30° Brix sugar syrup gave good results too. Samples frozen without syrup were evaluated as poor or very poor on their sensorical properties during the storage period. C. ***£2££

Airborne fungi in a Turkish olive processing plant

2nd SAFOODNET Workshop on Microbiological Risk Management in Food Processes; Lyngby; Denmark; 13 October 2008 through 15 October 2008Studies employing gravity settling culture plates (GSC) were conducted in order to analyse the airborne fungi of an olive processing (ripe pitted, natural calamata pitted and whole olive) plant in Izmir, Turkey, in May 2008. Sampling procedure for airborne fungi was performed 8 times during the processing. Numbers and types of airborne fungi in the air of olive processing areas were investigated by exposing a Petri dish of malt extract and potato dextrose agar medium for 15 min and then counting the number of colonies which develop after incubation at 25°C for 7 d.. Moulds were identified according to Pitt and Hocking (1997) and Samson et al. (1996)

Optimization of ohmic heating applications for pectin methylesterase inactivation in orange juice

WOS: 000341701700015PubMed ID: 25190836Ohmic heating (OH) which is among to electro-thermal methods and helps to inactivate microorganisms and enzymes was used in this study as thermal treatment on orange juice production for pectin methylesterase (PME) inactivation. Response surface methodology (RSM) was used for optimization of OH conditions. The effects of voltage gradient and temperature (independent variables) were investigated on PME activity (response) of orange juice. After optimization orange juice was produced and compared with untreated control juices and conventional thermally heated juices on the aspect of PME inactivation and some quality characteristics. Reduction of PME activities was found approximately 96 % in OH groups where conventional thermally heated juice has 88.3 % reduction value. Total pectin content was increased 1.72-2 % after OH applications. Ascorbic acid contents of OH samples were found between 43.08-45.20 mg/100 mL where conventional thermally heated juice has 42.9 mg/100 mL. As a result, it was determined that OH can be applied as a thermal treatment on orange juice production in moderate temperatures for PME inactivation and may improve functional properties of orange juice.Gaziosmanpasa University (Tokat-TURKEY)Gaziosmanpasa University; MEYED (Meyve Suyu Endustrisi Dernegi), Ankara/TURKEYFinancial support for this research (scientific research project) was provided by Gaziosmanpasa University (Tokat-TURKEY) and MEYED (Meyve Suyu Endustrisi Dernegi), Ankara/TURKEY. The authors wish to thank to Assoc Prof. Filiz Icier and Hayriye Bozkurt (MS) for their help during study

Inactivation effect of microwave heating on pectin methylesterase in orange juice

WOS: 000443647500002Introduction. Enzyme inactivation is a major objective in orange juice production. Conventional heating in elevated temperature causes adverse effects on the final products such as color alterations, flavor damages, ascorbic acid losses. For this, microwave heating (MW) was used in this study as thermal treatment on orange juice production for pectin methylesterase (PME) inactivation, and response surface methodology (RSM) was used for optimization of MW conditions. Materials and methods. Oranges (Citrus sinensis Osb.) of Navel variety were used as raw material in this study. The effects of flow rate and power on PME activity were investigated. After optimization orange juice was produced with using optimized conditions and compared with untreated control juices and conventional thermally heated juices on the aspect of PME inactivation and some quality characteristics. Results and discussion. The linear effects of flow rate (x(1)) and power (x(2)), as well as the quadratic effect of flow rate (x(1)(2)), power (x(2)(2)) and the interaction effect of flow rate-power (x(1),x(2)) were significant for PME inactivation by MW. Lack of fit of experimental data was not significant (P>0.05) for model. The coefficient of variation (C.V.) was 6.27%. The model showed an adequate precision of 6.788x10(-3). The determination coefficient (R-2) was 0.9793, while the adjusted determination coefficient (adjusted R-2) value was 0.9645. R-2 and adjusted R values for the models did not differ dramatically indicating non-significant terms have not been included in the model. Reduction of PME activities was found approximately 93-95% in MW groups. The PME inactivation rate was described satisfactorily as a function of microwave heating conditions. The PME can be inactivating in moderate temperatures by MW (40 mL/min-900W-83 degrees C) and MW (50 mL/min-900W-75 degrees C). D values were calculated for two optimum conditions of MW and CH treatments and found as 39.24 sec for MW (40 mL/min-900W), 38.76 sec for MW (50 mL/min-900W) and 70 sec for CH (95 degrees C-60 sec). Total pectin content was increased 17.2% after MW application. And the loss of ascorbic acid content for MW sample was found lower than other applications. Conclusions. A synergistic effect of microwave energy and temperature on orange juice PME inactivation was found under microwave heating conditions. It was determined that MW (50 mL/min-900W) can be applied as a thermal treatment on orange juice production in moderate temperatures (75 degrees C) for PME inactivation and may improve functional properties of orange juice. And this result is extremely important in terms of cloud stability of orange juices.Gaziosmanpasa University (Tokat-Turkey)Gaziosmanpasa University; MEYED (Meyve Suyu Endustrisi Dernegi), Istanbul/TurkeyFinancial support for this research (scientific research project) was provided by Gaziosmanpasa University (Tokat-Turkey) and MEYED (Meyve Suyu Endustrisi Dernegi), Istanbul/Turkey