Bazı küflerin fındıkta lipolitik aktivitesinin incelenmesi
Başlık çevirisi mevcut değil.
- Tez No: 75267
- Danışmanlar: PROF. DR. DİLEK HEPERKAN
- Tez Türü: Yüksek Lisans
- Konular: Gıda Mühendisliği, Food Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Gıda Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 124
Özet
ÖZET Fındık ulusal ekonomimizde ve taamımızda önemli bir yer tutan geleneksel ihraç ürünlerimizdendir. Ülkemiz için ekonomik öneme sahip olan findik aynı zamanda bileşenleri nedeniyle önemli bir besin kaynağıdır. Bu nedenle fındıkların kalitelerini kaybetmeden muhafazası oldukça önemli olup çalışmamızda bu amaca yönelik olarak fındık materyal seçilmiştir. Fındıkların haşatından tüketimine kadar geçen her aşamada küflerin faaliyetleri söz konusudur. Fındıkta küflerin faaliyetleriyle oluşan lipaz enzimi nemli ortamda, %60- 70 gibi yüksek oranda yağ içeren Andıklarda hidrolize neden olur. Fındık yağındaki trigliseridlerin parçalanarak serbest yağ asidlerinin (FFA) açığa çıkması findıkta acılaşmaya, böylece fındığın tad ve aromasının bozulmasıyla kalite kayıplarına yol açmaktadır. Çalışmamızda materyal olarak seçilmiş findik Karin Gıda San. ve Tic. A.Ş.'den temin edilmiş olup, fındık mikroflorasında yaygın olarak karşılaşılan Aspergillus flams, Aspergillus niger ve Penicillium olsoni cinsi küflerin 30°C sıcaklık ve %80, 85 ve 90 bağıl nem ortamlarındaki lipolitik aktiviteleri incelenmiştir. Küf sporları ile aşılanmış findik numuneleri, doymuş tuz çözeltileri ile ayarlanmış farklı bağıl nem ortamlarındaki kavanozlara yerleştirilerek etüvde 28 gün süreyle depolanmıştır. Depolama sürecinde belli sürelerde alman findik numunelerinde nem, pH, FFA, trigliserid (TG), 1-3 digliserid (1-3DG), 1-2 digliserid (1-2DG) ve monogliseridler (MG) saptanmıştır. Aynı işlemler findik numunelerine belirli bir miktar su ilave edilerek tekrarlanmış olup, bu kez aşılanmış findik numuneleri boş kavanozlar içine yerleştirilmiştir. Çalışma sonunda lipolitik aktiviteye en fazla sahip olan küflerin sırasıyla Aspergillus niger, Aspergillus flavus ve Penicillium olsonii olduğu tespit edilmiş olup, %90 bağıl nem ortamında hidrolizin %80 ve 85 bağıl nem ortamlarına göre çok hızlı gerçekleştiği belirlenmiştir. Buna karşılık nemi arttırılmış findik numunelerinde küflerin lipolitik aktivitelerinin %90 bağıl nem ortamından daha fazla olduğu görülmüştür. %90 bağıl nem ortamında depolama süresi sonunda FFA başlangıç değeri olan %0.4'den yukarıdaki küf sırasına göre %90.98, %62.07, %33.76 değerine yükselmiş, TG ise bunun aksine %9.02, 37.93, 66.24'e azalmıştır. Fındıkta pH değerindeki azalma küf türlerine göre farklılık göstermiş, depolamadaki bağıl nem değerinin önemli etki yaptığı görülmüştür. %90, %85 ve %80 bağıl nemli ortamlarda 1 aylık depolama sonunda Aspergillus niger aşılanmış fındıklarda 6.40'nin üzerinde olan pH değeri sırayla 3.21, 5.44, 6.24; Aspergillus flavus aşılanmış Andıklarda 4.51, 6.23, 6.20; Penicillium olsonii aşılanmış Andıklarda 4.84, 6.25 ve 6.21 olarak saptanmıştır. ıx
Özet (Çeviri)
SUMMARY A STUDY OF LIPOLYTIC ACTIVITIES OF SOME MOULDS IN HAZELNUT Key Words : Hazelnut, lipase, hydrolysis, Free Fatty Acid(FFAJ, Aspergillus niger, Aspergillus flavus, Penicillium olsonii. Hazelnut is a fruit of Corlyus avellana L. family and its homeland is known as Anatolia. The highest quality hazelnuts of the world have been picked up and grown in Anatolia (DURUOGLU et al 1980). The biggest hazelnut producer and exporter in the world is Turkey while Germany is the major importing country (ANON, 1996). Turkey is the leading country in production of hazelnut followed by Italy and Spain (KTNDERLERER and JOHSONJ992). The Black Sea Region accounts for 74.8% of the overall hazelnut production area and 72.5% of the overall production in Turkey (EKE and GOKTAN,1987). In the production and processing of hazelnut, 8 million people are actively involved (OZDEMIR, 1997). In this context, hazelnut is one of the major traditional export product, having an outstanding position in our national economy and agriculture. Hazelnut can be used industrially in production of chocolate, confectioneries, baking products and ice cream or it can be consumed as a fruit as well, not subjected to any process. Hazelnut is widely used as taste, aroma and flavour giving ingredient in a number of popular foods. 80%o of the unshelled hazelnuts are used in the production of chocolate, 15% in sugar, biscuits and cake production, and remaining 5% is consumed as is without being processed (OZDEMIR, 1997). In addition to being our traditional export product having a special place in our national economy and agriculture, hazelnut is at the same time an important source of nutrition in terms of its natural composition. The most important nutritive elements contained in hazelnut are fat, protein, carbohydrates, vitamin Bl, B2 and E, and minerals. Fat content is the highest. Hazelnut oil is a vegetable oil with high nutritive values (PALA et al 1996). Various researchers have reported different values regarding the fat ratio and fatty acids. GARCIA et al (1993) has determined the fat ratios and fatty acid compositionsof the fruits of 10 different hazelnut types one by one and found that the fat content was between 54.8% and 71%, and the percentage of oleic acid in 100 g 75.2 and 84.2%. Whereas, ANITA et al (1994) has reported a fat ratio of 48-72% and that oleic acid had the highest value in percentage among fatty acids as 70-80%. On the other hand, KINDERLERER and JOHSON (1992) has reported that the oleic acid amount was 75 gr/100 g, while PALA et al (1990) had found this figure as 90.71 g/100 g. It has been reported that a diet enriched with hazelnut with a high percentage of mono unsaturated fatty acid like oleic acid did not give rise to an important change in the carbohydrate metabolism which was the case with high carbohydrate diet, but it had a favourable effect on plasma, lipid and lipoproteins. Thus, it has been concluded that hazelnut may well be used in diets of diabetics who are not dependent on insulin (PALAetal 1996). Hazelnut is used as kernels, particularly roasted kernels in the food sector For example, hazelnut used as dried fruits passes through the following stages: picking, initial drying, peeling of outer soft shells, second drying, shell breaking, separation of mouldy and crushed ones, classification, roasting, packaging and storage (HEPERKAN, 1996). Any deterioration likely to occur during such stages are grouped into three as physical, chemical and microbiological spoilage. Physical spoilage turns hazelnut into a condition susceptible to chemical and biological spoilage. Physical spoilage results in quality degradation but is- not as significant as chemical and microbiological ones. The kernel moisture of food substances and their moisture exchange with the prevailing environment are physical processes and quality criteria making further spoiling easier. While green, hazelnut contains water of 50% or more by weight. After drying, water content may drop down to 3%. On the other hand, commercially hazelnuts should have a moisture of 6% for kernels and 8% for shelled hazelnuts. The low moisture level of hazelnuts is of great importance as far as the quality maintenance is concerned during the pre- storage, processing and storage stages, because in high moisture environments, enzymatic reactions initiate resulting in a rapid spoiling. In cases where the ambient relative humidity exceeds 70%, moulds rapidly develop resulting in a fast quality degradation. On the other hand it is known that the enzymes can be active in an ambient relative humidity between 60-70%. The relative humidity corresponding to a moisture content of 6% in hazelnuts is 80% in sorption isotherms of hazelnuts. Under this relative humidity condition, enzymes activate and moulds develop. A relative humidity of 70% corresponds to a moisture content of 5% in hazelnuts. Given the extremely short storage period of kernels even under most favourable conditions, it has been reported that for a successful storage, the ambient temperature should be between 0-4°C and relative humidity should not exceed 70% (BAS, 1990). The concentration of oil in the hazelnut composition as high as 60-70% by weight has a great importance in storage and processing. The spoilage occurring in hazelnut is mostly caused by the high ratio of fat they contain just like any other fatty food. In the presence of air oxygen, hazelnut kernels become rancid if stored under room temperature conditions. As a result of the reaction with oxygen of the unsaturated xifatty acids in hazelnut oil, rancidity occurs and eventually the natural aroma of hazelnut reveals unpleasant taste, aroma and flavours. The shelf life of hazelnut is impaired by the activity of lipase enzyme formed by moulds as a result of catalytic reactions or microbial contamination (KINDERLERER and JOHSON 1992). The complex mixtures of the compounds released as a result of the oxidation of the unsaturated fatty acids found in hazelnut oil can also be produced by the metabolic activities of the micro-organisms. An important portion of hazelnut microflora is moulds. At all stages from harvesting to consumption, activities of moulds continue. EKE (1996) has studied the microflora and the formation of aflotoxin. These hazelnuts have been obtained from the tree itself, from the sun-drying field and from the storage area. The types of moulds that form microflora in hazelnut are Aspergillus, Penicillium, Eurotium, Tricothecium, Cladosporium, Rhizopus and Trichoderma. It has been reported that Trichothecium roseum was the most commonly found one in hazelnut, followed by Aspergillus flavus, Penicillium cornmun, Eurotium spp, P. brevicompactum, P. crustosum, P. janczewskii, A. niger, A. versicolor, Tricoderma harzianum, Cladospontum spp. and Rhizopus spp. As a result of being commonly present in hazelnut, in our study, lipolytic activities of Aspergillus flavus, A. niger, and P.olsonii moulds have been examined. Due to the development in the convenient ambient atmosphere, moulds produce lipase, releasing free fatty acids and spoiling the hazelnut. Lipase enzyme belongs to the lipoxidase group enzymes, which has important and wide application commercially. Lipases are commonly found in the nature. We can classify lipases into three groups as to their sources as animal, vegetal, and microbial. As a result of storage in inappropriate relative humidity and temperature conditions, mould activities release lipase enzyme, which in turn hydrolyses the triglycerids found in hazelnut oil, increasing the amount of free fatty acids and causing hazelnut to get rancid, the shelf life to be dramatically shortened and giving rise to quality degradation. The hydrolysis of the hazelnut oil with the lipase enzyme takes place as follows: Triglycerids + 3 mol water < glycerol + fatty acid The hydrolysis reaction is a recycling reaction, which takes place during the water and oil phase. Hazelnut used as the testing material in our study has been obtained from M/S Karin Gida Sanayi & Ticaret A. S. After the lypolytic activities of A. flavus, A. niger and P.olsonii moulds isolated from the hazelnut have been determined in a synthetic feeding environment containing tributyrin, the juices found to have formed lipase have xnbeen used in the inoculation study. Thus, the lypolytic activities of Aspergillus flams, Aspergillus niger and Penicillium olsonii type moulds have been examined at an ambient temperature of 30°C and at RH of 80%, 85% and 90%. The spor suspensions of 106 conidia/ml of these three moulds have been prepared and 50 g of the sterilised hazelnut samples have been inoculated with 1 ml of the spor suspensions. The hazelnut samples so inoculated have been placed in jars in differing relative humidity conditions (80%, 85% and 90%) containing saturated salt solutions, and have been stored in an oven at 30°C for 28 days. During the storage period, hazelnut samples have been taken and moisture, pH, free fatty acids (FFA), triglycerids (TG), 1-3 diglycerid (1-3DG), 1-2 diglycerid (1-2DG) and monoglycerids have been determined. The same process has been repeated by adding some water into the samples to increase the amount of moisture. During this study, it has been determined that the moulds that have the highest level of lypolytic activity were Aspergillus niger, Aspergillus flavus, and Penicillium olsonii respectively and hydrolysis occured more rapidly at RH 90% than at RH 80% and RH 85%o. At the end of the storage period the FFA value being 0.4% at the beginning at RH 90% has risen to 90.98% for Aspergillus niger, to 62.07% for Aspergillus flavus and to 33.76% for Penicillium olsonii, whereas TG values being 100 at the beginning has decreased to 9.02%, 37.93%, and 66.24% respectively. The decrease in the pH level has changed depending on the mould types, and the RH value during the storatge period had a significant impact on this difference. At the end of 1 month storage period at RH90%, 85% and 80%, pH value being over 6.40 has been determined to have changed to 3.21, 5.44 and 6.24 respectively in A. niger inoculated hazelnuts; 5.31, 6.20, 6.21 in A. flavus inoculated hazelnuts, and 4.51, 6.25 and 6.21 in P. olsonii inoculated hazelnuts. While the change in pH values were quite low at RH 80% and 85%, it was very sharp at RH 90%, and due to organic acids formed by the moulds, at the end of storage period, the pH value being 6.69 at the beginning has dropped to 3. 18, 5.31 and 4.84 in the same as mentioned above. Decrease in TG's or an increase in FFA' s is an indirect result of enzymatic hydrolysis of hazelnut oil which reflects lipolytic activity. Therefore the relation between the storage period and the pest hydrolysis released FFA has been studied for each mould. Figure 1 and 2 indicate the relationship between the period and FFA, as well as the relationship between the period and pH for Aspergillus niger at RH 80%, RH 85% and RH 90%. Figure 3 and 4 indicate the relationship between the period and FFA, as well as the relationship between the storage period and pH for Aspergillus flavus at RH 80%, RH 85% and RH 90%. Figure 5 and 6 indicate the relationship between the storage period and FFA, as well as the relationship between the storage period and pH for Penicillium olsonii at RH 80%, RH 85% and RH 90%. As could be seen in these figures, the increase in FFA for each mould studies at RH 90%) is higher than those at 80% and 85%, and similarly, the decrease in pH is greater at RH 90% as compared to RH 80% and 85%. _ Xlll-.- %80 Relative Humudity -a- %85 Relative Humudity -A- %90 Relative Humudity Storage time, day Figure 1. Relationship between the storage period and FFA for Aspergillus niger at RH 80%, RH85% and RH 90%. 6 10 Storage time, day 20 -?- pH %80 Relative Humudity -H- pH %85 Relative Humudity -A- pH %90 Relative Humudity 28 Figure 2. Relationship between the storage period and pH for Aspergillus niger at RH 80%, RH85% and RH 90%. XIV6 16 Storage time, day 24 28 - FFA %80 Relative Humudity - FFA %85 Relative Humudity - FFA %90 Relative Humudity Figure 3. Relationship between the storage peiiod and FFA for Aspergillus flaws at RH 80%, RH85% and RH 90%. 6 10 Storage time, day -pH %80 Relative Humudity - pH %85 Relative Humudity - pH %90 Relative Humudity Figure 4. Relationship between the storage period and pH for Aspergillus flovus at RH 80%, RH85% and RH 90%. xv-FFA %80 Relative Humudity ? FFA %85 Relative Humudity - FFA %90 Relativy Humudity 10 16 Storage time, day Figure 5. Relationship between the storage period and FFA for Penicillhim olsonii at RH 80%, RH 85% and RH 90%. -?- pH %80 Relative Humudity -a- pH %85 Relative Humudity -A- pH %90 Relative Humudity 10 16 Storage time, day Figure 6. Relationship between the storage period and pH for Penicillium olsonii at RH 80%, RH 85%, and RH 90%. In conclusion, in this study the lipolytic activities of A. niger, A. flams and P. olsonii have been examined at certain temperatures and relative humidity conditions, and thus the factors having impact on the spoilage of moulds have been studied. xvi
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