Farklı ambalaj malzemelerinin ve depolama sıcaklıklarının çiğ ve kavrulmuş fındıkların kalitesi üzerine etkileri
The effect of different packaging materials and storage temperatures on the quality of naturel and roasted hazelnuts
Yazar: OSMAN EROĞLU
Danışman: PROF. DR. GÜRBÜZ GÜNEŞ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Gıda Mühendisliği Ana Bilim Dalı / Gıda Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: Gıda Mühendisliği = Food Engineering

Özet:
Fındık bademden sonra sert kabuklu meyveler arasında yetiştiticiliği en fazla yapılanıdır. Dünyada son beş yıl baz alındığında yaklaşık 936 bin hektarlık alanda fındık üretimi yapılmaktadır. Türkiye bu dikili alanların yaklaşık %76'sına sahiptir. Türkiyenin ardından sırasıyla %8 ile İtalya ve %3 ile Azerbaycan gelmektedir. Dünya fındık üreretimi son beş yıllık üretimler baz alındığında ortalama 836 bin tondur ve bunun %66'sı Türkiye'de gerçekleşmektedir. Görüldüğü gibi fındık yetiştiriciliği ve üretimi Dünyada en fazla olan ülke Türkiye'dir.
Bu çalışmada Türkiye'de yetiştiriciliği yapılan ve ihracatta en fazla paya sahip Giresun kalite (tombul), mahsül yılı 2018 olan fındıklar kullanılmıştır. Fındıklar çiğ (natürel) ve kavrulmuş olarak iki farklı yapıda incelenmiştir. Fındıklar 5 farklı yapıya sahip laminasyonlu plastik ambalajlarda Modifiye Atmosfer altında (O2<%2, N2>%98) 150 g'lık olacak şekilde ambalajlanmıştır. Bu çalışmada kullanılan ambalaj materyalleri; polietilentereftalat/ polietilen (PET/PE), polietilentereftalat/ orientedpoliamid/ polietilen (PET/OPA/PE), polietilentereftalat/ alüminyum/ polietilentereftalat/ polietilen (PET/AL/PET/PE), polietilentereftalat/ alüminyum/ polietilen (PET/AL/PE), polietilentereftalat/ alüminyum/ polietilentereftalat/ polietilen (PET/*AL/PET/PE) şeklinde olup farklı kalınlıklardaki lamine ambalajlardır. Kullanılan ambalajlardan bariyer özelliği en az olan (PET/PE) için hava ortamında da ambalajlama yapılarak Modifiye Atmosfer (MA) ile ambalajlanan aynı çeşit ambalaj ile mukayese edilmiştir. Çiğ ve kavrulmuş fındık ambalajlarının üçte biri 10ºC, RH %48±8 depoda üçte biri 20ºC, RH %65±5 ve diğer kısmıda 30ºC'lik RH %65±5 aralığında test kabinlerinde karanlık ortamda 36 hafta süre ile depolanmıştır. Örneklerin başlangıç aşamasında ve depolama süresi boyunca 4., 8., 12., 16., 20., 24. ve 36. haftada yapılan analizlerde fiziksel, kimyasal ve duyusal özellikleri incelenmiştir. Analiz sonuçlarının değerlendirilmesi için SPSS 25 istatistik paket programında (3 sıcaklık x 6 işlem x 8 zaman x 3 tekerrür) faktöriyel düzende varyans analizi yapılmıştır. Yapılan varyans analizi sonucunda faktör düzeyleri arasında farklılıkların tespiti için Duncan çoklu karşılaştırma testi kullanılmıştır. 
Depolama süresi sonunda kavrulmuş ve çiğ fındıkta en yüksek nem değeri sırası ile, 30ºC'de PET/PE (H) ambalajında %3.24 ve 10ºC'de PET/AL/PET/PE ambalajda %5.40 olarak ölçülmüştür. En yüksek su aktivite değeri kavrulmuş fındıkta 30ºC'de PET/PE ambalajda 0.5943 ve çiğ fındıkta 30ºC'de PET/AL/PET/PE (MA) ambalajında 0.7333 olarak ölçülmüştür. En yüksek serbest yağ asitliği değeri kavrulmuş fındıkta 30ºC'de PET/PE (MA) ambalajında %0.40 (oleik asit), çiğ fındıkta PET/*AL/PET/PE (MA) ambalajında 30ºC'de %2.09 (oleik asit) ölçülmüştür. Enyüksek peroksit sayısı kavrulmuş fındıkta 30ºC'de PET/PE (MA) ambalajında 1.17 meq O2/kg, çiğ fındıkta 20ºC'de PET/PE (MA) ambalajında 1.22 meq O2/kg olarak ölçülmüştür. Tepe boşluğu %O2 oranı kavrulmuş fındıklarda en yüksek değer 10ºC'de PET/PE (MA) ambalajında %17.4 ve çiğ fındıkta 10ºC'de PET/PE (MA) ambalajındada %16.0 olarak ölçülmüştür.
Kavrulmuş fındık örneklerinin MA'de (O2<%2, N2>%98) 36 haftalık depolama süresi sonunda fiziksel, kimyasal ve duyusal özelliklerinin korunması için Alüminyum içerikli ambalajların diğer ambalaj materyallerine göre daha iyi sonuç verdiği saptanmıştır. Bariyer özellikleri düşük ambalaj malzemeleri ile ambalajlanan kavrulmuş fındıkta zaman ve sıcaklık artışının kalite özelliklerini olumsuz etkilediği görülmüştür. 3 farklı yapıdaki Al içerikli ambalajın depolama süresi sonunda kavrulmuş fındıkların kalite özellikleri değişimine etkisi farklılık göstermemiştir. Çiğ fındıkta, tüm ambalaj malzemeleri ile ambalajlanan örneklerin kalite özelliklerini 36 haftalık depolama süresi sonunda 10ºC, RH %48±8'deki depolama şartlarında koruyabildiği ancak 20º ve 30ºC'de RH %65±5'te koruyamadağı görülmüştür. PET/PE ambalaj malzemesi ile Modifiye Atmosfer (MA) (O2<%2, N2>%98) ve Hava (H) ortamında ambalajlamanın 36 haftalık depolama süresi sonunda kavrulmuş ve çiğ fındıkların kalite özellikleri değişime etkisi önemli bulunmamıştır.

Abstract:
Hazelnut is a fruit of Corlyus avellana L. Family and its homelands known as Anatolia. The highest quality hazelnut of the World have been picked up and grown in Anatolia.
Turkey is the main hazelnut producer in the world (approximately 650 000 MT in 2001, unshelled basis), contributing approximately 70% of the total global production, followed by Italy (about 130 000 MT/year), the U.S. (about 45 000 MT/year), and Spain (about 25 000 MT/year). The Black Sea Region accounts for % 74.8 of the overall hazelnut production area and % 72.5 of overall production in Turkey. Hazelnut is one of the major traditional export product having an outstanding position in our national economy and agriculture. Turkey's total export revenue from hazelnut and hazelnut products is approximately one billion U.S. dollars annually.
In production of chocolate, confectioneries, baking products and ice cream, hazelnut can be used industrially or it can be consumed as a fruit as well, not subjected any process. In a number of popular foods, hazelnut is widely used as taste, aroma and flavor giving ingredient. % 80 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.
Hazelnut plays a major role in human nutrition and health among nut species, because of its special fatty acid composition, which includes oleic, and linoleic acids as well as the presence of tocopherols and sterols. Hazelnut provides an excellent source of energy due to its high oil content of approximately 60%. Several research groups have reported the benefits of inclusion of nuts in the human diet. These effects could be related to the fatty acid profile of hazelnut oil which is rich in MUFA and PUFA. Studies have shown that diets low in saturated fat and high in MUFA are effective in controlling blood lipid levels, a likely consequence of which may be rendering beneficial effects on the risk of CHD. In addition, diets rich in MUFA (high in hazelnut oil) exert positive effects in the reduction of blood pressure, reduction of mean total CHOL, decrease of LDL CHOL, increase of HDL CHOL, and decrease of blood TAG in humans. Tocopherols are particularly important in hazelnut oil because they have a nutritional function for humans as vitamin E and display antioxidant activities in vivo and in vitro; R-tocopherol has the highest vitamin E activity. In addition, tocopherols in association with polyphenols and other substances, contribute to the stabilization of hazelnut oil and their quantity may reflect the oxidative state of the oil.
Fats and oils oxidative stability depend on their environment, and there are differences in their rate of oxidation in the bulk vs o/w (oil-in-water) emulsions. Lipid oxidation negatively affects the flavor, odor, color, and nutritional value of foods during storage, and this may also limit the utilization of hazelnut oil in processed and fortified foods as well as nutritional supplements. It is, therefore important to evaluate the oxidative stability of hazelnut oil as affected by processing and storage conditions.
Hazelnuts are typically consumed as whole nuts (raw or roasted) or as ingredient for confectionary and bakery industries as they are highly appreciated for their typical taste, aroma and crunchy texture. An industrial roasting process is applied to remove the hazelnut skin, to reduce the moisture and to develop the unique sensory features. Thermal treatment of nuts in roasting processes leads to changes in the carbohydrates, proteins, fats or physiologically active substances, such as vitamins or essential amino acids in accordance with the temperature–time treatment of the product. Additionally, roasting is often used to extend the nuts shelf life due to the inactivation of the oxidative enzyme system. Enzymatic activity plays a significant role in hazelnut preservation. Free fatty acids are released from triglycerides under the effect of moisture through lipases. Free fatty acids is a significant criterion in determining the quality of hazelnut, which effects the taste of hazelnut on its own. Free fatty acid causes a bitter taste and soapy aroma in hazelnut. Lipase activity depends on factors such as moisture, water activity, temperature and ph. It is very important for hazelnut to contain low moisture level at the initial stage of storing and during the storage period so that no loss of quality occurs in hazelnut, since enzymatic reactions are triggered in high moisture environments and deterioration accelerates. (Lipoxygenic enzymes) and the formation of reaction products, which exhibit antioxidant activity. Although favorable for many aspects, roasting can also lead to a number of physical and chemical changes, such as microstructural and lipid modifications, which might increase the sensitivity of the product to oxidation and, hence, reduce its shelf life.
In this study, with the largest share in exports in Turkey grown and Giresun quality hazelnuts it is used in the 2018 crop. Hazelnuts were examined in two different structures as raw (natural) and roasted. Hazelnuts are packaged in laminated plastic packages of 4 different structures in a modified atmosphere of 150 grams. Of the packages used, packaging with atmospheric environment was made with the least barrier property. It was compared with the same kind of packaging packaged with Modified Atmosphere Packaging (MAP). One third of raw and roasted hazelnut packs were stored at 10 ºC, one third at 20 ºC and the other part at 30 ºC in dark storages with RH 55-70% and stored for 36 weeks. At the same time, sensory evaluation of hazelnuts was made by sensory panel. In the 3-replicate analysis of the samples at the initial stage and during storage at 4, 8, 12, 16, 20, 24, 36 weeks; Moisture values, water activities (aw), free fatty acidity (FFA) (% oleic acid), peroxide numbers (meq O2/kg), color values (L, a and b),%O2 in the headspace of the packages were examined. In order to evaluate the results of the analysis, variance analysis was carried out in factorial order in SPSS 25 statistical package program (3 temperature x 6 packaging x 8 time). Duncan multiple comparison test was used in PostHoc analysis which was used to determine which averages differ from each other as a result of variance analysis. The packaging materials used in this study are polyethylene terephthalate / polyethylene (PET / PE), polyethylene terephthalate / oriented polyamide / polyethylene (PET / OPA / PE), polyethylene terephthalate / aluminum / polyethylene terephthalate / polyethylene (PET / AL / PET / PE), polyethylene terephthalate / aluminum / polyethylene (PET / AL / PE), in the form of polyethylene terephthalate / aluminum / polyethylene terephthalate / polyethylene (PET / *AL / PET / PE) and laminated packages of different thicknesses. 
Initially, the roasted hazelnut had a moisture content of 1.75%, water activity of 0.3717, free fatty acid of 0.28% of oleic acid, peroxide number of <0.01 meq O2 / kg, color values of L, a and b as 67.69, 4.54, 22.45 respectively and % O2 value of the packets It was measured less than 2%. In raw (natural) hazelnuts; moisture value 5.13%, water activity 0.6772, free fatty acid 0.43% oleic acid, peroxide number 0.02 meq O2 / kg, color values L, a and b respectively 60.90, 3.56, 15.63 and O2% in the headspace of the packets was measured to be less than 2%.
The highest moisture content in roasted and raw hazelnuts after storage period was measured as 3.24% in PET / PE packaging at 30 ºC and 5.40% in PET / AL / PET / PE packaging at 10 ºC, respectively. The highest water activity value was measured as 0.5943 in roasted hazelnut in PET / PE packaging at 30 ºC and 0.7333 in PET / AL / PET / PE packaging in raw hazelnuts at 30 ºC. The highest acidity and peroxide values were measured as 0.40% oleic acid and 1.17 meq O2 / kg in roasted hazelnuts at 30 ºC in PET / PE packages, respectively, in raw hazelnut, it was measured as 2.09% oleic acid in PET / *AL / PET / PE packaging at 30 ºC and 1.22 meq O2 / kg in PET / PE (MA) packaging respectively. Headspace O2% values of roasted hazelnuts highest value in PET / PE packaging at 10 ºC 17.4% and raw hazelnut at 10 ºC in PET / PE packaging was measured as 16.0%.
At the end of 36 weeks storage period of roasted hazelnut samples, it was found that aluminum containing packages gave better results than other packaging materials in order to maintain their physical, chemical and sensory properties. It has been observed that the increase in time and temperature adversely affect the quality properties of the roasted hazelnuts packaged with low barrier properties packaging materials. For roasted hazelnut samples, it was observed that aluminum containing packaging materials have different layer number and thickness and that it was not important in terms of preserving physical, chemical and sensory properties of hazelnuts at the end of storage period. In raw hazelnut, it was observed that the quality characteristics of samples packaged with all packaging materials were maintained at 10ºC, RH 48 ± 8% storage conditions at the end of 36 weeks storage period, but not at 65 ± 5% RH at 20º and 30ºC. After 36 weeks storage period of PET / PE packaging with Modified Atmosphere (MA) (O2 <2%, N2> 98%) and Air (H) environment, the effect of raw hazelnuts on quality characteristics change was not significant. In general, low temperature storage of roasted and raw nuts has been shown to have a positive effect on shelf life.