Çikolatalı Draje Yapımında Uygulanan Farklı İşlemlerin Rafömrü Üzerine Etkileri

Abstract

Bu çalışmada üç ayrı tipte kaplama materyali (sütlü, bitter ve beyaz çikolata) kullanılarak özel olarak hazırlanan çikolatalı fındık draje örneklerinin yansına cilalama olarak tabir edilen gum arabik ve şellak solüsyonu tatbik edilirken; diğer yarısına tatbik edilmemiştir. Örnekler, doymuş tuz çözeltisi ile hazırlanan serin depo ortamında (3 °C ve % 60 BN) ve ortam şartlarında (~ 18-20 °C ve % 60-70 BN) iki ay depolanmıştır. Depolama başlangıcında kullanılan çikolataların, dolgu materyalinin (kavrulmuş fındık) ve kaplama tabakasının genel özellikleri analitik olarak saptanmış ve iki aylık depolama süresince örneklerin kaplama kısmında ve dolgu kısmında rutin olarak serbest yağ asitliği ve peroksit sayısı ölçümleri yapılmıştır. Ayrıca NMR ile katı yağ indeksi değerleri, kullanılan çikolatalar ve kaplama tabakası için belirlenmiştir. Örnekler depolama süresi sonunda, tanımlayıcı analiz yöntemi ile ve referans örnekler kullanılmak suretiyle duyusal olarak değerlendirilmişlerdir. Çalışmanın sonuçları istatistiksel yöntemler kullanılarak incelenmiştir. Çalışmanın sonucunda ölçülen serbest yağ asitliği ve peroksit sayısı değerlerinin izin verilen yasal limitler içinde olduğu görülmüştür. Yapılan duyusal analizler, iki aylık serin depolama süresinin cilalama işlemi görmüş bitter ve sütlü çikolatalı drajeler için uygun olmadığını; ancak beyaz çikolatalı drajeler için uygun olduğunu göstermiştir. Cilalama işlemi görmüş örneklerin cilalama işlemi görmemiş ürünlere göre daha az dayanıklı olduğu da görülmüştür. Bunun nedeninin kullanılan gum arabik olduğu düşünülmektedir.

Chocolate, dragee, shelf-life, rancidity, sensory analyses Panning may be the oldest form of processed confection, dating back over 1.000 years. A simplified definition of panning would be "a continual and controlled gross-up of a centre by the application of chocolate (or other coating) and cold conditioned air on centers inside a revolving vessel (pan) until the desired size and smoothness is achived". In most cases, hazelnuts, almonds and raisins are used as the filling materials. The product which is obtained by panning process is called "dragee". Chocolate coated hazelnut dragees are produced by coating the roasted hazelnuts with layers of molten chocolate. Their shelf-life are affected by various deterioration mechanisms, the major ones being physical changes in the form of fat and sugar bloom, and chemical changes in the coating materials. Fat bloom is recognized as a grayish coating on the surface of chocolate layer. It looks like the bloom on some ripe fruits such as plums and grapes, and when touched lightly with the finger, it has a greasy appearance and is easily removed. Under the microscope, minute fat crystals are visible. The formation of fat bloom is closely related to polymorphism of cocoa butter. There are four essential polymorphic forms of cocoa butter. Öne of the rather unstable form is the y form which has a melting point of 17°C; another form is called the a form with a melting point of 21-24 °C. Third form is ß* and its melting point ranges between 27-29 °C. There is a gradual transition at ordinary temperatures to ß. This last form is the most stable form. Bloom is formed by transition of the lower melting polymorphs to the stable ß form. The technology of good chocolate production depends on ensuring that only the stable form of the cocoa butter ingredient exists in the final product. Another problem which is seen in dragees is sugar bloom formation. Sugar bloom has a grayish appearance and in a mild form resembles fat bloom when touched with the finger, it is not removed and has no greasy feeling. It occurs generally due to storage problems. Rancidity is the another problem and mostly it is observed in nuts which have high fat content. Rancidity can be divided in two groups as oxidative rancidity and xii hydrolitic rancidity. The type of rancidity caused by the action of air, oxidative rancidity, is widespread in foods but hydrolitic rancidity is more in confectionery because of bad flavor. Hydrolitic or "soapy" rancidity can be a most objectionable defect in a confection containing fat. It arises from the introduction of fat-splitting enzymes present in ingredients such as milk products and cocoa. Lipolytic activity can arise from the activity of molds during the preperation or storage of foods. The objective of this study was to investigate the factors influencing the shelf-life of chocolate coated hazelnut dragees processed and stored at different conditions. Roasted hazelnuts were the only filling material, but three different coating materials (namely milk chocolate, dark chocolate and white chocolate) were used. Materials used in the study are shown in Table 1. As it will be seen from Table 1, dragee samples were stored at two different conditions (room conditions nearly 20 °C, 60 RH % and cool conditions: 3 °C and 60 RH %). The samples were followed with periodical analyses until deterioration limits were reached. These analyses included the use of Nuclear Magnetic Resonance (NMR) for determination of solid- fat index (SFI),determination of free fatty acid content (ffa) and peroxide numbers (PV), as well as sensory analyses. The experimental plan and analyses conducted on the samples are summarized in Table 2. Table! Materials used in the study. The results obtained from peroxide value and free fatty acid content determination are given in Table 3. In this table, only the initial and final values are given for the two sets of analyses. It was observed that white chocolate coated, polished and glazed dragees which were stored at room (ambient) conditions had the highest free fatty acid content and peroxide value increases. The lowest free fatty acid content and and peroxide value increases were observed in dark chocolate coated, unpolished and unglazed dragees which were stored in cool conditions. This must be due to the relatively higher tocopherol content of cocoa powder since dark chocolate also had the highest cocoa powder content. Unpolished and unglazed dragees had lower peroxide and free fatty acid contents. This may be due to gum arabic used for polishing purposes, since some Table 2. The Experimental plan and analyses conducted on the samples researchers have previously reported that gum arabic and shellac polishing may be hygroscopic and that increased water uptake accelerates hydrolitic decomposition. SFI were measured by NMR studies on fats extracted from the coating layers, chocolate ingredients and cocoa butter. When SFI values are evaluated, it was seen that cocoa butter had the highest SFI which indicates products firmness and stability. Milk chocolate and white chocolate had lower SFI values due to mixing of two different fat namely milk fat and cocoa butter. Results obtained from NMR studies are shown in Table 4 and in graphical form in Figure 1. Table 3. Experimental results obtained from ffa and PV analyses on coating layers. Table 4. SFI values of chocolates and cocoa butter determined by NMR 80.00 qj 70.00 * E 20.00 10.00 0.00 -O - Dark chocolate fat ¦ White chocolate fat -A- Milk Chocolate fat -X- Cocoa butter Temperatures, C Figure 1. SFI values for cocoa butter and chocolates studied. Sensory evaluation was applied to all dragee samples and descriptive technique was used. Dragee samples were compared to reference samples with respect to different product attributes. The results analysed by using analyses of variances (ANOVA) and the effects of glazing process and storage conditions (cool storage and room conditions) on the dragees were evaluated. The most interesting result which was obtained by sensory analyses is that all glazed dragees except for white chocolate dragees were affected from cool storage with respect to appearance. This adverse effect was not observed in white chocolate dragees. The results of peroxide value and free fatty acid content determinations also, analyzed by using ANOVA. For this purpose 3*2*2 (r = 4) factorial experimental design was used. The pratical results obtained from this study were that white chocolate coated dragees are the most sensitive products for deterioration and dark chocolate dragees are the most stable products. Another result is that cool storage conditions supply good keeping properties with respect to free fatty acid contents and peroxide value. Therefore, it is concluded that white chocolate dragees can be stored in cool storage without significant deterioration