Farklı orijinli kakao kitlelerinin bitter çikolata kalitesi üzerindeki etkisi
Effects of different geographical originated cocoa masses on dark chocolate quality
Yazar: ÖZNUR KARĞI
Danışman: YRD. DOÇ. DR. FATMA EBRU FIRATLIGİL DURMUŞ
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:
Kakao (Theobroma cacao), genellikle Güney Amerika ve ve Fildişi Sahilleri gibi tropikal iklim bölgelerinde yetişen, yüksek ekonomik değere sahip olan bir tarım ürünüdür. Kakao çekirdeğinden, çikolatanın çeşidine göre farklılık gösteren temel hammaddelerini oluşturan kakao tozu, kakao kitlesi, kakao yağı ve ayrıca nib üretimi yapılabilmektedir. Dünyada yaygın olarak kullanılan üç farklı kakao çeşidi vardır. Bunlar daha çok Ekvator, Venezuela ve Batı Afrika'da yetişmekte olan Criollo, Forastero ve ikisinin hibriti olan Trinitario türleridir. Diğer türlere göre daha kaliteli olan çekirdek türü Criollo iken, dünyadaki üretimin yaklaşık %95'lik kısmını oluşturan tür ise Forastero'dur. Orijin ülkelerde fermentasyon ve kurutma proselerinden geçen taze kakao çekirdekleri, yerel varyasyonlar ve geleneksel proseslere göre farklı işlem görebilmektedirler. Bu sebeple, fermente kakao çekirdeğinin kompozisyon profili, kakao ürünlerinin tat ve aromasını etkileyen en büyük faktör olup tam anlamıyla kakao çeşidi ve coğrafi orijinine bağlıdır. Orijine bağlı olarak değişen kakao çekirdeğinin aromatik kalitesi, hasat sonrası uygulamaya(fermentasyon, kurutma ve depolama) ve endüstriyel proses boyunca kullanılan parametrelere de bağlıdır. Toprağın çeşidi, iklim, tarım alanı ve kabuk olgunluk derecesi de aromatik profili etkilemektedir. Farklı coğrafi orijinlere sahip kakao çekirdekleri farklı organoleptik özelliklere sahiptir ve bunun da çikolatanın kalitesini etkilediği duyusal analizlerle test edilmiştir.
Tüketiciler tarafından sıkça tercih edilen şekerleme ürünlerinden biri kakao ürünü olan çikolatadır. Çikolata, içerdiği bileşene bağlı olarak sütlü, bitter ve beyaz olarak üç çeşide ayrılmaktadır. Daha çok zevk için tüketilen çikolata, sakinleştirici, gevşetici ve potansiyel bir antidepresan olma özelliğine de sahiptir. Çikolata sadece haz verdiği için değil, aynı zamanda antioksidan içeriği yüksek olması nedeniyle sağlık yararları için de tüketilmektedir. Son zamanlarda yapılan pek çok çalışmada, bitter çikolata tüketimi ile, içeriğinde bulunan polifenoller sayesinde LDL(düşük yoğunluklu lipoprotein) kolesterol oksidayonunun engellenerek kalp rahatsızlıklarının önlendiği görülmüştür. Ayrıca, sınırlı miktarda bitter çikolata tüketmenin kardiyovasküler sorunları azaltarak, kan basıncı ve kolesterol seviyesini düzenleyip, kansere karşı etkili olabileceği sonuçları, yapılan çalışmalarla elde edilmiştir.
Bu çalışmada, farklı coğrafi orijine sahip kakao kitlelerinin bitter çikolatanın kalitesini nasıl etkilediği araştırılmıştır. Bu amaçla Kolombiya, Venezuela, Madagaskar, Ekvator ve Tanzanya olmak üzere beş farklı orijinli kakao kitlesi ile pilot ekipmanlar kullanılarak bitter çikolata üretimi gerçekleştirilmiştir. Hazırlanan numuneler, tanımlayıcı analiz metodu uygulanarak duyusal olarak değerlendirilmiş ve reolojik analiz, nem analizi, su aktivitesi analizi, pH analizi, toplam yağ analizi ve renk(parlaklık) analizi yapılmıştır.
Çalışma sonucunda, farklı coğrafi orijinlere sahip kakao kitleleri ile üretilen bitter çikolataların organoleptik özelliklerinin birbirinden farklı olduğu, bunun yanı sıra orijine bağlı olarak numunelerin reolojik değerleri, nem ve su aktivite değerleri, pH ve toplam yağ miktarları ve renkleri farklılık göstermektedir.
Farklı coğrafi orijinli kakao kitleli bitter çikolataların viskozite değerleri birbirinden farklı olup, Kolombiya ve Ekvator orijinli bitter çikolatalar en yüksek viskoziteye sahipken, Madagaskar orijinli bitter çikolata en düşük viskoziteye sahiptir. En yüksek akma gerilimine sahip numune Venezuela orijinli ve ardından Ekvator orijinli bitter çikolatayken, bu iki numuneye kıyasla oldukça düşük akma gerilimine sahip numune Tanzanya orijinli bitter çikolatadır.
Kakao kitlesinin orijini, nem ve su aktivitesi değerlerinde de farklılığa neden olmaktadır. En yüksek değerlere sahip numune Venezuela orijinli çikolata iken Madagaskar orijinli çikolata en düşük nem ve su aktivitesi değerine sahiptir.
Farklı orijinli kakao kitleleli bitter çikolataların pH değerlerinin birbirine yakın olduğu gözlenmiştir. Çikolata numuneleri arasında diğerlerine göre en düşük pH değerine sahip olan numune Madagaskar orijinli bitter çikolatadır.
Kakao kitlesinin coğrafi orijinin, bitter çikolataların toplam yağ değerlerinin farklı olmasında etkili olduğu görülmektedir. Tanzanya orijinli bitter çikolatanın içerdiği toplam yağ en yüksek olmak üzere, Ekvator ve Madagaskar orijinli bitter çikolataların yağ değerleri birbirine çok yakındır. Kolombiya orijinli bitter çikolata ise en düşük yağ oranına sahiptir.
Farklı coğrafi orijine sahip kakao kitlelerinden elde edilen numunelerin renkleri de birbirinden farklı bulunmuştur. En yüksek parlaklığa sahip olan numune Madagaskar orijinli bitter çikolata numunesidir. Tanzanya orijinli bitter çikolatanın L-parlaklık değeri diğerlerine göre daha düşük bulunmuştur.

Abstract:
Cocoa (Theobroma cacao) is an agricultural product that grows in tropical climates, such as South America and Côte d'Ivoire. Cocoa powder, cocoa mass, cocoa butter and also nib can be produced from the cocoa beans, which are the main raw materials that differ according to the type of chocolate. There are three different types of cocoa that are widely used in the world. These are mostly Criollo, Forastero and Trinitario species, both of which are grown in Ecuador, Venezuela and West Africa. The bean type, which is of higher quality than other species, is Criollo, while the species constituting about 95% of the world production is Forastero. Fresh cocoa beans, which pass through fermentation and drying plants in the original countries, can be treated differently according to local variations and traditional processes. For this reason, the composition profile of the fermented cocoa bean is the biggest factor that affects the taste and aroma of cocoa products and depends on the cocoa variety and its geographical origin.
The aromatic quality of the cocoa bean due to its origin also depends on the post-harvest application (fermentation, drying and storage) and the parameters used during the endogenous transformation. The type of soil, climate, agricultural area and the degree of shell maturity affect the aromatic profile. Cocoa beans with different geographical origins have different organoleptic properties and this has been tested by sensory analysis that affects the quality of chocolate.
One of the most frequently preferred confectionery products by consumers is chocolate, a cocoa product. Chocolate, milk, dark and white depending on the component is divided into three varieties. The chocolate consumed for more pleasure has the property of being a calming, relaxing and potential antidepressant. Chocolate is consumed not only for its pleasure, but also for its health benefits due to its high content of antioxidants. In many recent studies, with the consumption of bitter chocolate, it has been observed that by preventing the oxidation of LDL (low density lipoprotein) cholesterol thanks to the polyphenol in its content, heart diseases are prevented. In addition, the reduction of cardiovascular problems by consuming a limited amount of dark chocolate, blood pressure and cholesterol levels can be effective against cancer, the results have been obtained by studies.
In this study, it was investigated how the cocoa mass of different geographical origin affect the quality of dark chocolate. For this purpose, dark chocolates were produced
by using cocoa mass with five different origins from Colombia, Venezuela, Madagascar, Ecuador and Tanzania. The prepared samples were evaluated sensitively by using descriptive analysis method and moisture analysis, water activity analysis pH analysis, total fat analysis, color (brightness) analysis and rheological analysis were performed.
For preparing the samples, each cocoa mass type(Ecuador, Venezuela, Madagascar, Kolombiya and Tanzania originated cocoa masses) is processed with cocoa butter, sugar and emulsifier(lecithin) seperately. Firstly, cocoa mass and sugar mixed and refined. After refining, in the conching process cocoa butter and emulsifier are added. After conching process, the chocolate samples are tempered and moulded. The moulded chocolate samples are passed from the cooling tunnel and demoulded. The chocolate samples are analyzed both as solid and liquid.
For sensory analyzing of different originated solid dark chocolates, descriptive analysis is used with 9-point hedonic scale. Nine core flavour attributes are considered in initial training cocoa, acid, astringent, bitter, fruity, floral, nutty, woody and spicy flavours. It is scored the intensity of the flavour attributes for each flavour descriptor using 9-point scales with a possible range of scores from 0 to 9 where the higher numbers denoted stronger flavour intensities. 
For measuring plastic viscosity and yield value according to Casson Model, the liquid chocolate samples are analyzed by VT550 viscosimeter at 40°C. The moisture content of the melted at 40°C and homogenously mixed chocolates are measured by V20 Volumetric KF Titrator with Karl Fischer method. For measuring the water activity of the chocolates, all chocolates are melted at 40°C and after homogenously mixing, it is measured at the room temperature by Pawkit water activity equipment. pH value of the chocolates are measured by FG2 FiveGo pHmeter with 10%  solution of warm water. The melted and homogenized chocolate samples are analyzed with Color Flex EZ colormeter at room temperature for meauring lightness. The total fat content of the samples are mesured with Soxhelet method. The data obtained from the analyzes are determined by using Windows based SPSS 20.0 (SPSS Inc., Chicago, Illinois, US) statistical package program. p <0.05).
As a result of the study, the organoleptic properties of the dark chocolate produced by cocoa mass with different geographical origins are quite different from each other, as well as the rheological values of products, moisture and water activity values, pH and total fat quantities and colors depending on the origin. 
The viscosity values of bitter chocolates of origin cocoa mass differ from each other, while bitter chocolates of Colombian and Equator origin have the highest viscosity,  the dark chocolate of Madagascar origin has the lowest viscosity. While the sample with the highest yield stress is dark chocolate of Venezuelan origin and then of Equatorial origin, the sample with very low yield stress is Tanzanian origin dark chocolate compared to these two samples.
The origin of the cocoa mass also causes differences in moisture and water activity values. The sample with the highest values is the chocolate of Venezuela origin and the chocolate of Madagascar origin has the lowest moisture and water activity value.
It was observed that the pH values of dark chocolate with origin cocoa mass were close to each other. Among the chocolate samples, the sample with the lowest pH value is the bitter chocolate of Madagascar origin.
It is seen that the cocoa masses of origin are effective in the different fat values of dark chocolate. The total fat content of Tanzanian origin dark chocolate is the highest, whereas the fat values of Ecuador and Madagascar origin dark chocolate are very close to each other. Dark chocolate of Colombian origin has the lowest fat content.
The colors of the samples obtained from cocoa masses of different geographical origin were also different from each other. The sample with the highest gloss is a dark chocolate sample of Madagascar origin. L-brigtness value of Tanzanian origin dark chocolate was lower than the others.
In this study, it is seen that the different originated cocoa beans affect the taste of chocolate differently. The chocolate of Colombian origin has a fruity and bitter taste, and also cocoa intensity is high. The chocolate of Venezuelan origin has mild chocolate taste, slightly bitter and distinct fruity notes like plum and cherry. The chocolate of Madagascar origin has a winey, putrid and citrus taste. The chocolate of Ecuador origin has a balanced taste profile with feeling low chocolate taste and supported by floral, fruity, grass and earthy notes. The chocolate of Tanzanian originated has a fruity, nutty, sweety and soft taste profile.
It was concluded that the total amount of fat and moisture contained in cocoa beans had a significant effect on the different rheological values of chocolates. The high fat content ensures that the rheological values of the chocolate are low, while the high moisture and water activity content is particularly effective in increasing the yield stress. The rheological values decrease with increasing fat content of chocolate. Moisture and water activity are important in terms of rheological properties, shelf life, process and storage conditions of chocolate depending on the cocoa bean variety. The pH value of chocolate is one of the main factors that are based on cocoa and affect the characteristic aroma of chocolate and can be controlled by cocoa producers. It affects color as well as aroma. The color of cocoa powder is an important feature because it is often used because of the aroma it provides to various foods in addition to its coloring. Cocoa powder contains naturally occurring colorants, including flavonoids, and is a measure that can be affected during the alkalization and roasting processes, which are important steps for cocoa producers. Levels and types of chemicals responsible for color formation; The genetic background of cocoa is affected by a complex of factors including climatic and soil conditions and post-harvest processes.
A good fermentation is important for the oxidation and condensation reactions that lead to the formation of tannin compounds that give the cocoa bean its characteristic brown color. Fermentation should be stopped at the right time, otherwise very fermented very dark cocoa beans are formed. The color of chocolate depends on the pH of the cocoa bean, the formation of tannin components and the proper drying and fermentation conditions, and may vary depending on the origin of the cocoa bean.