Thesis Type: Doctorate
Institution Of The Thesis: Bursa Uludağ University, ZİRAAT FAKÜLTESİ, GIDA MÜHENDİSLİĞİ, Turkey
Approval Date: 2004
Thesis Language: Turkish
Student: CANAN ECE TAMER
Supervisor: Ömer Utku ÇopurAbstract:
The aim of this study was to improve nutritional value of boza by addition of various fruit and also by addition of fruit aroma, sensory properties of boza were developed. Moreover, by applying pasteurization it's shelf life was increased. According to the results of the preliminary studies, apricot, raspberry, apple and fruit cocktail (tutti frutti) were the most suitable fruits in boza production. Therefore for producing boza with fruit aroma, the aromas of these fruits were used. Optimum temperature and time for pasteurization was determined as 80QC and 25 minutes, when sensory properties (jelling, consistency increasing and taste) were taken into consideration. Total dry matter, water soluble dry matter, total and reducing sugar, total acidity, pH, ethyl alcohol, carbon dioxide, protein, ash and viscosity analysis were done in sugary raw boza, non-pasteurized unmixed boza, non-pasteurized bozas with fruit and fruit aroma, and as well in all pasteurized samples at the 0th, 7,h.15th, 30th, 45th, 60th, 90th days following pasteurization. Throughout the 90 days of storage, the value of total dry matter in pasteurized unmixed and fruit aroma added bozas was found between 21.19 - 21.64 g/100g. However, in pasteurized unmixed and fruit added bozas the total dry matter value was changed between 20.80 - 25.05 g/100g. Among the fruit added bozas, especially the samples produced by adding fruit cocktail (tutti frutti) have higher total dry matter value than the other samples. Owing to the application, application x time interaction as a statistical mean there was no considerable difference between the total acidity values of pasteurized unmixed, and pasteurized fruit aroma added bozas. For all of the samples of these groups, total acidity (lactic acid base) till 30th days following pasteurization was found as 0.20 g/100g, on the other hand, at the 30th day this value was increased to 0.21 g/100g, but after that day an increase on total acidity was not observed. Total acidity of pasteurized unmixed and fruit added bozas was found between the values of 0.200 - 0.347 g/100g. It was considered that the slight increase in the total acidity during the three months of storage period was derived from the organic acids; passing from fruits to boza. Through the pasteurized unmixed and fruit aroma added bozas, the highest pH value (3.957) was examined in pasteurized unmixed boza at the 0th day, following pasteurization. Whereas, the lowest pH value (3.857) was observed in apricot aroma added boza at the 90th day, following pasteurization. In pasteurized unmixed and fruit added bozas, the highest pH value (4.007) was examined in fruit cocktail added boza at the 0th day, following pasteurization; however, at the 90th day, following pasteurization boza produced with raspberry had the lowest pH value (3.603).IV While the storage period, the carbon dioxide value of pasteurized unmixed and fruit aroma added bozas was changed between 0.153 - 0.263 g/100g. That value for pasteurized unmixed and fruit added bozas was changed between 0.160 - 0.303 g/100g. Ethyl alcohol contents of pasteurized unmixed, fruit aroma, and fruit added bozas was slightly increased during the storage period. The samples of bozas have been storing more than one and half years after the term of analysis. By the way, in none of these samples, as a result of activity of microorganisms souring, swelling and gas exhaustion was not observed. That shows the coherence of applied pasteurization norms. Viscosity of pasteurized unmixed and fruit aroma added bozas was decreased evidently, while the time period after pasteurization increases. In unmixed boza viscosity was observed as 13.40 - 9.80 Pa. s at the date of 0th and 90th following pasteurization respectively. In addition, in apricot aroma added, raspberry aroma added, apple aroma added, and tutti frutti aroma added bozas the viscosity value was found at the date of 0th and 90th following pasteurization as 12.77 - 9.67 Pa.s, 12.67 - 9.93 Pa.s, 12.93 - 9.97 Pa.s, and 12.67 - 9.77 Pa.s respectively. The same situation was observed in the bozas produced with fruits. At the 0th day following pasteurization, among the samples the lowest viscosity was measured as (11.87 Pa.s) by using boza produced with raspberry. However, boza produced with tutti frutti had the highest viscosity (30.00 Pa.s) markedly. At the 90th day following pasteurization, again the boza produced with raspberry had the lowest viscosity 8.57 Pa.s, and boza produced with tutti frutti had the highest viscosity 16.57 Pa.s. Especially, after the 15th day following pasteurization, decrease in the viscosity value related to the separation of serum was found to be attractive. After the storage period, the volume of the serum that was separated from boza was gradually increased, since when the jars were shaken bozas obtained the former appearances, after that no further separation of serum was observed. This application shows that the problem of separation of serum, occurred during the protection of boza by pasteurization, can be passed over. When the results of sensory analysis were evaluated it was concluded that although unmixed boza was preferred by some panelists, boza produced with fruit and fruit aroma were liked and can be consumed.