Changes in composition of wet tarhana during production and in different storage conditions

ABSTRACT CHANGES IN COMPOSITION OF WET TARHANA DURING PRODUCTION AND IN DD7FERENT STORAGE CONDITIONS Mustafa ERBAŞ Ph. D. in Food Engineering Adviser: Prof. Dr. Muharrem CERTEL June 2003, 160 pages In the present study, the effects of fermentation time, different storage type and storage period on microbiological, chemical, physical and sensory properties of wet tarhana, which is a Turkish traditional and cultural product, were researched. For this goal, changes in some important properties of tarhana during fermentation time (0, 1., 2., and 3. days), storage period (1., 2., 3., 4., 5. and 6. months) and effects of different storage type (wet tarhana at room temperature without using any preservative, with 1000 mg/kg sodium benzoate, 6.5% salt, wet tarhana at refrigerator (+ 4 °C) and dried tarhana (control) at room temperature) were searched. To evaluate the microbiological quality of tarhanas, total mesophilic aerobic bacteria (TMAB), lactic acid bacteria (Lactobacillus ssp.), coliform bacteria and yeast- mould were enumerated. Physical and chemical properties of the tarhanas were determined by analyzing dry matter, titratable acidity, pH, total nitrogenous compound, total ether extract, cellulose, salt, ash, minerals composition, energy content, water activity, thiobarbutiric acid number (TBA), ethyl alcohol, sugars (glucose, lactose, galactose, maltose and sucrose), free amino acids and carbonyl compounds (acetaldehyde, diacetyl and malon aldehyde). Furthermore, sensorial properties (color, flavor, taste, consistency and homogeneity) and rheological properties of the tarhana soup were determined. During fermentation time, the number of TMAB, lactic acid bacteria and yeast- mould were decreased from 106 to 103, and coliform bacteria were not found. Dry matter (from 40.22% to 38.32%) and pH (from 4.61 to 4.05) of the tarhana were decreased. However, acidity (from 2.65 % to 4.15 %), ethyl alcohol (from 395 mg/kg to 954 mg/kg) and total free amino acids (from 9993 mg/kg to 15358 mg/kg) of the tarhana were increased. Total nitrogenous compounds (16.79%), total ether extract (3.92%), cellulose amount (2.76%) of the tarhana were not changed. The highest microorganism count was founded in the tarhana stored at refrigerator, whereas the lowest counts were founded in dried and salty tarhanas. Physical, chemical and sensorial properties of the salty tarhana and the tarhana stored at refrigerator were better preserved than the others, while those properties of the dried tarhana were the worst. Especially, sensorial and aromatic properties of the dried tarhana was significantly worse than the wet tarhanas The dried tarhana was lost 69 % of their acetaldehyde content compared to the that of wet fresh tarhana. mThe number of microorganisms in the tarhanas continuously decreased during storage period. Some parameters (acidity, pH, sugars, free amino acids etc.) of the wet tarhanas changed depending on partially going on fermentation during storage, while nutritional and aromatic properties of the dried tarhana partially lost. Water activities of the wet tarhanas were about 0.95-0.97, while water activity of the dried tarhana was 0.63. The tarhana soup acted as pseudoplastic, its flow and consistency index were calculated as 0.39 and 1.95 (pas") respectively. It was found that the tarhana contains important macro and micro minerals, essential for human diet. Energy content of the tarhana was calculated as 372.3 kcal/100g (d.b.). In conclusion, nutritional and aromatic profile of the tarhana developed during fermentation process. However, drying process caused nutritional and aromatic loss in tarhana. Also, microbiological, chemical, physical and sensorial properties of the wet tarhana were better than the dried tarhana. In case of wet tarhana is produced hygienically and packed hermetically, it can be stored and marketed acceptably for 6 mounts at refrigerator without using any preservative or at room temperature with 6.5 % (w.b.) salt. ANAHTAR KELİMELER: Wet tarhana, fermented cereal product, storage, sugar, free amino acids COMMITTEE: Prof. Dr. Muharrem CERTEL (Adviser) Prof. Dr. Hasan YAYGIN Prof. Dr. Recai ERCAN Assoc. Prof. Dr. Feramuz ÖZDEMİR Assoc. Prof. Dr. Hüseyin BASIM IV