Volatile compounds in whole meal bread crust: The effects of yeast level and fermentation temperature.
The influence of fermentation temperatures (8°C, 16°C, and 32°C) and yeast levels (2%, 4%, and 6% of the flour) on the formation of volatile compounds in the crust of whole meal wheat bread was investigated. The fermentation times were regulated to optimum bread height for each treatment. The volatile compounds were extracted by dynamic headspace extraction and analyzed by gas chromatography-mass spectrometry. The results were evaluated using multivariate data analysis and ANOVA. In all crust samples 28 volatile compounds out of 58 compounds were identified and the other 30 compounds were tentatively identified. Higher fermentation temperatures promoted the formation of Maillard reaction products 3-methyl-1-butanol, pyrazine, 2-ethylpyrazine, 2-ethyl-3-methylpyrazine, 2-vinylpyrazine, 3-hydroxy-2-butanone, 3-(methylsulfanyl)-propanal, and 5-methyl-2-furancarboxaldehyde whereas at lower temperature (8°C) the formation of 2- and 3-methylbutanal was favored. Higher levels of yeast promoted the formation of 3-methyl-1-butanol, 2-methyl-1-propanol and 3-(methylsulfanyl)-propanal, whereas hexanal was promoted in the crust fermented with lower yeast level.
Enhanced probiotic viability and aromatic profile of yogurts produced using wheat bran (Triticum aestivum) as cell immobilization carrier
Abstract The effect of wheat bran ( Triticum aestivum ) as a cell immobilization carrier for probiotic yogurt production on cell viability, composition of volatile compounds and sensory characteristics, was studied. Wheat bran was delignified and separately used as a carrier for the immobilization of Lactobacillus casei ATCC393 and Lactobacillus bulgaricus DSM20081. Both biocatalysts were freeze-dried without the addition of cryoprotectants and were used for yogurt fermentation at 40 °C. Their operational stability was evaluated during successive yogurt fermentation batches until they were inactivated. The yogurts fermented using the immobilized biocatalysts were compared with those fermented with free Lactobacillus cells and with conventional yogurt culture ( Streptococcus thermophilus and L. bulgaricus ). The novel yogurts showed significantly higher cell viabilities during storage at 4 °C. In addition, the immobilized biocatalysts showed higher survival rates during exposure to simulated gastric juice (pH 3.0). The immobilized biocatalysts significantly affected the production of volatile compounds, indicating, in combination with the sensory evaluations, potential for good-quality probiotic yogurt production by freeze-dried ready-to-use immobilized starters.
Mite population density analysis of stored dried apricots in Turkey
The aim of this study was to determine the population density of mite species attacking stored dried apricots in Malatya, Elazig and Izmir regions of Turkey. Storage construction types and duration of storage were also considered. The samples were collected during 2000–2003 in the most important apricot producing areas (Malatya and Elazig) and the exporting center (Izmir). Frequency of occurrence and rates of intensity of infestations were determined (16.50% from Malatya, 3.19% from Elazig and 80.49% from Izmir). A total of 16 mite species belonging to 13 genera and 11 families were identified during the surveys. The pest species Carpoglyphus lactis (L.) (Astigmata: Carpoglyphidae) was the most abundant species recorded (69.14% of samples). The highest infestation value recorded was 15,534 mites per kg.