ABSTRACT
BACKGROUND: Pyrazines are used in food industry to impart the foods nutty-roasted flavor. However, their extraction from natural sources is difficult and expensive. At the same time, there is awareness against the chemical food additives. Microorganisms are approved as natural producers of flavors. The aim of the present study was to assess the ability of the newly isolated fungus Tolypocladium inflatum SRH81 to produce pyrazines and studying the effect of encapsulation in gum Arabic on the quality of the biogenerated volatiles. The parameters affecting the biogeneration of pyrazines were optimized. The headspace volatiles of each culture were isolated and identified by solid phase microextraction (HS-SPME) and gas chromatography coupled with mass spectrometry (GC-MS). The volatiles showed the highest pyrazines content and best nutty-roasty flavor was subjected to encapsulation. RESULTS: The selected fungus was identified as Tolypocladium inflatum SRH81. A high correlation was found between the consumed sugar and dry matter content of each culture. Incubation of the fungus culture enriched with 0.5 g amino acids/50 mL medium for 12 days at pH 8 showed the highest generation of pyrazines and best odor sensory quality. Nine pyrazines were identified among them 2-methylpyrazine was the major compound after incubation for 12 days. A positive correlation was found between the total pyrazines and intensity of roasty-nutty aroma. Encapsulation gave rise to a significant decrease in the total volatiles, while the odor intensity showed insignificant decrease. CONCLUSIONS: The results of the present study revealed the potential ability of Tolypocladium inflatum SRH81, that was isolated from Egyptian soil, to produce pyrazines having roasted- nutty aroma.
ABSTRACT
Background Sugarcane bagasse was shown to be an adequate substrate for the growth and aroma production by Trichoderma species. In the present work the ability of Trichoderma viride EMCC-107 to produce high yield of coconut aroma in solid state fermentation (SSF) by using sugarcane bagasse as solid substrate was evaluated. The produced aroma was characterized. Results Total carbohydrates comprised the highest content (43.9% w/w) compared with the other constituents in sugarcane bagasse. The sensory and gas chromatography-mass spectrometric (GC-MS) analysis revealed that the highest odor intensity and maximum yield of volatiles were perceived at the 5th d of induction period. The unsaturated lactone, 6-pentyl-α-pyrone (6-PP), was the major identified volatile compound. Saturated lactones, δ-octalactone, γ-nonalactone, γ-undecalactone, γ-dodecalactone and δ-dodecalactone, were also identified in the coconut aroma produced during the induction period (12 d). A quite correlation was found between the composition and odor profile of the produced aroma. The effect of varying the concentration of sugarcane bagasse on 6-PP production and biomass growth was evaluated. The results revealed high 6-PP production at 4.5 g sugarcane bagasse whereas the biomass showed significant (P < 0.05) increase by increasing the concentration of sugarcane bagasse. Conclusion The concentration of 6-PP, the most contribution of coconut aroma, produced in present study (3.62 mg/g DM) was higher than that reported in previous studies conducted under the same fermentation conditions. The significant increase in biomass with increasing the concentration of sugarcane bagasse may be attributed to the increase in sugar content that acts as carbon and energy source.
