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Microbial Biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
Fruits, vegetables, meat, poultry, seafood, dairy products, and various food products differ in their biochemical composition and are therefore subject to spoilage by different microbial populations. Such changes depend upon the nature of the microbes involved in the spoilage. Thus, degradation of apple juice by yeast gives an alcoholic taste to the juice. Yeasts convert the carbohydrate into ethanol. Bacteria that attack food proteins convert these into amino acids, which are broken down again into foul-smelling end products. Digestion of cysteine, for example, yields hydrogen sulfide, giving a rotten egg smell to food. Digestion of tryptophan yields indole and skatole, which give food a fecal odor. Two other products of the microbial metabolism of carbohydrates are (i) acid that causes foods to become sour and (ii) gases that cause sealed cans to swell. Digestion of fats, as in spoiled butter, yields fatty acids, giving a rancid odor or taste to food. Food may become slimy because of the production of capsules in bacteria. There may be pigment development, giving an odd color to foods.
Microbial biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Fruits, vegetables, meat, poultry, seafood, dairy products, and various food products differ in their biochemical composition and are therefore subject to spoilage by different microbial populations. Such changes depend upon the nature of the microbes involved in the spoilage. Thus, degradation of apple juice by yeast gives an alcoholic taste to the juice. Yeasts convert the carbohydrate into ethanol. Bacteria that attack food proteins convert these into amino acids, which are broken down again into foul-smelling end products. Digestion of cystein, for example, yields hydrogen sulfide, giving a rotten egg smell to food. Digestion of tryptophan yields indole and skatole, which give food a fecal odor. Two other products of the microbial metabolism of carbohydrates are (1) acid that causes foods to become sour and (2) gases that cause sealed cans to swell. Digestion of fats, as in spoiled butter, yields fatty acids, giving a rancid odor or taste to food. Food may become slimy due to production of capsules in bacteria. There may be pigment development, giving an odd color to foods.
Industrial Odor Control
Published in Paul N. Cheremisinoff, Air Pollution Control and Design for Industry, 2018
Odor modification (especially in the sense of counteraction) has also been rationalized as a means by which a malodor is incorporated into an overall odor mixture that is pleasant and/or mild. For example, sewage odor is considered to be caused to a major degree by indole and skatole. The same compounds are components of oil of jasmine. By adding an odorant that has the floral attributes of jasmine but is lacking the indole component to an appropriate sample of sewage odor, the malodor is said to disappear into the floral note to a considerable degree. The resulting odor is said to be no longer unpleasant and less intense. However, these claims have not been checked by independent investigators, as the compositions of odor modifiers remain proprietary information with the companies that sell them.
Improved water quality and reduction of odorous compounds in anaerobic lagoon columns receiving pre-treated pig wastewater
Published in Environmental Technology, 2018
Ariel A. Szogi, John H. Loughrin, Matias B. Vanotti
Results on water-quality changes and odorous compound concentration of our column study showed that both SS and SS + NDN pre-treatments significantly reduced malodor concentrations in lagoon liquid with respect to the conventional lagoon storage used as a control treatment. However, the SS and SS + NDN pre-treatments differed in their efficiencies to reduce inflow concentrations of phenol, p-cresol, 4-ethylphenol, indole, and skatole. These differences in efficiencies were confirmed by the correlation of SOC to odor panel analysis tests results and water-quality parameters concentrations (NH4-N and COD) in liquid sampled from the columns. The odor panel analysis revealed that differences between the control and the SS pre-treatment on both odor intensity and hedonic tone means were not statistically significant, indicating that the SS pre-treatment was inefficient to significantly reduce the human sense of malodor. The SS + NDN pre-treatment had the greatest improvements in reducing by about 99% the concentrations of all selected compounds in liquid stored in the lagoon that resulted with the lowest odor intensity and hedonic tone. These results support the use of pre-treatment technologies such as SS + NDN to simultaneously reduce malodor compound concentrations and nutrients such as NH4-N from liquid stored in lagoon structures. Ultimately, the SS + NDN pre-treatment would eliminate associated ammonia and malodor emissions during both storage and land application of lagoon liquid.
Review of the effects of wastewater biosolids stabilization processes on odor emissions
Published in Critical Reviews in Environmental Science and Technology, 2019
Ruth M. Fisher, Juan Pablo Alvarez-Gaitan, Richard M. Stuetz
Organic volatile aromatic compounds (OVACs) such as toluene, styrene, p-cresol, indole, ethylbenzene, and skatole were detected in biosolids headspaces from about day 30 of storage (Chen et al., 2006). This delay may be due to substrate competition with VSC precursors, the slower degradation of OVAC precursors, or the gradual conversion of compounds over time (Chen et al., 2006; Kacker et al., 2011). Concentrations of OVACs in the headspace were lower than the peak VSC emissions by approximately two orders of magnitude. However, due to their low odor thresholds, OVACs may still contribute to biosolids odors (Johnston, Higgins, Brandt, Toffey, & Eschborn, 2009).
Factors affecting the adsorption of gaseous environmental odors by activated carbon: A critical review
Published in Critical Reviews in Environmental Science and Technology, 2018
Nhat Le-Minh, Eric C. Sivret, Ari Shammay, Richard M. Stuetz
Indole, skatole and pyridines are heterocyclic N-containing compounds that are common environmental odorants. It is well known in the air quality control industry that activated carbon has excellent adsorptive capacity for these compounds (El-Guendi, 1991); however no studies on removal mechanisms were found in the surveyed literature.