Biochemical Oxygen Demand
The purpose of this exercise is to investigate the relationship of water quality and the consumption of oxygen by aerobic bacteria. Biological Oxygen Demand (BOD) is a measure of how polluted a particular aquatic system is with nutrients which increase the activity of aerobic bacteria. Researchers measure BOD as an index of water pollution or general water quality in streams, rivers, and lakes.
Biochemical Oxygen Demand is a common, environmental procedure for determining the extent to which oxygen within a sample can support microbial life. The following tutorial explores the theory and basics of performing this test when one has little or no prior experience. This method is popular in many environmental laboratories analyzing waste water, compost, sludge, and soil samples. Although methods for each matrix are similar, this tutorial focuses on the method associated with only waste water effluents.
The test for Biochemical Oxygen Demand is especially important in waste water treatment, food manufacturing, and filtration facilities where the concentration of oxygen is crucial to the overall process and end products. High concentrations of dissolved oxygen (DO) predict that oxygen uptake by microorganisms is low along with the required break down of nutrient sources in the medium (sample). On the other hand, low DO readings signify high oxygen demand from microorganisms, and can lead to possible sources of contamination depending on the process.
Performing the test for Biochemical Oxygen Demand requires a significant time commitment for preparation and analysis. The entire process requires five days, and it is not until the last day where data is collected and evaluated. During this time, samples are initially seeded with microorganisms and supplied with a carbon nutrient source of glucose-glutamic acid. The sample is then introduced to an environment suitable for bacterial growth at reproducible temperatures, nutrient sources, and light within a 20 degree Celsius incubator such that oxygen will be consumed. Quality controls, standards and dilutions are also run to test for accuracy and precision. Determination of the dissolved oxygen within the sample can be determined through Winkler titration methods. The difference in initial DO readings (prior to incubation) and final DO readings (after 5 days of incubation) predicts the BOD of the sample. A suitable detection limit as per environmental QC is 1 mg/L.
To practice slow and fast process of vinegar, to measure some parameters of the vinegar.
Vinegar is a fermented solution that contains acetic acid. Vinegars contain some other acids like citric acid, tartaric acid besides acetic acid. Vinegar products don’t have a time limitation for shelf-life due to it’s stability. Vinegar is basically used as a flavor. Because of it’s acetic acid content (4-6 %), it preserves the foods. Also, it is a color stabilizer and cleaning agent.
To search and practise usage of whey in different areas.
Whey is a mixture of water and organic compounds gained from cheese. 90 kg of 100 kg milk operated as cheese consist of whey. 360.000 tone whey is obtained in our country. It is a huge waste because of dry matter and rich organic content of whey beside its amount. Before separation or performing waste treatment, leaving whey to nature causes a big organic pollution.
Waste treatment is operable but, it is pretty much expensive because of high fat and acid content of whey. Curd cheese, lactose, albumin and dry whey can be gained by separation. These materials have different areas in industry to be used. Lactose obtained by crystallized can be used in confectionary industry, chemical and medical areas. Whey has 1,5 % dry matter. This dry matter can be gained as curd cheese by boiling of whey. But, there is stil dry matter in whey at ratio 5.5-6.5 %. This dry matter is gained as dried whey by removing the water. Dried whey (whey powder) can be used as a filling material in ice cream, yogurt etc. It can be added in bakery products to improve taste and color. It can be used as animal feed
To practice making white cheese.
Cheese is a fermented milk product. Milk protein=casein is coagulated by rennet and milk sugar=lactose is fermented by cheese culture. Then whey is seperated and solid part=cheese is obtained. There are many types of cheese according to properties of milk, production technique, ripening technique and variety of starter culture.
Properties of milk are important. Generally in raw milk:
1. Amount of protein (especially amount of casein) should be at a high level.
2. Fat and dry matter ratios should be at normal levels.
3. Total microorganism burden should be lowly.
4. There shouldn’t be any kind of inhibitor material like antibiotic, disinfectant etc.
5. Coagulation test with enzyme should be positive.
Procedure techniques are changable with regard to type of cheese. There are several coagulation; acid coagulation, heat coagulation, enzyme coagulation, crystallization, concentration or combination of two coagulation type.
To familiarize students with the basic procedures of successful wine making and to measure several parameters that changes during the fermentations.
Wine is an alcoholic beverage fermented from fruits, especially from red or white grapes. Wine has a history dating 6000 BC originated Georgia and Iran. Wine is made from varieties of Vitis vinifera. Most known varieties are: Riesling, Chardonnay, Cabernet Sauvignon, Pinot Noir, Gewurztraminer, Sauvignon Blanc and Muscat. A characteristic wine is obtained with each variety.
Saccaharomyces cerevisiae is known as wine yeast. Different strains of yeasts can be used also in wine producing. Yeasts ferment sugar found in the grapes and form alcohol (ethyl alcohol) and CO2 as main compounds. By the way, yeasts produce second metabolites: higher alcohols, esters, organic acids, and carbonyl compounds. These effect wine quality in positive way.
There are many factors particularly ‘terroir’ effecting wine characteristic. Terroir is a concept comprising the varieties of grapes used, elevation and shape of the vineyard, type and chemistry of soil, climate and seasonal conditions and the local yeast cultures. Terroir has also a great effect on fermentation and aging processes.
Generally wine is classified according to place of origin or appellation (Bordeaux, Mosel etc.), vintage or varietal (Chardonnay, Cabernet Suvignon etc.) and vinification methods (sweetness, fortied, color etc.).
A general production of wine: