Problem and its importance: Starter is the "heart" of the cheese making industry. only by proper handling of starter can good quality cheese be made. The economic loss from contaminated starter may prove disastrous to a cheese plant if proper corrective measures are not taken. Milk usually contains a variety of bacteria. Under plant conditions some of these bacteria get into the mother starter or bulk starter unless extreme caution is used. Comparatively little is known about how one organism influences another when grown in milk. This problem is important in the cheese industry. Purpose: The purpose of this research project is to determin the effect of some common contaminants on cheese starters. Some of the off flavors and slow acid production found in cheese making may be due to the results of contaminant organisms growing with the starter organisms. If this be true, more information on this subject will prove valuable. Some organisms have detrimental effects on milk. The question arises: What will two different organisms do when grown together in milk? Streptococcus lactis is important in the cheese industry because it satisfactorily produces the acid necessary in cheese making. If some organism inhibits or stimulates this acid production when grown with Streptococcus lactis, it is important that the cheesemaker know this. Scope: Only those contaminants commonly found in dairy products are considered in this project. Simulated plant conditions are used; that is, the starter being tested is contaminated one evening and the results checked and read the next day. Commercial lactic acid cheese starter from the Hansen's Laboratories and milk from the Utah State Agricultural College Creamery are used to propagate the starter. Different percentages of the contaminant are added to the starter to determine the effects of varying numbers of the contaminant on the starter organisms. A control starter is incubated and tested along with the contaminated starter. After the starters have been incubated at 70°F. Overnight, the following tests are run on each one: activity, acidity, pH, creatine, odor and appearance, and microscopic count. Starter vitality may be determined by the above tests; however, these do not indicate how the contaminant organisms affect cheese when carried on into the cheese making process. Therefore, this project is limited to the effects of contaminants on the starter and not on cheese. This latter problem is reserved for future investigators.

In this study, the physico-chemical chances occurring in white cheese and possible effects of starter culture combinations to the ripening period during 30 days storage examinated. A total of thirty six lactic acid bacteria were isolated from a cheese made witohout using starter culture. For identification gram staining, catalase, gas production and coagulation tests were performed. For determination of species API50 CH (BioM&eacute / rieux) and partial 16S rDNA gene sequence analysis were used. Four cheese were produced, one by using commercial starter culture [Lyofast CMS (Lactococcus lactic subs. lactis and Lactococcus lactis subs. cremoris)]as control the other three by using different combinations of isolates [Lactococcus lactic subs. lactis (13%) +Lactobacillus brevis (40%)+Lactobacillus paracasei (47%) / Lactococcus lactic subs. lactis (36%)+Lactobacillus paracasei (64%) / Lactococus lactis subs. lactis (24,5%)+ Lactobacillus paracasei (28,5%) + Lactobacillus brevis (47%)] Cheese were ripened in 15% saline solution 4 C for 30 days.Samples were taken from each treatment and analyzed on 2nd,15th and 30th days Sensory ,microbiological and chemical properties of the cheese preparations as pH, acidity ,salt,fat,moisture,protein contents during storage period were determined. In this respect effect of using different starter culture combinations on quality of Turkish white chee was determined and Lactococcus lactis subs. lactis(13%)+Lactobacillus brevis (40%)+Lactobacillus paracasei(47%) combination was found as the best and can be suggested as ideal combination for white cheese production.