SUMMARY
      Wine is the resulting product of grape juice alcoholic fermentation. If a different fruit is used, it should be referred to as “… wine”, using the name of the fruit as a modifier. Wine-making from fruits other than grapes is very popular in many northern European countries where climatic conditions hinder the development of viticulture. The European Economic Community defines fruit wines as the alcoholic beverage obtained by the complete or partial fermentation of fresh, concentrated or reconstituted juices; or pulp maceration with the addition of water, sugar or honey. Once the fermentation process is finished, fresh, concentrated or reconstituted juice can be added. Fruit wines usually have an alcoholic fermentation between 8 and 14 % (gram / 100 mL).
      Wine made from citrus fruit is very popular in Turkey and some Asian countries (China, Japan and Korea). In Argentina, one of the most important citrus-growing areas is located in the area known as the Mesopotamia, specifically on the sandy strip of the Uruguay River bank, in the province of Entre Ríos. The Concordia department in this region is well known for its orange and tangerine production. Newhall, Washington Navel, Salustiana and Valencia are some of the most important varieties.
      In this work some technologies used in oenology were adapted in order to produce orange wine. Every biotechnological process starts with the selection of microorganisms; consequently an ecological study of the native / indigenous flora was undertaken in the aforementioned varieties in order to choose the more adequate species. A strain of S. cerevisaie with good oenological properties was found. As the objective was to prepare musts with fresh juice, pasteurised juice and reconstituted concentrate, this yeast was adapted to each must by determining the respective growth curves. A parallel study was carried out using a commercial strain of S. bayanus. It was found that both yeasts had an acceptable growth in all musts, hence, it was concluded that they could be used indistinctly in orange wine-making.
      Since it was necessary to obtain the native flora in the amounts required for fermentation, they were reproduced in aerobic conditions using batch and fed-batch systems. The highest yields were obtained with the second procedure; as a result this was used to produce S. cerevisiae. The resultant biomass was analysed and it was found that it had excellent technological and hygienic characteristics.
      In order to set up conditions for the fermentation process, work with musts prepared with fresh orange juice, pasteurised juice and reconstituted concentrate, with both yeasts ((S. cerevisiae y S. bayanus), at two fermentation temperatures (10 and 20 ºC), two pHs (their own and another adjusted at 4.0) was carried out following the evolution of some chemical and microbiological parameters from yeast inoculation to the production of young wines. Thus, must component transformation as well as the production of different substances could be observed during alcoholic fermentation. It was also possible to verify microbial spoilage. It should be noted that all orange juice wines made from reconstituted orange juice showed microbial contamination due to the presence of Leuconostoc mesenteroides and Acetobacter sp., therefore they were discarded before being bottled.
      Wines produced with natural and pasteurised juice were bottled and subjected to a maturation process during 120 days at two temperatures (10 y 20 ºC). At the end of this period, physico-chemical and microbiological parameters were further analysed and stability tests were conducted.
      In order to select the most convenient manufacturing conditions for the production of an acceptable orange juice, a full factorial design of 2k type was applied, resulting 16 tests for each strain. It was concluded that with a S. cerevisiae inoculum, the best analytical results were obtained with pasteurised orange juice musts, pH: 4.0, fermentation at 10 ºC and maturation at 20 ºC whereas with S. bayanus, fermentation of pasteurised orange juice must at pH: 4.0, 20 ºC and maturation at 20 ºC should be preferred.