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Browsing by Subject "rahka"

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  • Luonnollisten antifungaalisten yhdisteiden vaikutus hiivojen ja homeiden kasvuun rahkapohjaisissa tuotteissa 
    Ahervo, Eeva (2015)
    The aim of this thesis was to find a suitable natural antifungal substituent to improve shelf life of quark based products. Antifungal properties were analysed with four different protective cultures: HOLDBAC™ YM-B Plus, HOLDBAC™ YM-C Plus, HOLDBAC™ YM-XPM and FreshQ® 1. Also two different plant based compounds Melinat® and Verdad® F95 were examined. Different dosages and adding methods were used to study the feasibility of these compounds to quark based products. Physical and microbiological factors affecting the shelf life of fresh cheeses, manufacturing processes of cream cheese and quark based products and antifungal properties of both lactic acid and propionic bacteria as well as plant based compounds were reviewed in the literature section. The mixture of milk and quark in elimination tests and cream cheese and quark based spread in following tests were used as samples. The samples were contaminated with two different yeasts, Rhodotorula mucilaginosa and Candida utilis and a mold Aspergillus brasiliensis. The concentration of yeasts and mold were analysed after 0, 7 and 14 days storage at 9 °C. The properties of antifungal compounds were analysed also with the help of chemical and sensory analysis as well as shelf life tests. Protective cultures with recommended dosage were able to inhibit the growth of yeasts in the mixture of milk and quark. A tenfold increase in dosage did not have effect on yeast concentration. HOLDBAC™ YM-B Plus and FreshQ® 1 -cultures added at the same time with fermentation when manufacturing cream cheese and spread samples were not as efficient as potassium sorbate. However, the results from spread samples prepared with post-addition were equal to the results of potassium sorbate. Heat treatment was shown to have a significant impact on the performance of protective cultures. The heat tolerance of protective cultures is needed to investigate in the future so that the adding methods and feasibility especially to heat-treated products would be evaluated more closely.
  • Uudet rahkanvalmistusmenetelmät 
    Heikkilä, Maria (2014)
    The aim of this master’s thesis was to find new and more effective production methods for quarg in Valio as consumption of quarg has increased significantly over the last years. The aim was to produce quarg without the separation of whey so that the raw-materials could be utilised better than with the current methods. The suitability of different milk protein concentrates for quarg production and the effect of different enzymes for the structure of quarg were also examined as was chemical and microbiological fermentation. The utilisation of milk was to be kept low, while the protein content of the quarg was to be maintained at a high level. The aim of the literature review was to become acquainted with the composition of milk, the chemistry of the fermentation of quarg, different production methods for quarg and the functions of different enzymes that modify the structure of milk proteins. The quargs were produced from protein concentrates A, B and C, and were fermented with a microbiological starter, gluconodeltalactone and lactic acid. Enzymes that modify the structure of proteins were added in some of the quargs. Additionally, the effect of rennet on the structure of quarg was examined. Both smooth and grainy quargs were produced in this study. Some of the samples were made in a production plant. The functionality of the quargs in baking was examined in the test kitchen in Valio. The sensory quality and consistency of the quargs were compared with the current Valio fat-free quargs. Acidic whey was not formed when the quargs were produced from protein concentrates, because the dry matter content of the concentrates was as high as the dry matter content in the quargs. The dry matter content of the quargs produced in this study was 15 % and protein content 9 %, on average. The quargs made of protein concentrates had to be homogenised in order to soften their grainy structure. Protein concentrate B was best suited for quarg production because of the mild aroma and the whitest appearance and firmest structure of the quargs. The aromatic quargs made of protein concentrate A and protein concentrate C had a strong off-flavour. The enzyme treatments had no effect on the protein content or the flavor of the quargs but they made the quargs considerably firmer. However, at the same time the graininess of the quargs increased. Microbiological fermentation was preferred over chemical fermentation in order to produce quargs with better sensory features. Without rennet the richness of the quargs decreased. The production of quarg was possible in the production plant. The dry matter content of the quargs was too low for baking applications.

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