Browsing by Title
Now showing items 3245-3247 of 3247
-
(2021)Whey is a significant side stream in the cheese making industry, and it can be utilized in several ways especially because whey proteins are nutritionally valuable. Whey cheeses are produced all around the world and mostly in small scale and traditional ways. The production of Ziger whey cheese has a long tradition in Switzerland, and it requires fresh whey derived from rennet-induced cheese making. The whey proteins are precipitated by high manufacturing temperature, the addition of acid and NaCl. The goal of this master’s thesis is to develop a Ziger whey cheese that can be applied in the Finnish dairy industry including optimization of the manufacturing process emphasizing the manufacturing temperature. The thesis also investigates and compares the effect of the temperature on the moisture, protein, and fat content and the yield of the Ziger whey cheese. Also, this thesis aims to examine the effect of the manufacturing temperature on the shelf life by monitoring microbial and physicochemical parameters of the Ziger whey cheese over 21 days of storage. The manufacturing temperatures examined in the production of Ziger were 88 oC and 93 oC, and the production was repeated three times for both temperatures which resulted in altogether six production series. The temperature had a significant effect on the yield which concluded, that the higher the temperature was during the manufacture, the higher the yield was. The microbiological quality was not affected by the manufacturing temperature. However, during the storage there was a significant correlation between the growth of lactic acid bacteria and the pH value i.e., the bacterial count increased as the pH value decreased. After 21 days of storage, every Ziger whey cheese sample crossed the threshold of spoilage for the total viable count which was set at 107 CFU/mL. The manufacturing temperature had no impact on the protein and fat contents. Instead of the manufacturing temperature, there was a strong correlation between the moisture and the fat content. Based on the fat content, the Ziger whey cheese can be categorized as creamy and soft whey cheese. For future reference of research, the quality and shelf life of Ziger whey cheese could be improved by modified atmosphere or vacuum packaging, high packaging temperatures, and shorter drainage time. Moreover, the production could be made more efficient by a continuous process in comparison to batch production.
-
(2022)The physical stability of plant-based beverages is often weak and is used to be improved by food additives. β-glucan and dextran are hydrocolloids that have been found to increase fluid viscosity and therefore may have the potential to replace E-coded hydrocolloids. The aim of this master's thesis was to investigate the effects of oat β-glucan and microbiologically produced dextran on the physical stability of a drinkable oat snack. In addition, the aim was to determine the importance of the molecular size and concentration of β-glucan for its stabilizing ability. The oat base without any added hydrocolloids served as a control. β-glucan and dextran were added to the oat base as extracts so that they replaced a certain volume of oat base water. To determine the concentration effect of β-glucan, an oat beverage containing a high molecular weight β-glucan extract extracted from oat bran was prepared in three different extract concentrations. To determine the effect of the molecular weight, an oat beverage containing an enzymatically hydrolyzed low molecular weight β-glucan extract was prepared. The effects of dextran were studied by preparing oat beverages containing exopolysaccharide extract (EPS) (dextran positive and negative sample). Samples were stored in a refrigerator for 14 days, during which time their stability was characterized by observing phase separation and measuring viscosity, particle size and turbidity. The stability of the beverage samples decreased because of sedimentation, leading to the visual phase separation at the top of the samples. The high molecular weight β-glucan extracted from the oat bran reduced sedimentation and phase separation, and stability and viscosity increased as the extract concentration increased from 5% to 7.5%, with almost invisible phase separation in the latter. Thereafter, increasing the extract concentration to 10% no longer reduced the phase separation, but resulted in a decrease in viscosity during storage. Low molecular weight β-glucan (extract content 10%) did not increase the stability of the oat base, and the viscosity of the sample decreased by about 60% during storage. The decrease in viscosity in these samples may be due to the aggregation of proteins and / or β-glucan due to the higher β-glucan content. The effects of dextran on the stability of the oat beverage remained unclear, as the dextran-positive and negative samples did not differ significantly in viscosity or phase separation, so further studies are needed. Based on this thesis, high molecular weight β-glucan appeared to be a potential substitute for food additives in oat-based beverage applications.
-
(2015)Punajuuren nauttimisella on paljon terveydelle edullisia vaikutuksia. Viime vuosina raaka punajuuri on kuitenkin saanut negatiivista julkisuutta, sillä sen nauttiminen on yhdistetty ruokamyrkytysoireisiin niin Suomessa kuin muualla maailmassa. Vuonna 2010 Suomessa raportoitiin seitsemän raa’an punajuuriraasteen nauttimisesta aiheutunutta ruokamyrkytysepidemiaa, joissa oireet alkoivat ja laantuivat nopeasti. Näiden esiintymien raasteista ei löytynyt tyypillisiä elintarvikepatogeenejä tai niiden tuottamia toksiineja, joiden avulla oireet olisivat selittyneet. Sen sijaan raasteiden havaittiin sisältävän runsaasti Pseudomonas fluorescens -ryhmän bakteereita, jotka tunnetaan elintarvikepilaajina eikä -patogeeneina. Tässä työssä karakterisoitiin ruokamyrkytysten yhteydessä eristettyjä β-hemolyyttisiä P. fluorescens -ryhmän bakteereita ja tutkittiin, voisivatko kyseiset bakteerit tuottaa jotain oireet selittävää yhdistettä. Tämän lisäksi vertailuun otettiin ruokamyrkytyksiin liittymättömistä punajuurista ja porkkanoista eristettyjä fluoresoivia pseudomonaksia. Bakteerien karakterisoinnissa hyödynnettiin niin fenotyyppisiä kuin geneettiseen tietoon perustuvia menetelmiä, kuten kasvua eri lämpötiloissa, kykyä assimiloida eri hiilihydraatteja, entsyymiaktiivisuuksien määrityksiä ja rpoB-geenin sekvensointia. Pseudomonakset pystyvät tuottamaan valtavan määrän erilaisia sekundäärimetaboliitteja, joista tässä työssä keskityttiin tutkimaan syklisiä lipopeptidejä. Syklisten lipopeptidien tuottoon pystyvät bakteerit tunnistettiin PCR-pohjaisella menetelmällä, minkä lisäksi kahden lipopeptidin, tolaasiinin ja WLIP-lipopeptidin, tuottoa tutkittiin spesifisemmillä menetelmillä. Karakterisoinnin perusteella punajuuriraasteista eristetyt, P. fluorescens -ryhmään kuuluvat bakteerit eivät olleet identtisiä keskenään, joten mikään tietty fluoresoiviin pseudomonaksiin kuuluva bakteerikanta tuskin yksinään voisi olla ruokamyrkytysoireiden taustalla. PCR-menetelmällä saatiin viitteitä siitä, että kaikki tutkitut pseudomonakset pystyvät otollisissa oloissa tuottamaan syklisiä lipopeptideitä. Sen sijaan tutkittujen lipopeptidien osalta WLIP-lipopeptidiä tuotti osa bakteereista kun taas tolaasiinin tuotto oli paljon harvinaisempaa. Saatujen tulosten perusteella ei voida vetää johtopäätöksiä siitä, aiheuttivatko P. fluorescens -ryhmän bakteerit ruokamyrkytysoireet, mutta mahdollista se voisi olla ja lisätutkimuksia aiheesta olisi syytä tehdä.
Now showing items 3245-3247 of 3247