Browsing by department "Elintarviketeknologian laitos"
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(2009)The objectives of this study was to investigate the cause of the local whiteness in AURAÒ blue cheese and to find the way which reduces the white cheeses. It was studied if white cheeses have a compact or open structure. White cheeses were classified as compact and open. Scanning electron microscopy was performed on compact, open and mouldy cheeses. Factors which cause compact cheese were also studied. At the beginning of blue cheese manufacturing, citrate was analysed at different time points in different vats. The aim was to make compact cheese in one of the trials. Cheese curd was broken before and after moulding. Alternative factors including the effect of addition of salt to the vat on reducing the amount of white cheeses was also studied. Other variables were the speed of the drying belt, heating of vat, the amount of vat whey and the different moulds were also studied. In addition it was studied how separation of whey affects to the amount of compact cheeses in the drying belt. Microbiological and chemical analyses as well as density and texture measurement were performed on the trials. Most of the white cheeses were compact and the small amount of white cheeses had an open structure. The compact cheeses had less mould and yeast than the mouldy cheeses. The pH was lower and the amount of free amino acids was less in the compact cheeses than the mouldy cheeses. The compact cheeses were more dense than the mouldy cheeses. Measurements from texture analyser showed that the hardness of compact cheese were greater and the fracturability of compact cheese was lower than the hardness or fracturability of mouldy cheese. There were no differences in the amount of citrates between days or vats. Broken cheese curd before moulding caused a more compact structure. The addition of salt in the vat did not affect the white cheeses. The compact cheeses decreased when the speed of the drying belt was reduced. With the use of the new mould, less compact cheeses were produced than with older mould. The removal of water from cheese curds is logarithmic the longer they are on an open drying belt. The compact cheese also decreased logarithmically when cheese curds were on drying belt from zero to ten seconds. There was a greater amount of compact cheeses after moulding in the vat.
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(2009)The present study was conducted to test the effect of an essential oil blend containing thymol and cinnamaldehyde on chicken pancreatic enzyme activities. Essential oils are oils from plant origin and have become an important alternative in animal nutrition after the European Union banned the use of antibiotics as growth promoters. Some previous studies have indicated that essential oils may stimulate the secretion of digestive enzymes, and thereby have a positive effect on the digestion and absorption of nutrients (Windisch et al. 2008). Pancreas samples originated from 20- and 28-day old Ross male chickens, that were fed with wheat soybean diets supplemented (or not) with the essential oil blend. Optimization of the colorimetric assays for detecting the enzyme activities in the supernatants of pancreatic homogenates was carried out. The ?-amylase, trypsin, chymotrypsin and lipase activities were expressed as U per mg of protein. The activity results were compared with previously collected digestibility and performance results. The addition of the essential oil blend at the applied concentrations to chicken diet did not have a significant effect on the activities of the chicken pancreatic enzymes. Overall, the enzyme activities did not show strong correlations to chicken performance or nutrient digestibilities. However, there were significant differences (P < 0.05) in the lipase and trypsin activities between the 20- and 28-day old chickens. It can be concluded that the studied essential oil blend did not stimulate pancreatic enzyme activities at the tested conditions. However, further studies are needed to explain the effect of the dietary supplement of essential oils on chicken digestion.
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(2009)The literature review of this thesis deals with light, different light sources and their properties. LED (Light Emitting Diode) light was specially taken into consideration, because the use of LED lights will increase in general illumination. The literature review also deals with the quality changes of dairy products and potatoes caused by exposure to light. The aim of this study was to search for such a spectral distribution of light which would cause only minor changes in the sensory quality of milk and the surface colour of potatoes. Objective was to also find out if there is a difference between the effects of fluorescent light and LED light on the quality of milk and greening of potatoes. Reduced (1,5 %) fat milk and new potatoes were used as testing materials. The milk in commercial carton board packages was exposed to six different light sources: white fluorescent lamp, white LED and LED of four different colours. The potatoes packed in transparent LDPE (Low Density Poly Ethylene) bags were stored under five different light sources: white fluorescent lamp, white LED and LED of three different colours. The light intensity at the surface of the packages was about 1000 lx in both studies. In the milk study, the effects of light were evaluated with a sensory method using descriptive analysis. In the potato study, the light effects were analysed with colour measurements (avalue) using a spectrophotometer and with surface temperature measurements using a laser thermometer. Sensory evaluation of milk there resulted in few statistically significant differences in the intensity of the attributes between the milks stored under different light sources. Light exposure caused a rapid greening of potatoes in every illumination. According to colour change percentage, the greening order under different lights was: white LED < yellow LED < green LED < turquoise LED < fluorescent light. The potatoes which were stored in dark had no change in their surface colour. The surface temperature of potatoes increased most under white LED and turquoise LED lights. A spectral distribution of light which would have caused less changes in sensory quality of milk than commonly used fluorescent light was not found in this study. The results showed, however, that in addition to blue light which has always been considered the most harmful for milk the red light also caused remarkable quality changes. Based on the results of this study, it could be suggested that under the LED lights the quality of packed milk retained its quality characteristics at least as well as under the fluorescent light. There were differences between the effects of different lights on the greening of potatoes. White and yellow LED light caused less greening of potatoes than the other lights. The strongest greening of potatoes was observed under the fluorescent light.
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(2009)The literature review of this thesis deals with light, conventional light sources and the effects of light on the quality of foods. Impacts of light on the quality of frozen foods were also discussed. Effects of fluorescent light on frozen food have been previously reported in the literature, but effects of LED light have not. The literature review also deals with the quality changes of foods caused by freezing and frozen storage. The significance of package during frozen storage was reviewed. The aim of the experimental study was to investigate whether there are differences between the effects on frozen food when exposed to fluorescent or LED light. Frozen strawberries, shrimps, lamb loins and ice cream were exposed to fluorescent and LED light for 4 weeks. The samples were packed in transparent LDPE pouches except the lamb loins, which were vacuum-packed in transparent PA/PE film. References were packed in aluminium foil. Temperature of the samples was monitored by the sensors attached to the surfaces of the packages. The colour of the samples was measured every week using a spectrophotometer. Thiobarbituric acid (TBA) values of the shrimps and lamb loins were analysed after 0, 2 and 4 weeks of exposure. The odour of shrimps was evaluated with sensory evaluation using a multiple comparison test. Sensory evaluations of ice cream was conducted by trained panelists using a multiple comparison test. All the sensory evaluations were conducted after 2 and 4 weeks of exposure. In addition, ice cream was exposed to light under a yellow plastic film to find out the effects of riboflavin, which is known to operate as a sensitiser. After 4 weeks of exposure to the fluorescent light the total colour difference of the samples was higher than that of the products exposed to the LED light. Differences were pronounced especially in ice cream exposed to light under transparent film. The smell and taste of ice cream were affected when exposed to light under transparent or yellow plastic films. There were no statistically significant differences in the taste of ice cream when exposed to fluorescent or LED light for 4 weeks, but the smell of ice cream appeared to be more divergent from the reference when exposed to LED light under transparent film for 4 weeks than the smell of ice cream exposed to fluorescent light for 4 weeks. On the basis of this study, fluorescent light affected the colour of the frozen food more than LED light. Light sources did not differ from each other, when the results of the sensory evaluation of shrimps were considered. Because TBA values of lamb loins and shrimps also increased in reference samples, the effects of light could not be separated. Sensory properties of ice cream were affected by light exposures, but on the basis of sensory evaluation it is not possible to state which light source was more detrimental to the quality of ice cream.
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(2009)Greenhouse cucumber (Cucumis sativus) is one of the most important vegetables in Finland with annual consumption of about 30 million kilogrammes. The cucumber itself generates ethylene at a low level, but excessive ethylene concentrations (>0.5 ppm) in ambient air causes quality losses, like yellowing and softening. The problem is that cucumbers often share the same airspace with ethylene generating fruits and vegetables during transport, storage and sale. The literature review deals with ethylene synthesis and its effects in vegetables. Also, ethylene measurements and detection, as well as ethylene exhaustion, and inhibition are discussed. The aim of the experimental study was to find the best available packaging material for greenhouse cucumbers. From 13 different packaging alternatives, studied in a preliminary test, the most promising were selected for storage experiments. Cucumbers were cultivated in greenhouses in SouthWest Finland. Packed cucumbers were stored at 12 ºC and in airflow with 1 ppm ethylene for 14 or 7 days for the first and second trial, respectively. Analyses were performed once a week. They consisted of O2and CO2concentrations of packages and sensory quality of whole and sliced cucumbers. Cucumbers were also photographed. Results showed that cucumbers packed in low oxygen transmission film deteriorated fast, whereas too many holes in a package resulted in high weight losses. Cucumbers packed in shrinkwrapped PEpackages with micro holes had lighter green colour than other cucumbers after 13 days. Cucumbers packed in biodegradable film had nearly 25 % weight loss after 27 days compared to other packages causing weight loss of 3 %. After 13 and 21 days’ storage time the freshness of taste was better if the PPpouch with an ethylene scavenger was used. The currentlyused shrinkwrapped PEpackage with micro holes proved to be a good choice for cucumbers if there is no risk of ethylene in food chain. If ethylene is present, it is better to use a PPpouch with micro holes. In that case, additional benefit of improved freshness of taste can be achieved by using ethylene scavengers.
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(2007)The literature review deals with the composition of rye flour and the significance of en-zymes and sourdough in rye flour processing. The operational principles of twin screw extruders, the extrusion of grain based materials and the formation of aroma during grain based extrusion are also reviewed. The aim of this study was to determine the influence of the amount of powered rye sourdough and extrusion cooking parameters on the structure and properties of rye extrudate. Three process parameters were varied: content of rye sourdough powder, process temperature during the final stages of extrusion and revolution speed of the extruder's screws. A Box-Behnken's experimental design was used with 3 levels of dried sourdough powder content (0, 20 and 40%), 3 screws revolution speeds (200, 350 and 500 rpm) and 3 exit temperatures (120, 150 and 180°C). Feed rate was set at 4.0 kg/h and the moisture of the feed was 17.4%. A total of 15 experiments were perfomed. Pasting properties, acidity, acid value and D- and L-lactic acid concentration of full grain rye flour, dried rye sourdough flour and ground extrudate powder were determined. Acetic acid concentration of dried rye sourdough powder was also determined. Moisture content, expansion, texture, bubble sizes and colour of extrudate were determined. Extrusion cooking produce very different types of rye extrudates and the effect of process parameters on structure of extrudate was significant. When the pressure at the die was 30–40 bar, structure of extrudates were porous. Freeze dried extrudates were harder than extru-dates stored for one day at room temperature. Young's modulus decreased with increasing screws speed and processing temperature. Extrudate’s expansion increased as a function of increased revolution speed of screws and decreased processing temperature. As the content of dried sourdough increased, the bubble sizes of extrudate increased and also yellow (a) and red (b) colour and acidity of extrudates became stronger. Lightness (L) was statistical significantly higher when temperature was higher. As expected, the concentration of D- and L-lactic acid increased with increasing dried sourdough content. Decreased content of dried rye sourdough and slower revolution speed of screws increased cold peak viscosity signifi-cant. Peak and hold viscosities increased with slower revolution speed of the screws and decreased content of dried sourdough. Final viscosity and setback value increased signifi-cantly with slower revolution speed of the screws. The optimal extrudate, which was crispy and had a good flavour, was obtained when the content of dried sourdough powder was 20%, revolution speed of the screws was 500 rpm and processing temperature was 120°C.
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Tuotantotekniikan ja säilytysajan vaikutus kasvihuonekurkkujen ja -tomaattien aistittavaan laatuun (2008)Finland has moved from growing vegetables by natural light to year-round greenhouse production using artificial lighting. Determination of sensory effects on greenhouse-grown vegetables is important as sensory evaluation provides information which chemical methods can not. It can tell us about the quality of samples which affects the consumers' behaviour. There are different opinions on how the quality of vegetables should be determined. The consumers are dissatisfied with the quality of vegetables and fruits, although the variety of products is larger than ever. The aim of this study was to find out how artificial lighting contributes to the sensory quality of greenhouse tomatoes and cucumbers compared to traditional natural lighting, and how storage affects the sensory attributes of the samples. In this study there were two sets of tomatoes and two sets of cucumbers, representing two different harvest seasons. Sensory evaluation involved two steps. The first step was to sort the samples and the second step was to generate a profile using descriptive analysis. Sorting was found to give some approximate information on differences between tomato and cucumber samples. MDS-maps dimensions were presented by age and lighting technique. The reliability of sorting results was quite good. The quality of the natural products was inconsistent. Production technology had more of an effect on cucumber samples than tomato samples. Natural light cucumbers were, for example sweeter and softer than artificial light cucumbers. Age had an especially large effect on cucumber appearance characteristics. There were less differences between tomato samples than cucumber samples. Production technology had less of an effect on tomato samples than age, e.g. hardness decreased during storage. In this study, it was found that artificial lighting has little effect on the sensory quality of Finnish greenhouse tomatoes compared with tomatoes grown under natural light.
Now showing items 1-7 of 7