Browsing by Subject "mansikka"
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(2011)Strawberry (Fragaria × ananassa Duch.) is both quantitative and economically most important cultivated berry in Finland. The problem in Finland is low crop yield and short harvest season. During the main season the high supply lower radically the price. The price is highest before and after the main season. Production with everbearing strawberries would give long and even harvest season with more stable price. Everbearing strawberries suit well for table-top production in polythene tunnels with drip irrigation and fertilization. Everbearing strawberries produce flowers and berries during the whole season which affects the nutrient demand. Three different electrical conductivities in the nutrient solution, 1,5 mS/cm, 2,3mS/cm and 3,0 mS/cm, with N:K –ratio 1:1,5 during the ripening, was investigated. The fourth electrical conductivity was 2,3 mS/cm with N:K –ratio 1:2 during the ripening. The vegetative growth, crop yield and quality was evaluated. The amount of drainage water was measures and the amounts of leached nitrogen and phosphorus was analysed. The varieties in the study were ‘Malling Opal’ and ‘Rondo’. Like in previous studies the nutrient demand of strawberry is relatively low. Strongest vegetative growth, highest yield and largest berries was observed with the lowest (1,5 mS/cm) nutrient level. The nutrient level had very little effect on the fruit quality or starting time of the harvest season. The change in the N:K -ratio during ripening did not affect the fruit quality. The uptake of water was highest in the nutrient solution with lowest electrical conductivity. The problem with the water uptake with high electrical conductivity was probably caused by the high ion content in the nutrient solution. The amounts of nitrogen and phosphorus increased significantly in the leaching water with increasing electrical conductivity in the nutrient slution.
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(2013)The use of peat as a growing-medium has raised concerns globally, because it is not ecologically sustainable. Coir is an ecologically friendly alternative, but it is transported very long way to Finland. Therefore, a substitute for peat and coir as a growing-medium in soilless culture is needed. The aim of this research was to find out, whether Finnish plant fibre medium can replace peat or coir in greenhouse production of strawberry. In the experiments four substrates were compared: coir, peat, plant fibre and peat/plant fibre mix. Water holding capacity, pH-buffer capacity and mineralisation of nitrogen were determined, and vegetative and generative growth of strawberries on different substrates were measured. In strawberry cultivation experiment the pH of plant fibre (6,5-7,7) was very close to that of peat (6,4-7,6). Coir and plant fibre had considerably lower pH-buffer capacity than the media that contained peat. The water holding capacity (613 % per dw) of plant fibre was considerably lower than in other media. Plant fibre medium´s water content (32-42 % v/v) was however closest to strawberry´s optimum (25-34 % v/v) during almost the whole experiment. Plant fibre (23:1) and peat/plant fibre mix (29:1) had optimal C/N- ratios in this experiment. The amount of soluble nitrogen was highest in plant fibre medium in the beginning of the experiment. The EC of plant fibre medium was very low in the beginning (0,5 mS/cm), but it increased quickly being 1,2-2,1 mS/cm, so it was second closest to the optimum during the rest of the experiment. The vegetative growth of strawberry plants was more vigorous in peat compared to other substrates. The growth of the root system was weakest in peat. Medium had no significant influence on the amount of yield, and had only minor influence on the quality of the yield. In conclusion, the plant fibre medium could replace peat or coir in the soilless cultivation of strawberry.
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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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(2016)Food adulteration is a constantly growing problem in the quality and safety control of food products. In Finland, the Finnish Customs Laboratory is responsible for the control of imported plant based foods. Among other things, challenging economic situation and gaining economic profit can tempt some people to make adultered products. In a worse case adulteration can cause a serious health risk to the consumer. It’s also misleading when the package doesn’t contain truthful information. Particularly berry jams and purées are easy to adulterate since it’s easy to replace the more expensive ingredient partly with cheaper material, which might be impossible to notice by the sensory characteristics. Strawberry (Fragaria x ananassa) is the most popular and produced berry in Finland. Because fresh strawberry has a short growing season and shelf life, a variety of jams, juices and frozen products are made at home and industrially. Large quantities of strawberry products are also imported into Finland, so there may be some fake products among them. Strawberry contains hundreds of volatile and non-volatile compounds, which are resulted of the plant maturation and metabolism. Some of these compounds are unique to each plant species and also known as marker compounds. The primary objective of this study was to examine the suitability of the selected research techniques for identifying adultered jams by analyzing aroma and phenolic profiles of jams and to develop a preliminary qualitative control method for Customs Laboratory. Techniques used were solid-phase microextraction combined with gas chromatography and mass spectrometry (SPME-GC-MS) to analyse volatile aroma compounds and ultra-high performance liquid chromatography combined with mass spectrometry (UHPLC-MS) for determination of phenolic compounds of self made strawberry jam. Phenolic compounds were extracted by ultrasound assisted extraction prior to UHPLC-MS analysis. Fruits and vegetables used in the jam fraud may be for example apple, pear and pumpkin, so the possible marker compounds were analysed also from jams made of these plants. Self-made fake jams were made by mixing strawberry jam (cultivar Polka) with apple (cv. Ida Red), pear (cv. Conference) and pumpkin (cv. Butternut) jams in proportions of 5–50 % to examine the detection of adulteration. Also some commercial products were analysed to evaluate the suitability of the methods to commercial samples. Results were analyzed and studied by repeatability tests of methods and principal component analysis (PCA). Relative standard deviation (RSD) of the SPME-GC-MS method was considerably higher than RSD of the UHPLC-MS method (51 % compared to 10 %) which tells about weak repeatability of the SPME-GC-MS method. Interesting discovery was the observation of phloridzin from the strawberry samples, since phloridzin has been used as a marker compound of apple although similar observation has been reported earlier. To our knowledge this is the first time phloretin xyloglucoside was also observed from strawberry samples. Self-made strawberry, apple, pear and pumpkin jams differed from each other on the basis of aroma and phenolic compounds composition of the studied cultivars. The aroma profile of apple jam and pumpkin jam differed from each other the most. By the phenolic profile strawberry jam was the most different from the other samples. The mixtures of strawberry jam with apple, pear and pumpkin jams in proportions of 5 %, 10 %, 20 % or 50 % were clearly separated from the self made pure jams on the basis of both aroma composition and phenolic composition. The differences between strawberry jam and fake jams were clear even when the reference jam (apple, pear or pumpkin jam) was removed from the PCA. The 5–20 % fake jam mixtures had only minor differences in aroma and phenolic composition, meaning that determination of quantitative differences with the current methods would be challenging. Mixtures of 50 % stood out the most from other fake mixtures. The evaluation of commercial samples was found to be challenging due to the variability factors of the study. Nevertheless both methods were found to be useful for the detection of adulterated strawberry jams made of selected cultivars. The detection of addition of apple, pear or pumpkin jam was already seen at the addition level of 5 %. With some modification and further development both of these methods can be used as quality control methods at Customs Laboratory.
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(2016)The literature review of this master’s thesis dealt with major and minor mineral composition of strawberries and the factors affecting it. In addition, the effect of jam production on mineral profile and jam adulteration as a phenomenon were discussed as well as using the mineral profile to detect food adulteration using statistical multivariate methods. The aim of the experimental part of this thesis was to study if the mineral profile in combination with statistical multivariate methods could be used to point out the authenticity of strawberry jam. Alterations in the strawberry mineral profile were studied by determining the mineral profile of several different strawberry samples (n = 51). In addition, the strawberry data was used to create models for classification of other samples. The operability of the method was tested using “forged” model jams created by mixing strawberry jam with apple, pear or pumpkin jam (5 %, 10 %, 20 % and 50 %). The differentiation of mineral profiles of other plant species (n = 10) from strawberry mineral composition was tested with small-scale data. Additionally commercial strawberry jams (n = 33) were tried to classify by their mineral profile to be authentic or adulterated. Mineral profiles (Al, B, Ca, Cd, Cu, Fe, K, Mg, Mn, Mo, P, Pb, S, Si and Zn) were quantified with inductively coupled plasma – optical emission spectrometry (ICP–OES). Sample pretreatment included freeze drying, grinding, wet digestion using nitric acid and hydrogen peroxide and dilution with water. Quantification was based on external standard method. Results were processed by principal component analysis (PCA) and soft independent modelling of class analogies (SIMCA). Fabricated model jams and pure apple, pear and pumpkin jams could be separated from strawberry jam both with principal component analysis and with using SIMCA method to classify them to be something else than strawberry jam with 95 percent probability. Most accurate classification was obtained with mineral profiles combining Mg, P, S, Ca and K or Mg, P, S, Mn, Ca and K. Other plant species studied had different mineral profiles compared to strawberries with exception of raspberry. No clear groups were formed on principal component analysis of the strawberry data in respect to cultivar, growth place or time. The method was not yet applicable for the use of classifying commercial strawberry jam samples reliably. There is a need for additional studies about the effect of ingredients used for jam production on the classification. Also the separation between mineral profiles of species related to strawberries should be studied further. In addition mineral profile library of strawberries for industrial processing should be created in order to classify commercial strawberry jam samples. Based on the separation results of fabricated model jams and authentic strawberry jam the method seems to be suitable for further development at least for detecting strawberry jam adulteration by extending with apple, pear or pumpkin.
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(2019)Punaisen värin ruskistuminen on laatuongelma mansikkasoseessa. Mansikan punainen väri on peräisin antosyaaneista, jotka ovat reaktiivisia ja hajoamisherkkiä yhdisteitä. Ruskistumisreaktiot jaotellaan entsymaattisiin ja ei-entsymaattisiin reaktioihin. Kirjallisuuskatsauksessa perehdyttiin mansikan antosyaanien kemiaan ja kartoitettiin mansikkasoseen ruskistumisen eri mekanismit. Kokeellisen tutkimuksen tavoitteena oli selvittää hallintakeinoja mansikkasoseen ruskistumisen estämiseksi. Kokeellinen tutkimus koostui kolmesta osasta: kuumennus-, säilyvyys- ja prosessikokeesta. Kuumennuskokeessa selvitettiin mansikkasoseen kuumennusajan ja värimuutosten välistä yhteyttä sekä tehtiin mansikkaraaka-aineiden vertailu. Säilyvyyskokeen mansikkasosenäytteitä seurattiin kuuden viikon ajan 7 tai 23 C:n lämpötilassa. Prosessikokeessa vertailtiin teollisessa mittakaavassa valmistettujen vadelma- ja mansikkasoseiden värimuutoksia kuukauden ajan. Lisäksi verrattiin kuumennus- ja korkeapainepastörointikäsittelyn vaikutusta mansikan värin pysyvyyteen. Kolorimetrillä tehdyistä värimittauksista määritettiin näytteiden väliset värimuutokset (E*). Värimittauksen lisäksi kaikista mansikkasoseista määritettiin suuntaa antava antosyaanipitoisuus spektrofotometrisellä menetelmällä. Säilyvyyskokeen mansikkasosenäytteiden tarkat antosyaanipitoisuudet ja fenolisten yhdisteiden pitoisuudet määritettiin erittäin suuren erotuskyvyn nestekromatografisella menetelmällä. Lyhyt kuumennusaika (30 s) aiheutti mansikkasoseessa suurimmat säilytyksen aikaiset värimuutokset. Pidemmälla kuumennusajalla (180 s) värimuutokset olivat suurempia kuumennuksen aikana, mutta säilytyksen aikaiset muutokset jäivät pienemmiksi. Kylmäsäilytetty mansikkasose oli näytteistä ainoa, joka ei menettänyt hyväksyttävyyttään säilyvyyskokeen aikana. Prosessikokeessa vadelmasoseen väri osoittautui merkittävästi mansikkasoseen väriä pysyvämmäksi. Korkeapainepastöroidun mansikkasoseen väri oli yhtä hyväksyttävä kuin kuumennetun, mutta rakenteen hyväksyttävyys heikkeni kuukauden säilytyksen aikana. Tulosten perusteella voidaan päätellä, että lyhyt kuumennusaika ei ollut riittävä mansikan endogeenisen entsyymiaktiivisuuden inaktivoimiseksi. Säilyvyyskokeessa ilmeni mansikan antosyaanien suuri hajoamisherkkyys, jota voidaan hillitä vain kylmäsäilytyksellä. Mansikkasoseen kylmäsäilytyksen tarpeellisuus varmistui prosessikokeessa.
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