Browsing by discipline "Food Chemistry"

The aim of this thesis was to validate the AOAC integrated total dietary fibre method (2011.25) for tomato. Additional purpose of this study was to update dietary fibre values in Finnish food composition database Fineli. The literature review focused on the background of dietary fibre analysis, method development and dietary fibre composition of vegetables. The method measures separately insoluble dietary fibre (IDF), dietary fibre soluble in water but precipitated in ethanol (SDFP) and dietary fibre soluble in water and not precipitated in ethanol (SDFS; oligosaccharides). The method includes a 16 hour starch hydrolyzing incubation that was presumed to stimulate enzyme activity in tomato. The effect of endogenous enzyme activity was examined with preliminary experiments, which included keeping the sample at room temperature before analysis, inactivation of enzymes with heat treatment and performing the analysis without incubation. Repeatability and reproducibility of the method were determined by analysing a pooled sample consisting of Finnish tomatoes. The amount of IDF was highest in samples prepared without incubation. In incubated and heat treated samples, and in samples kept at room temperature the amount of IDF was lower and the amount of SDFP was higher compared to the samples prepared without incubation. This was propably due to pectin depolymerisation and solubilisation by enzymes. Validation sample was prepared without heat treatment. Validation was performed with incubated samples, because standard deviation for non-incubated samples was markedly higher. The amount of TDF (total dietary fibre) in digested samples was 1.3 % (1.1 % IDF and 0.2 % SDFP). Oligosaccharides were found only in trace amounts. Repeatability of the method was 11 % (TDF), 13 % (IDF) and 23 % (SDFP). Reproducibility was 11 % (TDF), 12 % (IDF) and 17 % (SDFP). Repeatability and reproducibility were propably impaired by the inhomogeneity of the sample matrix. Uncertainty of the method was 26 %. The method was validated and proven to be fit for purpose.

Aronia berry consist of possible health promoting anthocyanins of which antioxidative character may have a positive impact to reduce risk factors of cardiovascular diseases. When ingested, anthocyanins decompose to several metabolites of which phenolic acids were the main focus of this research. Phenolic acids can be measured in urine which must be pretreated before further analysis. The aim of the study was to optimize a micro scale solid phase (μSPE) purification method for analysing phenolic metabolites in urine. The method was validated by recovery tests (%). The influence of two acids, formic acid and trifluoroacetic acid, were tested for the recovery (%) of six phenolic compounds: ferulic acid, protochatechuic acid, 3,4-dihydroxyphenylacetic acid, hippuric acid, homovanillic acid and cyanidine-3-glucoside. The method was applied to selected spot urine samples of a clinical research with subjects who had ingested for four weeks 100 ml of aronia juice which contained 1 g of phenolic compounds. Three unknown compounds (A, B and C) were identified as possible derivatives of phenolic acids by UHPLC-MS. The research was part of an EU supported BACCHUSproject. μSPE had a purifying effect with the two acids used having a different influence to the recovery of test compounds. However, there was no clear evidence that either of the acids would be better suited for the purification of the phenolic acids used in this study. Two of the three unknown compounds in randomly selected urine samples were identified as possible derivatives of phenolic acids based on their chromatographic and spectrophotometric characters. Compound A was identified as protocatecuiq acid derivative and compound C was tentatively identified as a derivative of ferulic acid. Compound B instead was not identified because it did not have any typical attributes of phenolic acids.

The usual dietary sources of vitamin B12 are animal-based foods such as meat, milk, fish and shellfish. Vitamin B12 is an essential water-soluble vitamin for humans, which have many necessary tasks in human body. People who lack animal foods like vegetarians and vegans might be at risk of vitamin B12 deficiency. Microorganisms are the only original sources of vitamin B12 in nature. Especially Propionibacterium freudenreichii synthesizes active form of vitamin B12 for humans. P. freudenreichii is GRAS -graded bacteria and it is safe to use in food matrices. Recently, it has been used for natural fortification of vitamin B12 in plant-based products by fermentation. However, the bioaccessibility of vitamin B12 of those products in human body is not very well known. In the beginning of the study, stability of different B12 vitamers were studied in different light and pH conditions. Vitamin B12 forms are very light-sensitive, especially its physiological forms methyl- and adenosylcobalamin. The aim of this research was to study bioaccessibility of vitamin B12 from P. freudenreichii cells and selected food products using a static in vitro assay. After the in vitro model, vitamin B12 content was analysed with UHPLC system. In addition of bacterial cell samples, bioaccessibility was studied also in some food samples, like bread, pasta and spray-dried powder, fortified with P. freudenreichii cells. In vitamin B12 stability studies, red light seemed to improve the stability of B12 forms. In yellow light methyl- and adenosylcobalamin degraded after 15 minutes. In red light they were detectable after hours of exposure. Methylcobalamin seems to be the most sensitive form of vitamin B12 vitamers. The study revealed that the bioaccessibility of B12 was very small (1,5 %) in P. freudenreichii cells but over 50% in whole bacterial broth. Heat treatment for the samples improved the bioaccessibility to some extent. In B12 fortified food samples, the bioaccessibility of B12 was very good (>70 %). The number of heat treatments and food structure could be one reason why bioaccessibilities in food samples are better than in cell samples. According to this research, in situ fortified food products could be a promising source of vitamin B12 in future.

Wines are treated to ensure their quality and preservation in the winemaking process. Treatments also have their drawbacks. Premium winemakers have often avoided filtration because it is supposed to cause a loss of taste. Sulfurization of wine is important, for example, for microbiological quality, but it is assumed to reduce the fruity aroma of wines. The purpose of the literature section was to investigate in general the effects of the wine-making process on the volatile compounds of wines. The interest was to find out what happens in winemaking and what compounds are formed at different stages of the process. The literature section also looked at volatile compounds, their analytics and SPME technology. The aim of the experimental part of the work was to develop a research method using headspace-solidphasemicroextraction-gaschromatography-massspectrometry (HS-SPME-GC-MS) technology and to find out the aroma composition and possible differences of the receiving sample and the bag-in box (BIB) -packaged wine. Indicator compounds for volatile compounds were determined from Chardonnay and Cabernet Sauvignon wines using the HS-SPME-GC-MS method developed for the study of Cabernet Sauvignon wine. In the optimization of the method, the functionality of SPME fibers, the GC temperature program and the sample preparation were studied. Receipt, tank, and BIB packaging samples were collected for examination of the wines. The samples were analyzed by HS-SPME-GC-MS and the results were processed by principal component analysis (PCA) as well as other statistical methods. Receipt and BIB packaging samples from Cabernet Sauvignon wine were not divided into clear groups based on PCA. The model best describing the changes in the compounds was achieved with the profile of volatile compounds: ethyl acetate, 1-propanol, isoamyl alcohol, 2-methylbutanol, butanoic acid ethyl ester, isoamyl acetate, hexanol, hexanoic acid, octanoic acid ethyl ester and octanoic acid. In Cabernet Sauvignon wine, almost all the amounts of volatile compounds remained fairly constant as the process progressed. In 1-propanol, ethyl ester of butanoic acid and ethyl ester of octanoic acid, a decrease in the amount was observed between the receipt sample and the BIB packaging sample. In contrast, the amount of 2-methylbutanol and octanoic acid increased when receiving and BIB packaging samples were compared. Receipt and BIB packaging samples of Chardonnay wine were distinguished by PCA. The model best describing the changes in the compounds was achieved with the profile of volatile compounds: ethyl acetate, isoamyl alcohol, 3-methylbutanol, 2-methylbutanol, butanoic acid ethyl ester, isoamyl acetate, hexanol, hexanoic acid, benzene alcohol, octanoic acid ethyl ester, octanoic acid ethyl ester, octanoic acid ethyl ester. The amounts of volatile compounds studied in Chardonnay wine remained fairly constant. Octanoic acid ethyl ester, benzyl alcohol and decanoic acid decreased as the process. The results of the study show that the wine processing process affects the flavorings of Cabernet Sauvignon and Chardonnay wine. The HS-SPME-GC-MS method showed a reduction in several compounds, but previous studies have shown that this change has not been detected by sensory evaluation.

The literature review focused on the chemical properties of Fusarium mycotoxins and their masked forms, analytical methods for their determination and the toxicological and legislative aspects. In the experimental study, a multi-method was developed and validated for the simultaneous quantification of several Fusarium toxins and their masked forms in barley, oats and wheat using liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique. The simple “dilute-and-shoot” sample preparation procedure was applied, where the extraction was performed with a mixture of acetonitrile, water and acetic acid (79:20:1, v/v/v). Moreover, the aim was to obtain new data on the occurrence of the masked mycotoxins in barley, oats and wheat by analysing 95 cereal grain samples. The type A trichothecenes T-2 and HT-2 toxins (T-2 and HT-2) and the type B trichothecenes deoxynivalenol (DON) and nivalenol (NIV) as well as zearalenone (ZEN), together with 11 masked forms of them, were included based on their importance for the food safety in northern Europe. The analytes were separated on a reversed-phase column and detected in selected reaction monitoring (SRM) mode. Better peak shapes for the early eluting compounds and shorter analysis time were obtained with acetonitrile than methanol as the organic phase, thus it was chosen for the method. The method was validated according to the criteria set in the legislation. The limits of quantification varied from 0.3 to 15.9 ?g/kg. The recoveries were 92?115%, thus being within the tolerable ranges established in the legislation. The inter-day precisions (4?27%) were under the maximum permissible values. Therefore, the method proved to fit for the purpose. In this study, occurrence data on the masked mycotoxins in Finland were obtained for the first time. The presence of ZEN-16-glucoside (ZEN-16-G) and NIV-3-glucoside (NIV-3-G) were reported for the first time worldwide in some of the cereals. The most frequently found toxins were DON, NIV and HT-2. All of the masked mycotoxins included in the method were determined, the most common being DON-3-glucoside (DON-3-G), HT-2-glucoside (HT-2-G) and NIV-3-G.

Pulled Oats preparations are a new plant protein source that contain oats, pea and faba bean. People have been hyping this high-quality protein product but there may be a concern about possible naturally occurring compounds, which can deteriorate the health of sensitive individuals. The literature review deals with the chemical properties, analytics, health effects of FODMAPs (fermented oligo-, di- and monosaccharides and polyols), vicine and convicine but also different treatment methods to reduce their concentrations. In the experimental work the concentrations of antinutrients were analysed and the bases of enzyme treatments were investigated to aid future research in reducing antinutrients in Pulled Oats. Three different samples from the Pulled Oats and four samples from the company X´s processes were analysed. The FODMAPs were analysed using water extraction and HPAEC-PAD (high performance anion exchange chromatography connected to a pulsed amperometric detector). The vicine and convicine were analysed using perchloric acid extraction and HPLC (high performance liquid chromatography). For the enzyme treatments, the samples were extracted and the supernatant was used for incubation. Two different kinds of α-galactosidase were used to decrease the amounts of FODMAPs and β-galactosidase was used to reduce vicine and convicine amounts. Pulled Oats contained FODMAPs and this can cause problems in the digestive system especially for people who suffer from IBS (irritable bowel syndrome). Pulled Oats also contained some vicine and convicine, which can be harmful for individuals lacking G6FD (glucose-6-fosfate dehydrogenase). The amounts of antinutrients did not decrease during the Pulled Oats´ process whereas in the company X´s process they did. The enzyme treatments in laboratory conditions were effective for reducing the amounts but in the Pulled Oats´ processing conditions the result was not significant. The best way to eliminate the antinutrients could be enzyme treatments in the company X´s process. This study gave valuable knowledge for future investigations.

Microalgae are promising raw materials for food- and biotechnology because they contain a lot of proteins, unsaturated fatty acids, pigments, vitamins and minerals. There are few studies on vitamin B in microalgae and some of them are based on partly inaccurate methods. Microalgae in general, analytical methods regarding their analysis and how they use vitamins were discussed in the literature part of this thesis. The structures, chemical properties and occurrence in foods as well as commonly used analytical methods of the vitamins in question were presented. The aim of the experimental part of this thesis was to analyse commercially marketed microalgae supplements (Chlorella sp. and Arthrospira sp. (spirulina)) and laboratory-grown microalga (Euglena gracilis) as potential sources of folate, niacin, vitamin B2 and B12. Contents of vitamin B12, B2 and niacin were analysed using UHPLC method separately validated for each vitamin. The total folate content was analysed microbiologically and folate vitamers by using UHPLC. The vitamin B12 was analysed microbiologically and the active forms of vitamin B12 were confirmed using LC-MS. Acid hydrolysis was used in analysing niacin content. The total folate content in chlorella supplements was of the same order when analysed microbiologically or with UHPLC. Instead, in spirulina supplements the microbiologically analysed total folate content was higher than the total folate content based on the sum of folate vitamers analysed with UHPLC. At most, the total folate content of E. gracilis -sample was 3-fold higher than in commercial microalgae supplements. Especially in spirulina supplements, the vitamin B12 contents were clearly higher when analysed microbiologically than they were when analysed with UHPLC. The difference was most likely due to pseudocobalamin that resembled vitamin B12. On average E. gracilis -samples had higher vitamin B2 content than the commercial supplements. E. gracilis -samples and chlorella supplements contained more niacin than spirulina supplements. According to this thesis, commercially marketed microalgae supplements contained different amounts of vitamin B. Chlorella sp. was proved to be a great source of folate, vitamin B12 and niacin and moderate source of B2. The majority of vitamin B12 in Arthrospira sp. (spirulina) was pseudocobalamin. Despite that, spirulina supplements proved to be a moderate source of vitamin B12. On average, E. gracilis had the highest vitamin B content and it would potentially be an excellent source of vitamin B – if it was accepted for food use.

The literature review described the importance of folate enhancement to human health especially to coeliac patients with an introduction to folate analysis, pseudocereals and possible fortification methods. The aim of this study was to study the natural folate enhancement methods in pseudocereal matrix. Pseudocereal materials consisted of buckwheat, amaranth and quinoa, each of which was subjected to three different treatments: germination, fermentation and combined treatment. Total folate determination was based on an official microbiological assay method (Lactobacillus rhamnosus ATCC 7469). Germination of pseudocereals lasted for 4–5 days. Fermentation was conducted using either baking yeast Saccharomyces cerevisiae ALKO743 or LAB Streptococcus thermophilus ABM5097. All germinated whole grain pseudocereals indeed showed a significant increase in total folate content. Specifically, the increase was 5.4-fold in buckwheat, 5-fold in amaranth and 2.6-fold in quinoa. Fermentation of native pseudocereals also enhanced total folate level. As for the combined treatment, the total folate level of germinated seeds did not further significantly increase or decrease in later fermentation period. Although more studies are needed for processing real pseudocereal foods, our study showed great potential of folate enhancement using germination or fermentation.

The literature review of this master’s thesis dealt with the chemical and nutritional properties of lactose, lactose content in food and methods used for lactose determining. The aim of the experimental part of this thesis was to develop, validate and implement a sensitive and reliable method for determining residual lactose in different kinds of foods using high-performance anion-exchange chromatography and pulsed amperometric detection (HPAEC-PAD). The method was developed for MetropoliLab in response to an increased demand. The matrices chosen for validation were food products that were known to contain traces of lactose: lactose-free skimmed milk, whole milk, banana flavoured yoghurt and cottage cheese. Lactose was extracted in water from a homogenized sample. Proteins were precipitated with Carrez-reagents and the extract was then purified by solid phase extraction and filtration. A strong anion exchange column with quaternary ammonium ion groups was used to separate lactose from other compounds found in the foods and a pulsed amperometric detector equipped with a gold electrode was used for the detection of lactose. The biggest challenges were to remove all compounds interfering with the detection of lactose and to separate lactose from other compounds oxidized at the gold electrode. The sample preparation and the solvent gradient used showed good resolution for lactose. The method was found very sensitive and selective and the whole range of measurement up to 40 mg/100 g was linear. Repeatability, reproducibility and accuracy of results were good. The measurement uncertainty of the method was 11—22 %, depending on the sample matrix. The method development and validation were completed successfully using different kinds of dairy products as sample matrices. Validation for other food matrices was started immediately and the experiments have already shown some promising results indicating the method’s suitability for meat, bakery and convenience food products. In spite of the simple sample preparation step the method is time consuming when analysing large sample arrays and options to overcome it are necessary to examine.

Honey is viscose nutrient solution which is produced by honey bees from the nectar of the plants or excretions of plant sucking insects. For food use honey is collected from beehives in honeycombs which are centrifuged and the separated solution is canned. Honey consists mainly of carbohydrates and water but there are also in small amounts numerous other compounds such as proteins, vitamins, organic acids and phenolic compounds. Most of the carbohydrates in honey are fructose and glucose but also a great number of di-, tri-, and oligosaccharides can be found in smaller amounts. Composition of honey and therefore the carbohydrate profile can vary greatly depending on the honeys botanical origin, soil, climate and other factors affecting the growing environment. The goal of this study was to develop a chromatographic method using high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) to determine carbohydrate profiles for domestic unifloral and mixed honeys. Principal component analysis (PCA) was used to investigate the differences in determined carbohydrate profiles. Equipment used in this study consisted of chromatographic separations module, electrochemical detector and Dionex CarboPac PA1 column. Milli-Q water, 100 mM sodium hydroxide solution and 100 mM sodium hydroxide solution with 0,5 M sodium acetate buffer were used as eluents. 33 domestic unifloral and mixed honeys of 12 different botanical origins were used as samples. Approximately 0,5 g of samples were weighed in three replicates to 50 ml volumetric flasks which were filled with Milli-Q water. From these solutions 1:5 and 1:200 dilutions were made and they were filtered to HPLC vials through 0,45 µm PVDF-filter before analysis. Carbohydrates in samples were identified using a standard mixture with 16 carbohydrate standards. Carbohydrates were quantified from chromatograms using the height of detected peaks. Ten different carbohydrates could be separated from the honey samples for determination of carbohydrate profiles. Most of the samples contained fucitol, fucose, glucose, fructose, turanose, nigerose and maltose. Some samples contained also trehalose and rhamnose. Raffinose was quantitated from one honeydew sample. In addition melezitose/isomaltose, kojibiose/1-kestose and β-gentiobiose were detected in samples but quantitation of these carbohydrates could not be done because of poor resolution. Concentrations of the quantitated carbohydrates varied greatly even between honey samples of same botanical origin. PCA revealed that honeydew honeys differed clearly from other unifloral honeys according to their carbohydrate profiles. The PCA model explained circa 64 % of variance in the whole dataset. Differed honeydew samples were removed from second PCA model. In this model Himalayan Balsam, cloudberry and willowherb honeys could be separated as individual groups from the other unifloral honeys. This model explained circa 40 % of variance in the whole dataset. However in PCA most of the unifloral honeys formed a group where no clear differences could be assessed between samples of different botanical origin. Moreover some samples aroused a suspicion over their actual botanical origin. The developed method could be used to separate honeydew honey samples from blossom honey samples. The differences among other unifloral honey samples were not clear although some of the unifloral honeys showed some signs of unique carbohydrate profile. On the other hand the number of samples used in this study was quite small. Therefore strong conclusions about the differences among carbohydrate profiles of different unifloral honeys could not be made. For future research greater number of samples is required in order to verify the potential differences found in this study.