Browsing by discipline "Elintarviketeknologia"

Alkaline phosphatase (ALP) is an endogenous enzyme found in milk, which is inactivated at higher temperatures than vegetative bacteria and is thus used as an indicator of a successful pasteurisation. The ability of ALP to reactivate allows it to be found in milk products that are claimed to be pasteurised. The aim of this Master‘s thesis was to understand the reactivation behaviour of ALP in order to ascertain whether high levels found in milk products are correlated to a normal reactivation property of the enzyme or other possible reasons, such as a failed pasteurisation or contamination. This work also aimed to define the mean ALP activities found in specific commercial milk products and their deviation from the acceptable levels. Another scope was to determine the freeze stability of ALP to define its appropriateness for post-stored analysis. Lastly, the examination of ALP location in milk fat membrane globules was examined to interpret the variation of enzyme activity levels in products of different fat content. The experimental part of the Master‘s thesis was divided into three parts. The first part included the record of ALP activities of different commercial Finnish milk products which are analysed in different groups according to their fat content and product type. The second part concentrated on the heat-treatment of milk samples at different time-temperature relationships and followed the reactivation behaviour of ALP. The total micro-flora was taken into consideration in order to observe any relation between the increased ALP activities and microbial growth. ALP activities were measured by a fluorimetric method, a quick three minute method which has the advantage of being more accurate compared to colourimetric methods. The third part examined the fraction in which ALP activities are found in milk after separation and its freeze stability when stored at -79 ºC. Commercial cheeses showed a high ALP activity in Emmental thermised cheeses and an activity less than 10 mU/g in other cheese types and pasteurised cheeses. In commercial milks, UHT treated and those closer to expiration date, high ALP activities were found, while pasteurised milks had low activities below the higher acceptable levels. The reactivation property of milk samples that were heat-treated in ALP was not related with the microbial growth and was quicker when the milk samples were heat-treated at higher temperatures. After the separation of cream from whole milk samples, ALP activity was found in the skim milk part. In conclusion, ALP activities did not decrease significantly following freeze storage for a few days showing its stable freeze properties.

There is growing concern about the world population growth and the sufficiency of protein resources. Edible insects could be an alternative protein source for human beings. The aim of this master thesis was to examine the sensory characteristics of a new home cricket (Acheta Domesticus) product and understand the attitudes of consumers towards edible insects. The aim was to investigate the impact of consumer familiarity with edible insect food products on purchase intention and expected liking. The roles of media trust and purchase activism were expected to affect the behavior of consumers. Besides these four indicators also two more were added. These were food neophobia scale and innovativeness. The data on consumer attitudes and perception towards insect food was collected by using an electronic form that was sent to different mailing lists. Total of 167 respondents were gathered, 141 women and 63 men. 53 participants attended the sensory analysis tests on the beginning of the year 2020, ages 18 – 62. The analysis of the data was done with SPSS Statistics version 25. The findings of this study indicate that consumer familiarity contributes to purchase activism, purchase intention and expected liking. In this study the media trust did not contribute. Food neophobia scores correlated negatively to the intention to buy, expected liking and willingness to recommend the product. Innovativeness correlated positively to intention to buy and expected liking, and as expected, innovativeness correlated negatively to food neophobia scores. As people learn more about the ecological and nutritional benefits of edible insects, their attitudes towards insect food become more positive and they are more willing to try and taste insect products. The new home cricket product, PANNU Sirkka by GRiiDY, turned out to be quite suitable for Finnish consumers taste. On the just-about-right scale (1–4) the average score was 3,3 – 3,8 of all the assessed attributes. Many of the open responses mentioned the product to be ‘tasty, delicious, surprisingly good and crispy’, for instance. To overcome the preconceptions of western consumers, there should be more occasions to try and taste insect food. Marketing efforts are best targeted to consumers who are neophilic and innovative and encourage them to be the early adopters of insect food.

Milk foam is an essential part of coffee drinks such as cappuccinos. The foaming properties of milk can change during its shelf life. Milk used in coffee usually contains at least 2 % fat which can deteriorate its foaming properties. UHT milk can lose its sensory and foaming properties during its shelf life. In this thesis the change of properties of UHT-treated coffee milk called Barista milk were investigated. Barista milk is a commercial lactose free, homogenized milk meant to use with coffee. It has 2,0 % of fats and 3,5 % of proteins. The preservation of UHT barista milk was studied when milk was 4, 5, 6 and 7,5 months old. The foaming properties of barista milk were evaluated with automated foaming system. The volume of foam and its stability were measured as volume in a measuring glass. The structure of foams was also photographed and analyzed from photos. Nowadays plant-based drinks are important options for milk. Selected oat drinks for coffees were studied with same foaming methods as milk samples. The oat drink samples were kept in room temperature, fridge (+6 °C) and + 30 °C storage conditions. The tests were made when samples were 4, 8 and 10 months old. Barista milk as evaluated also with sensory evaluations. The sensory properties of barista milk were measured by tasting the milks referred to a fresh reference milk. Sweetness, bitterness, intensity of cooked flavor and fullness were evaluated from milks and cappuccino drinks made from the studied milks. In addition, a professional barista foamed the milks to makes cappuccinos and the drinks were evaluated. The preservation of milk did not affect its foaming properties or foam stability significantly. The foaming temperature affected the volume of foam more than the age of the milk. There was a slight change in the bubble structure of milk. The bubble structure was more uneven with older milk than fresh milk. Oat drinks foamed more, and the foams were more stable in all samples compared to milks of same age. The effect of foaming temperature was less meaningful with oat drinks than with milks. The sensory properties of milk did not change significantly during the study. The biggest change was the decline of cooked flavor in samples tasted as milk. The same decline was not detected when the milks were tasted as cappuccino drinks. An increase of bitterness was detected in the cappuccinos made by a barista when the milk was 6 months old. According to these results the shelf life of barista milk can be lengthened from 4 months to 5 months.

Lactobacillus rhamnosus GG is a lactic acid bacterium that is widely used as probiotic products in the dairy industry. To gain insights into the genome stability of the L. rhamnosus GG in the human gastrointestinal tract and the possible adaption mechanism under different stresses, we first examined the genotype and phenotype of the L. rhamnosus GG grown over 1000 generations under various stresses, including bile salts, osmotic stress or shearing forces. Immunoblotting analysis of L. rhamnosus grown over 1000 generations showed that the production of mucus-binding pili by L. rhamnosus GG was the most impaired when exposed to bile salts. Complementary PCR screening of 13 highly variable chromosomal regions in GG confirmed that the pilus gene cluster had been lost when exposed to bile stress over time. In vitro bile-induced genomic changes observed in GG possibly reflects the genome plasticity and stability of GG in the human intestinal tract. Still, we showed that these changes only occurred after more than 100 generations, a period of time relatively long compared to the observed time of persistence and transit of GG in the intestinal tract. Although damages and stresses may be caused by bile salts, L. rhamnosus GG still has the ability to tolerate bile salts. The resistance mechanism is still unclear but, based on previous studies, we identified one ABC transporter encoded by the gene operon called tauABC that may be involved in bile resistance. In an effort to demonstrate its function, a tauB-null mutant derivative was generated and phenotypically characterized in terms of metabolic, signaling and functional properties. The data revealed that the tauB-null mutant significantly grow slower than L. rhamnosus GG wild-type strain in the presence of ox bile extracts. Additional screenings using various bile conjugates specifically revealed that two compounds of bile salts, i.e. taurodeoxycholic and taurochenodeoxycholic acid, may be processed by the TauABC transporter, contributing at least partially to the tolerance of GG to bile salts. Overall, we showed that bile salts constitute an important stress factor for GG that causes genomic alterations, although it has bile tolerance mechanisms to bile, such as the newly-characterized tauABC operon.

Gas permeabilities of films used in food packaging must be well known to ensure the best conditions for packed food products. In addition to oxygen and carbon dioxide permeability as such their ratio affects the choice of packaging materials. The CO2/O2 ratio of petroleum derived plastics is normally under 6:1 but that of bio-based films is less known. The literature review of this study focused on different sources of bio-based raw-materials and their chemical structure. The aim of the experimental study was to measure oxygen and carbon dioxide permeabilities of different bio-based films and to identify the CO2/O2 ratio. Another point of interest was the realiability of used carbon dioxide permeation analyzer which was assembled from an old oxygen permeation analyzer and gas chromatography. Three of the used film types were prepared in laboratory scale from Konjac glucomannan, starch and hydroxypropyl starch with 10 % or 40 % of sorbitol (of the dry matter) due to a reduction of porosity of materials. Other bio-based films were obtained from VTT (cellulose nanofibrils, hydroxypropyl xylan, cellulose derivative, cellophane and polyglycolic acid). Almost all the films had low oxygen permeabilities (OP<2.8 [cm3 µm]/[m2 d kPa]) and replicate results did not vary much. The cellulose derivative films had higher OP of 120 (cm3 µm)/(m2 d kPa). The carbon dioxide permeabilities showed more variation and were clearly higher (CO2P was 0 to 978 [cm3 µm]/[m2 d kPa]). In addition films including 40 % of sorbitol leaked more often. The ratio of CO2/O2 varied between 7:1–329:1. Most of the measured bio-based films are suitable for packaging food products, whose preservation depends on the permeability of carbon dioxide through the packaging more than that of oxygen. Excellent applications can be found among fruits and vegetables, whose maturing have to be controlled during storage. High CO2/O2 ratios were due to rather different chemical structures of the studied bio-based films and therefore the determination of a definite CO2/O2 ratio was not possible (unlike with petroleum based films). The magnitude of carbon dioxide permeabilities were similar to those reported in literature but further research with the assembled analyzer is needed to ensure its realiability.

Recently, a new muscular disorder has been reported in chicken M. pectoralis major called Wooden Breast that might be linked to intensive growth selection. The purpose of this study was to find the influence of Wooden Breast condition on protein composition of the breast muscle with special emphasis on myofibrillar and sarcoplasmic protein fractions. For fulfilling the aims of the study, a total number of 34 pectoralis major muscles from both Wooden Breast and normal chickens (Ross 508, Aviagen Ltd, Scotland) were used to evaluate protein composition, protein profile of sarcoplasmic and myofibrillar proteins and their changes, by doing one-dimensional SDS-PAGE analysis. M. Pectoralis major defected by Wooden Breast demonstrated significant decline in sarcoplasmic (P?0.001) and myofibrillar (P?0.05) protein content, in comparison with normal breast muscles. Furthermore, gel electrophoresis indicated significant changes in the intensity of 18 sarcoplasmic protein bands and 7 myofibrillar protein bands. Majority of affected sarcoplasmic proteins were glycolytic enzymes. Moreover, impacted myofibrillar proteins play a role in muscle fibre integrity (e.g. desmin) or calcium signalling. Results of the present study also revealed desmin overexpression with coexistence of a desmin fragment in Wooden Breast which was confirmed by Western-blot technique. In conclusion, the findings of this study indicated defected chicken breast with Wooden Breast contained less protein and the composition differed compared to normal chicken breast muscle, which proves the influence of Wooden Breast condition on protein characteristics of chicken breast muscle. Further studies are needed to interpret the protein changes in the Wooden Breast and the possible role of these changes on metabolic and structural status of the muscle.

The literature part of the study reviewed the recommended gluten quantification method, immunological ELISA R5. R5 is a monoclonal antibody that recognizes mainly the epitope that is abundant in especially gluten protein subgroup, ω-gliadin. The current PWG-gliadin reference material used in ELISA leads to inaccuracy of the gluten content, because it cannot represent sample materials that differ in their gliadin composition. The aim of the experimental study was to compare the prolamin compositions of different wheat cultivars and their reactivity against R5 antibody in sandwich ELISA. The aim was to find the most suitable ratio of barley prolamin, C-hordein, to be used as a reference material for wheat gluten quantification. The ω-gliadin proportions of different cultivars were calculated from RP-HPLC-chromatograms. In order to compare the total wheat gluten reactivity of the cultivars in ELISA R5 with gliadin standard and C-hordein in different ratios (10, 20 and 30% in BSA), Km-values that measure the rate of sensitivity in the assay, were calculated. The method to separate gliadin- and glutenin subgroups in RP-HPLC was optimized (solvent to extract gliadin and glutenin, temperature, injection volume, gradient). For cv. Crusoe the ω-, α/β- and γ-gliadins and HMW- and LMW-glutenins were identified. The selected wheat cultivars were categorized into four groups. The proportion of ω-gliadin in total gliadin ranged from 0.8 to 14.1% between the cultivars, whereas for PWG-gliadin this has been reported to be 7.7%. In terms of similar reactivity (Km-value) in ELISA, 20% C-hordein was found to be the most suitable reference material (Km 90) for the selected wheat cultivars (Km average 92), instead of the current gliadin standard (Km 68). The advantage of C-hordein standard is that the concentration and thus reactivity can be adjusted to match the sample materials with different prolamin profiles. Unlike with current gliadin reference material, it can be used without any conversion factors, which improves the method accuracy.

The literature review of this thesis focuses on cooking loss and factors effecting it as well as low-temperature long-time (LTLT) cooking and how it effects meat. Reactions in meat during heating and their effects on meat products quality were also studied. The aim of the experimental research was to find the optimal strip size for one sous vide process to optimize cooking yield and sensory quality. To do so, pre-testing with several different strip sizes were performed and then one strip size was selected. With this strip size tests with 3 different meat types (chicken, pork and beef) were executed. The tests comprised 10 batches of around 100 kg of meat each type and both strip sizes totaling 60 batches with total weight around 7600 kg. The sensory evaluation was made with a panel of 15 workers from the company to determine if any changes occurred regarding the sensory quality. Every meat type was tasted and evaluated using a scale with a free line segment of 10 cm. The results were measured and the difference between the same type of samples were multiplied with 10 to achieve a difference measured in %-units. Every type of meat had higher cooking yield with larger strip size. Chicken improved the most, pork second and beef the least. The effects on sensory quality were moderate. Chicken and beef became less tender and pork improved, while juiciness of every type improved with bigger strip size. Chicken improved 31.9 %-units, pork 9.8 %-units and beef 6.7 %-units in cooking yield. Chicken overall acceptance seemed to have improved 0.3 %, pork 7.0 % and beef 1.7 % according the sensory evaluation.

Tutkielman kirjallisuuskatsauksessa perehdyttiin aromien herättämiin mielikuviin ja tunteita analysoiviin tutkimuksiin. Lisäksi selvitettiin, onko aromeilla vaikutusta stressiin tai työmuistiin, ja millaisilla menetelmillä niitä on tutkittu. Tutkimuksen tavoitteena oli selvittää, onko aistinvaraisella, verbaalisella kyselyllä ja valokuvilla mahdollista analysoida elintarvikearomien herättämiä mielikuvia ja tunnetiloja. Tutkimus tehtiin Fazerin kanssa yhteistyössä ja se koostui kahdesta kuluttajatutkimuksesta: aromitutkimuksesta (n = 116 henkilöä) ja viinikumimakeistutkimuksesta (n = 85 henkilöä). Aromeina käytettiin yksittäisiä elintarvikearomeja ja kahden elintarvikearomin sekoituksia. Ne valittiin sillä oletuksella, että osa herättäisi energisoivia (cola, inkivääri-appelsiini ja vesimeloni-greippi) ja osa rauhoittavia (vihreä tee, seljankukka-manteli ja hunaja-mansikka) assosiaatioita. Viinikumimakeistutkimuksessa näytemäärä vähennettiin neljään miellyttävimpään elintarvikearomiin: colaan, inkivääri-appelsiiniin, vesimeloni-greippiin ja hunaja-mansikkaan. Aromien herättämiä mielikuvia ja tunnetiloja tutkittiin kahden monivalintakyselyn (check-all-that-apply, CATA) avulla. Aluksi arvioijat valitsivat 16 energisoivaa ja rauhoittavaa assosiaatiota herättävästä valokuvasta jokaista aromia/makua kuvaavat valokuvat. Seuraavaksi arvioija valitsi 25 sanan aromitutkimuksiin suunnatusta tunnetermistöstä (Universal Emotion and Odor Scale, UniGEOS) kutakin tutkittua aromia/makua kuvaavat sanat. Lisäksi näytteiden miellyttävyys ja tuttuus määritettiin 9-portaisella luokka-asteikolla. Tutkimuksissa tuttuus ja miellyttävyys korreloivat ja aromit arvioitiin keskimäärin miellyttävämmiksi kuin vastaavia aromeita sisältäneet viinikumimakeiset. Aromien herättämille mielikuville valitut kuvat asettuivat suurimmaksi osaksi juuri energisoivien ja rauhoittavien valokuvien kohdalle, poikkeuksena hunaja-mansikka. Molempien tutkimusten kohdalla ennakko-oletukset täyttyivät inkivääri-appelsiinin ja colan tunnetermien arvioinnissa, sillä ne arvioitiin virkistäviksi ja energisoiviksi. Tuloksemme osoittavat, että monivalintakyselyn verbaaliset ja visuaaliset menetelmät ovat kuluttajatutkimuksissa hyödyllisiä aromien mielikuvien ja tunteiden analysoimiseen.

The literature review focused on the characteristics of bread-quality rye and how the composition and functional properties of rye are influenced by genotype and environment. Traditional rye sourdough baking process and main baking quality measurements were reviewed. The aim of this work was to identify baking quality of rye flour with different falling numbers. Another aim was to identify the measurement that best determines the quality of rye flour for sourdough baking and to find enzymes that can be used to improve poor-quality flour. In the experimental study, the baking quality of rye flours with different falling numbers (100, 130, 200, 300) was examined in processes for making sourdough rye loaves and serving-size flat breads. Rye flours with high falling numbers (200 and 300) were treated with commercial amylase and xylanase preparations. Falling number, amylograph and swelling curve measurements were done and results were compared to quality obtained in baking trials. Rye flour with the highest falling number (300) resulted in hard and dry dough as well as dense bread, as expected. Other rye flours (100, 130, 200) and flours treated with amylase resulted also in rather hard and dry doughs, although falling number and amylograph measurements confirmed the enzyme activity. Lower falling number and amylase treatments, however, were associated with improved sensory quality of final products. Xylanase made doughs softer and stickier, which improved both handling properties of dough and quality of bread in the loaf process. In contrast, the increased softness and stickiness made the serving-size flat-bread process more difficult. The viscosity decrease caused by xylanase addition was seen in swelling curve measurements. Adjusting the acidity of buffer solution to the pH level of rye sourdough did not improve the ability of the swelling curve to predict the baking behaviour of the flour. This study showed that falling number and amylograph cannot predict properties of rye dough. Differences between rye flours with different falling numbers were best detected in the sensory quality of the final products. The baking quality of rye flours could be modified by enzyme treatments, especially by xylanase addition, but the usefulness and desirability of the treatment depended on the type of bread-making process. The effects of added xylanase in rye dough could be predicted by swelling curve measurement. The overall results emphasized the importance of baking trials in determining the baking quality of rye flour.