Alternative approaches to improve the processing and quality of under-utlized fish

Due to the global issues related to climate change and population growth, more sustainable use of existing food resources is required. Fish and other aquatic organisms are rich in health beneficial polyunsaturated fatty acids, protein, and several vitamins and minerals. Fish and other aquatic resources are estimated to play an even more vital role in the future. While many popular fish stocks have already been overexploited, several species are currently not utilized at all or are directed to low-value, non-human uses, such as feed. One example of such species is Baltic herring (Clupea harengus membras). Baltic herring is the most important commercial capture species in Finland, based on both value and quantity. However, only a small fraction of the total catch is used as food. Some factors limiting the food use of Baltic herring include the decreasing size of the caught fish, its high susceptibility to oxidation and other degradation leading to quality loss, as well as its distinct odor and flavor that are not preferred by some consumers. Roach (Rutilus rutilus) along with other cyprinid fish, are not commercially important fish species, and are utilized for human consumption even less than Baltic herring. In addition to providing a valuable source of proteins, lipids and other nutriens, increasing the capture of roach and other cyprinid fish could result in beneficial effects in reducing eutrophication. This thesis focused on alternative ways of increasing utilization of underutilized fish, with a focus on Baltic herring and roach. The two processing methods studied were the pH shift and enzymatic hydrolysis, both of which have been widely studied for other fish species but not Baltic herring or roach. Both processes have the advantage that whole fish or fish side streams without any pre-processing can be used as raw materials. Further, the addition of natural antioxidants was investigated as a means of inhibiting lipid oxidation and degradation of sensory quality during frozen and refrigerated storage of minced Baltic herring. Lingonberry juice press residue, sea buckthorn juice press residue, sea buckthorn juice press residue after supercritical CO2 extraction of lipids, and a commercial extract mixture as natural additions were compared to conventional antioxidants ethylenediaminetetraacetic acid (EDTA) and combination of α-tocopherol and ascorbic acid. The composition of proteins and lipids in Baltic herring and roach protein isolates and hydrolysates was significantly affected by the processing type (pH shift or enzymatic hydrolysis). Compared to enzymatic hydrolysis, the pH shift led to enrichment of essential amino acids, phospholipids, and in case of acid extraction, also polyunsaturated fatty acids such as docosahexaenoic acid (DHA). The pH shift, especially alkaline pH shift, however, induced considerable lipid and protein oxidation. The fish protein hydrolysates (prepared using enzymatic hydrolysis) showed more moderate formation of hydroperoxides, secondary volatile oxidation products, and protein carbonyls. The incomplete elimination of fishy odors and flavors during preparation of fish protein isolates and hydrolysates is a major factor limiting their use. Based on this research, while not completely eliminating these odors, the alkaline pH shift reduced the total intensity of odor and intensity of the fishy odor in Baltic herring, which was reflected in the quantity and quality of odor-active compounds. The natural antioxidants, lingonberry juice press residue (3%), sea buckthorn juice press residue (3% w/w), and commercial extract mixture (0.1%) retarded lipid oxidation in Baltic herring mince stored at –20 °C more effectively than EDTA or combination of α-tocopherol and ascorbic acid, as indicated by lower loss of polyunsaturated fatty acids, lower PV, and/or lower formation of secondary oxidation related volatiles, such as 1-penten-3-ol and hexanal. During refrigerated storage (1 °C), sea buckthorn juice press residue after supercritical CO2 oil extraction and lingonberry juice press residue were effective antioxidants also at the lower concentrations (1.5%, 1%). Based on the odor and flavor profile of Baltic herring minces, particularly sea buckthorn juice press residue after supercritical oil extraction (1.5%), also prevented changes in sensory quality during a 3-day storage. This was further reflected in the odoractive compounds of raw minces. Berry press residues are side streams of berry juice and oil production, and their use as antioxidantive materials would provide added value for these currently under-utilized materials as well. This thesis provided valuable insights related to increasing utilization of Baltic herring and other under-utilized fish. The results showed that pH-shift processing and enzymatic hydrolysis of Baltic herring and roach produced fish protein isolates and hydrolysates with high nutritional quality. However, lipid and protein oxidation during these processes and storage of Baltic herring poses a challenge for preservation of quality. Use of antioxidants may improve preservation of the nutritional and sensory quality of Baltic herring during processing and storage

Localization of decorin gene expression in normal human breast tissue and in benign and malignant tumors of the human breast

The small extracellular matrix proteoglycan decorin which possesses a potent antitumor activity has been shown to be present in various amounts in the stroma of several tumors including those of the breast. Regarding decorin in breast malignancies the published data are conflicting, i.e., whether breast cancer cells express it or not. Here, we first compared decorin gene expression levels between healthy human breast tissue and selected types of human breast cancer using GeneSapiens databank. Next, we localized decorin mRNA in tissue specimen of normal human breast, intraductal breast papillomas and various histologic types of human breast cancer using in situ hybridization (ISH) with digoxigenin-labeled RNA probes for decorin. We also examined the effect of decorin transduction on the behavior of cultured human breast cancer MCF7 cells. Analysis of GeneSapiens databank revealed that in various human breast cancers decorin expression is significant. However, ISH results clearly demonstrated that human breast cancer cells independently of the type of the cancer do not express decorin mRNA. This was also true for papilloma-forming cells of the human breast. Indeed, decorin gene expression in healthy human breast tissue as well as in benign and malignant tumors of human breast was shown to take place solely in cells of the original stroma. Decorin transduction using decorin adenoviral vector in decorin-negative MCF7 cells resulted in a significant decrease in the proliferation of these cells and changed cell cohesion. Decorin-transduced MCF7 cells also exhibited increased apoptosis. In conclusion, our study shows that in human breast tissue only cells of the original stroma are capable of decorin gene expression. Our study also shows that transduction of decorin in decorin-negative human breast cancer cells markedly modulates the growth pattern of these cells

Effect of supercritical CO2 plant extract and berry press cakes on stability and consumer acceptance of frozen Baltic herring (Clupea harengus membras) mince

A promising way of processing Baltic herring, Clupea harengus membras, is turning the fish into boneless mince. However, Baltic herring is prone to lipid oxidation, which possesses a challenge for industrial applications. The aim of this work was to study the efficacy of press cakes from Finnish berries and a supercritical CO2 plant extract to limit lipid oxidation during frozen storage of Baltic herring mince and to determine the impact of these additions on consumer acceptance in a fish product. Peroxide value, formation of volatile oxidation products and loss of polyunsaturated fatty acids showed that the tested natural additives decreased oxidation to a greater or similar extent as conventional antioxidants during 10-month storage. While potential of berry press cakes and plant extracts as "green label antioxidants" was shown, consumer study indicated need for further research to reach both optimal antioxidative efficacy and sensory properties.Peer reviewe

Comparison of enzymatic and pH shift methods to extract protein from whole Baltic herring (Clupea harengus membras) and roach (Rutilus rutilus)

This study aimed to establish the differences between enzymatically extracted hydrolysates and pH shifted protein isolates from whole Baltic herring and roach in terms of polypeptide patterns, functionality, sensory properties, microbial quality, yield, and composition. Alkaline extraction resulted in the highest yields, whereas the hydrolysates showed the highest protein contents. The hydrolysates showed higher protein solubility (86.0–88.5%) than the protein isolates (5.1–14.5%) as well as the higher foam capacity for Baltic herring. However, for roach, alkaline extracted protein isolates exhibited the highest foam capacity. All hydrolysates showed poor foam stability (0–13%) while the protein isolates showed notably higher stability (30–55%). The hydrolysates showed relatively low bitterness, whereas alkaline extracted roach proteins were perceived as bitter. This study demonstrated that it was possible to produce protein isolates and hydrolysates from whole fish with good microbial quality. However, both processes need to be optimised according to the food application and fish species.</p

Effect of supercritical CO2 plant extract and berry press cakes on stability and consumer acceptance of frozen Baltic herring (Clupea harengus membras) mince

A promising way of processing Baltic herring, Clupea harengus membras, is turning the fish into boneless mince. However, Baltic herring is prone to lipid oxidation, which possesses a challenge for industrial applications. The aim of this work was to study the efficacy of press cakes from Finnish berries and a supercritical CO2 plant extract to limit lipid oxidation during frozen storage of Baltic herring mince and to determine the impact of these additions on consumer acceptance in a fish product. Peroxide value, formation of volatile oxidation products and loss of polyunsaturated fatty acids showed that the tested natural additives decreased oxidation to a greater or similar extent as conventional antioxidants during 10-month storage. While potential of berry press cakes and plant extracts as“green label antioxidants”was shown, consumer study indicated need for further research to reach both optimal antioxidative efficacy and sensory properties</p

Baltic herring (Clupea harengus membras) protein isolate produced using the pH-shift process and its application in food models

In this study, protein isolate was prepared from Baltic herring (Clupea harengus membras) using alkaline pH-shift process. The aim of this research was to characterize the protein isolate and to study its potential in food models. A special focus was placed on characterization of odour profile and volatile compounds contributing to the odour profile of the protein isolate using gas chromatography - olfactometry. 2,3-Pentanedione, hexanal, 4(Z)-heptenal, 2,4(E,E)-nonadienal, and three compounds tentatively identified as 1,5(E)-octadien-3-ol, 1,5(Z)-octadien-3-ol, and 1,5(Z)-octadien-3-one were the most important odour-contributing compounds in the protein isolate (Nasal Impact Factor 83-100%, intensity 2.6-3.3 on a scale 0–4). 2-Methylpropanal, 2- and 3-methylbutanal, and three unknown compounds were less intense in the protein isolate than in the raw material, which might have contributed to the lower intensity of fishiness observed for the protein isolate (2.2 vs 3.3 on a scale 0–4). Surimi-type gels prepared from the Baltic herring protein isolate had texture properties (hardness and cohesiveness) similar to those of commercial products. Due to the abundancy of dark muscle tissue in Baltic herring, the protein isolate had a significantly lower whiteness (W=63) compared to the commercial surimi products (W=80–83). Increasing the solubilisation or precipitation pH did not improve the whiteness, but resulted in significantly softer, less cohesive, and less chewy gels. The findings of this study indicate that alkaline-based pH-shift processing is a potential way to increase the food application of Baltic herring.</p

Quality of Protein Isolates and Hydrolysates from Baltic Herring (Clupea harengus membras) and Roach (Rutilus rutilus) Produced by pH-Shift Processes and Enzymatic Hydrolysis

Fractionation is a potential way to valorize under-utilized fishes, but the quality of the resulting fractions is crucial in terms of their applicability. The aim of this work was to study the quality of protein isolates and hydrolysates extracted from roach (Rutilus rutilus) and Baltic herring (Clupea harengus membras) using either pH shift or enzymatic hydrolysis. The amino acid composition of protein isolates and hydrolysates mostly complied with the nutritional requirements for adults, but protein isolates produced using pH shift showed higher essential to non-essential amino acid ratios compared with enzymatically produced hydrolysates, 0.84-0.85 vs. 0.65-0.70, respectively. Enzymatically produced protein hydrolysates had a lower total lipid content, lower proportion of phospholipids, and exhibited lower degrees of protein and lipid oxidation compared with pH-shift-produced isolates. These findings suggest enzymatic hydrolysis to be more promising from a lipid oxidation perspective while the pH-shift method ranked higher from a nutrient perspective. However, due to the different applications of protein isolates and hydrolysates produced using pH shift or enzymatic hydrolysis, respectively, the further optimization of both studied methods is recommended

Effects of Weak Acids on the Microbiological, Nutritional and Sensory Quality of Baltic Herring (Clupea harengus membras)

Baltic herring (Clupea harengus membras) pickled in vinegar is a common product in the Nordic countries. Other weak acids are used to cook and preserve fish in other food cultures. The aim of this study was to evaluate the potential of weak acids to produce safe and nutritious pickled fish products with varying sensory properties. The influence of acetic, citric, lactic, malic, and tartaric acids on the preservability and quality of pickled and marinated Baltic herring was studied by measuring microbiological quality, pH, chemical composition, and lipid oxidation and by sensory profiling. Pickling with these acids with pH levels of 3.7-4.2 resulted in pickled Baltic herring products with high microbiological quality. The results of the chemical analysis of the samples indicated that pickling and storage on marinade influenced the chemical composition of fish. The most significant changes in chemical composition were the increase in moisture and decrease in protein content of the samples during storage. Fat content decreased during the storage period in acetic acid and malic acid samples. All tested acids inhibited lipid oxidation for one month, but at three and four month time points, the content of oxidation products increased except in the samples pickled with tartaric acid. The highest oxidation level was observed in the case of citric acid and the lowest with tartaric acid. The results indicate that replacing acetic acid with other weak acids frequently used in the food industry results in pickled and marinated fish products with novel and milder sensory profiles

Kaiken takana on laadukas raaka-aine – Silakan laadun mittausmenetelmät

Kalatalouden innovaatio-ohjelma Blue Products keskittyy kotimaisen kalan arvon lisäämiseen kehittämällä alihyödynnettyjen kalojen, kuten silakan ja särkikalojen käyttöä elintarvikkeissa ja uusissa, innovatiivisissa korkean lisäarvon erikoistuotteissa. Kuluttajien kiinnostus silakkaa ja särkikaloja kohtaan ympäristöystävällisenä ja terveellisenä ruokana on viime aikoina kasvanut, mutta toisaalta samaan aikaan yrityskentältä ja kuluttajilta on tullut viestiä silakan laadun vaihtelusta ja liian heikosta säilyvyydestä. Sekä perinteistä ruokakäyttöä että innovatiivisempia tuotteita varten kalan laadun onkin oltava erinomainen. Jotta silakan laatua pystytään parantamaan, pitää laatu pystyä mittaamaan numeerisesti kalastusalukselta kauppaan. Tässä raportissa arvioidaan erilaisten mittausmenetelmien soveltuvuutta silakan laadun määrittämiseksi kalaketjun eri vaiheissa ja tarvetta uusille pikamenetelmille laadun mittaamiseksi.Kuluttajalle laatu näyttäytyy aistittavana laatuna. Kalojen aistinvaraisen laadun tutkimuksessa voidaan käyttää monenlaisia menetelmiä, mutta kalaketjun käyttöön tarvitaan helposti omaksuttava ja mielellään älylaitteessa toimiva yksinkertainen numeerinen mittari. Tällaiseksi voisi soveltua silakalle kehitetty laatuindeksiin perustuva älypuhelinsovellus, joka mukailee ”How fresh is your fish”-sovellusta. Tämän tuomiseksi käytäntöön tarvitaan yhteistyökumppaniksi ohjelmistoyritys. Aistittavan laadun taustatekijät ovat joukko kemiallisia, biokemiallisia, fysikaalisia ja mikrobiologisia ilmiöitä, joiden mittaamiseen löytyy lukuisia menetelmiä. Lupaavilta kalan laadunvalvontaan ja tuoreuden arviointiin prosessoinnissa ja kaupassa vaikuttavat kaupalliset pikamenetelmät kuten ”Freshness checker” ja ”PRECICE® Freshness Assay Kit”, sekä pakattujen tuotteiden kohdalla erilaiset värimuutokseen perustuvat kemosensitiiviset sensorit, jotka viestivät kalan laadusta sekä kuljetuksen että säilytyksen aikana. Kalan sähköisten ominaisuuksien muutoksiin perustuvat Torrymeter sekä Fischtester VI ovat edelleen käyttökelpoisia, kaupallisesti saatavia, koko ketjun seurantaan soveltuvia kalan tuoreusmittareita, mutta ne ovat epäherkkiä ja alttiita erilaisille virhemittauksille. Sähkökemiallinen impedanssispektrosopia (EIS) antaa kalan koostumuksesta tarkempaa informaatiota. Tämän menetelmän mahdollisuuksia silakan laadun mittaamiseen tullaan testaamaan Blue Products -ohjelman jatkotutkimuksissa. Erilaiset kuvantamistekniikat, kuten hyperspektrikuvantaminen, tarjoavat mielenkiintoisia uusia mahdollisuuksia kalan laadun määrittämiseksi ja esimerkiksi kalansaaliin lajitteluun laadun perusteella. Kuvantamistekniikka on vielä nykyisellään melko kallista, mutta toisaalta kuvantamismenetelmät ovat jo vakiinnuttaneet asemansa laajasti teollisuuden eri aloilla ja elintarviketeollisuudessa laaduntarkkailussa.</p

Henkilökunnan säteilyaltistus ja säteilysuojien käyttö koronaariangiografiassa

Koronaariangiografia eli sepelvaltimoiden varjoainekuvaus on ensisijainen tutkimusmenetelmä tutkittaessa potilasta, jolla on suuririskinen sepelvaltimotauti. Suonia kuvataan läpivalaisuavusteisesti käyttäen C-kaarta, jonka toiminta perustuu röntgensäteilyyn. Tutkimusta suoritettaessa henkilökunta on läpivalaisun aikana valvonta-alueella ja altistuu säteilylle. Tutkimuksen tarkoituksena on kuvailla henkilökunnalle aiheutuvaa säteilyaltistusta koronaariangiografiatutkimuksissa ja henkilökunnan säteilysuojainten käyttöä tutkimuksen aikana. Tutkimuksessa saadaan tarkkaa tietoa henkilökunnan säteilyannoksista ja säteilysuojien käytöstä koronaariangiografiassa. Tavoitteena on kehittää henkilökunnan säteilyturvallisuutta ja tutkimustuloksia voidaan hyödyntää uuden kuvantamislaitteen kehittämisessä, henkilökunnan säteilyaltistuksen optimoinnissa sekä turvallisuuskulttuurin kehittämisessä. Tutkimuksessa mitattiin henkilökunnalle aiheutuneita säteilyannoksia Oulun Yliopistollisen sairaalan kardiologisella osastolla. Mittaukset tehtiin käyttäen DoseAware -järjestelmää, jolla voidaan mitata annosnopeutta reaaliaikaisesti, sekä tallentaa annostiedot jokaisesta tutkimuksesta. Mittareita oli käytössä kuusi kappaletta ja ne sijoitettiin kattokiinnitteiseen säteilysuojaan, kardiologin, instrumenttihoitajan ja potilasta tarkkailevan hoitajan lyijysuojien päälle. Tutkimusaineisto koostuu 12 koronaariangiografiatutkimuksesta. Henkilökunnan säteilyannokset olivat pääasiassa pieniä. Suurimmat annokset tulivat kardiologille ja potilasta tarkkailevalle hoitajalle. Kardiologin saamaan annokseen vaikutti merkittävimmin liikuteltavien lyijysuojien oikeaoppinen käyttö ja potilasta tarkkailevan hoitajan annokseen vaikutti hoitajan sijainti salissa läpivalaisua käytettäessä. Tutkimus osoittaa, että oikealla sijoittumisella ja suojien oikealla käytöllä tutkimuksen aikana henkilökunnan säteilyaltistus saadaan hyvin alhaiseksi. Jatkotutkimushaasteena voisi olla henkilökunnan saaman säteilyaltistuksen laajempi mittaaminen käyttäen useampia mittareita.Coronary angiography is a procedure that is performed when examining patients who are at risk for coronary heart disease. Coronary angiography is a method that uses special dye and x-ray. X-ray is produced by using mobile C-arm. Because the personnel are inside the examination room during the examination, personnel are exposed to radiation. The objective of the study was to describe the radiation exposure of the personnel and observe how personnel use radiation protection shields. The aim of the study was to develop radiation safety. Research results can be used for estimating the need of a new heart imaging method, optimizing the radiation exposure of the personnel and developing radiation safety culture. The study was performed in Oulu University Hospital. The radiation doses were measured by using DoseAware measuring system, which shows doses in real time. Six dosemeters were placed on the lead shields of cardiologist, instrumental nurse, the nurse observing the patient and the overhead lead shield. The study included 12 coronary angiography examinations. The study showed that radiation doses of the staff were low, also zero doses were received. Cardiologists and the nurses observing the patient had the highest doses. The most significant factor affecting cardiologists’ radiation doses was using the overhead lead shield correctly. The distance to the source of radiation while using the x-ray affected most the doses of the nurses. The study showed that using the lead shielding correctly and keeping distance to the source of radiation makes it possible to keep radiation doses very low. Further research could be measuring doses more extensively using more dosemeters