Volatile organic compounds and their generation in sourdough

Received: October 30th, 2022 ; Accepted: April 1st, 2023 ; Published: April 14th, 2023 ; Correspondence: [email protected] technology is involved in bread making process for improving the sensory, rheological, nutritional and shelf life characteristics of bakery products. More than 540 volatile organic compounds (VOCs) and other flavour precursors belonging to the chemical classes, such as aldehydes, ketones, esters, acids, alcohols, terpenes and others, have been identified in sourdoughs and sourdough breads. The synthesis of VOCs is microbial species-specific, originating mainly from fermentation process. VOCs can be used as indicators to characterize microbial processes. Other additional sources of VOCs in sourdoughs are lipid oxidation and browning reactions, the latter of which occurs during the production of dried starter cultures. The purpose of this article is to provide an overview of the composition of VOCs and their effect on the sensory properties of sourdough bread, and to describe the most common extraction methods of VOCs used in the studies of sourdough and bread aroma profile. Long-term propagated sourdough VOCs have been less studied compared to volatiles found in bread crust and crumb or sourdoughs started with defined starter culture(s) due to their complexity and diversity in metabolic pathways, including sophistication of the analytical methodology of VOCs. The relation between sourdough microbiota and its volatile profile is not fully understood and therefore, their variability and precise role as a bread flavour enhancer is not yet known in detail

The Study of Combination of Biodegradable Packaging and Biocoating with Lactic Acid Bacteria as a Green Alternative for Traditional Packaging in Gouda Cheese

Biodegradable packaging, both alone and in combination with acid whey protein coatings, has been used to pack fresh Gouda cheese to improve preservation prior ripening or storage. This study involved three key components: (i) the selection of biodegradable packaging (BP), (ii) the development of a plain liquid acid whey protein concentrate, pectin-based edible coating (BP + Ch + Coating), and (iii) the incorporation of at least 6 log10 CFU (colony forming units) mL−1 Lacticaseibacillus paracasei (BP + Ch + Coating + Lp) and Lactobacillus helveticus (BP + Ch + Coating + Lh) strains. The created compositions were compared with cheese packed in conventional polyethylene (PE) packaging to evaluate their overall synergy effect in reducing microbiological spoilage and influencing chemical parameters in Gouda cheese during 45 days of ripening and cold storage. The evaluation included microbiological analysis (total LAB, Enterobacteriaceae spp., and fungi CFU) and quality assessment of pH, moisture content, water activity, texture, and colour (CEI system) during ripening and shelf life. Although biodegradable packaging (BP) alone did not protect the cheese effectively compared to conventional packaging (EVA/PE/EPC/PVDC), the combination of biodegradable packaging with a coating (BP + Ch + Coating) showed protective properties against Enterobacteriaceae spp. and mould, maintaining moisture, pH, and colour during ripening and storage. Incorporation of L. helveticus (BP + Ch + Coating + Lh) into the coating efficiently decreased the growth of fungi.publishedVersio

Application of Edible Coating Based on Liquid Acid Whey Protein Concentrate with Indigenous Lactobacillus helveticus for Acid-Curd Cheese Quality Improvement

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Screening for Antifungal Indigenous Lactobacilli Strains Isolated from Local Fermented Milk for Developing Bioprotective Fermentates and Coatings Based on Acid Whey Protein Concentrate for Fresh Cheese Quality Maintenance

The demand for healthy foods without artificial food additives is constantly increasing. Hence, natural food preservation methods using bioprotective cultures could be an alternative to chemical preservatives. Thus, the main purpose of this work was to screen the indigenous lactobacilli isolated from fermented cow milk for their safety and antifungal activity to select the safe strain with the strongest fungicidal properties for the development of bioprotective acid whey protein concentrate (AWPC) based fermentates and their coatings intended for fresh cheese quality maintenance. Therefore, 12 lactobacilli strains were isolated and identified from raw fermented cow milk as protective cultures. The safety of the stains was determined by applying antibiotic susceptibility, haemolytic and enzymatic evaluation. Only one strain, Lacticaseibacillus paracasei A11, met all safety requirements and demonstrated a broad spectrum of antifungal activity in vitro. The strain was cultivated in AWPC for 48 h and grew well (biomass yield 8 log10 cfu mL−1). L. paracasei A11 AWPC fermentate was used as a vehicle for protective culture in the development of pectin-AWPC-based edible coating. Both the fermentate and coating were tested for their antimicrobial properties on fresh acid-curd cheese. Coating with L. paracasei A11 strain reduced yeast and mould counts by 1.0–1.5 log10 cfu mL−1 (p ≤ 0.001) during cheese storage (14 days), simultaneously preserving its flavour and prolonging the shelf life for six days.Screening for Antifungal Indigenous Lactobacilli Strains Isolated from Local Fermented Milk for Developing Bioprotective Fermentates and Coatings Based on Acid Whey Protein Concentrate for Fresh Cheese Quality MaintenancepublishedVersio

The determination of the fatty acid composition of bovine colostrum by gas chromatography

Magistritöö eesmärgiks oli uurida eesti punase karja veiste ternespiima rasvhappelise koostise muutuste dünaamikat triatsüülglütseroolides nelja poegimisjärgse lüpsi jooksul. Selleks uuriti kaheksateistkümne Eesti Maaülikooli Märja katsefarmi punast tõugu veiste 1.-4. lüpsikorra ternespiimasid (71 proovi). Ternespiima triatsüülglütseroolide rasvhappelise koostise määramiseks sulatati külmutatud ternespiimaproovid. Rasva ekstraheerimine viidi läbi modifitseeritud Folch’i protseduuriga, kasutades ekstraheerimisel diklorometaani:metanooli lahust (2:1, vol/vol). Gaaskromatograafilised analüüsid teostati rasvhapete metüülestrite analüüsimisel gaaskromatograafiga Agilent 7890A (kapillaarkolonn HP-88: 100 m x 0,25 mm x 0,25 μm). Igast analüüsitud proovist identifitseeriti vähemalt 32 rasvhapet. Proovides enam leidunud rasvhapete sisaldused olid sarnased kirjanduse uuringu käigus leitud andmetega. Samas täheldati varieeruvust üksikisendite, lüpsikorra ning laktatsiooninumbri vahel. Katsetulemuste põhjal leiti, et laktatsiooninumber mõjutab kõikide rasvhapete klasside sisaldust. Erinevate rasvhapete klasside sisalduse uurimisel ilmnes, et küllastunud rasvhapete sisaldus on ternespiimas madalam kui tavapiimas. Küllastunud rasvhapete kontsentratsioon ei tõusnud 48 h möödumisel poegimisest. Nimetatud perioodil püsis küllastunud rasvhapete sisaldus stabiilsena või langes järk-järgult lüpside lõikes. Küllastunud rasvhapete kontsentratsioon oli mõjutatud palmitiin-, müristiin- ja steariinhappe sisaldusest. Nimetatud rasvhapete suurt varieeruvust võib seostada farmispetsiifiliste teguritega, nt. söötmis- ja pidamistingimustega ning keharasva mobilisatsiooniga. Lähtudes, et ligikaudu 50% C16:0 rasvhapetest ja kõik ≥ C18:0 rasvhapped on pärit söötadest või kudede varurasvadest. Küllastunud rasvhapete sisalduse alanemisega kaasnes küllastumata, s.o. monoküllastumata, rasvhapete kontsentratsiooni suurenemine ternespiimas. Monoküllastumata rasvhapete sisalduse varieeruvus erinevate loomade ja lüpside lõikes oli mõjutatud C18:1n9, C16:1n9 ja C14:1n5 sisaldusest, mis olid peamiseid monoküllastumata rasvhappeid ternespiimas. Ternespiim sisaldas 24 h ja 48 h möödumisel poegimisest monoküllastumata rasvhappeid vastavalt 22,65% ja 25,83%, mis on mõnevõrra madalam kirjanduses avaldatuga. Erinevused, mis esinevad kirjandusandmetega, võivad tuleneda tõust, söötmis- ja pidamistingimustest ning esma- ja mitmekordselt poegijate arvust valimis. Võrreldes monoküllastumata rasvhapetega oli polüküllastamata rasvhapete sisaldus oluliselt madalam. Polüküllastumata rasvhapete madalamat kontsentratsiooni võib seostada lipiidide ulatusliku biohüdrogenatsiooniga vatsas. Keskmiselt ligikaudu 1,9% rasvhapetest ternespiimas olid trans-rasvhapped ühe või kahe trans-kaksiksidemega. Peamine trans-18:1 isomeer oli trans-18:1n9 (t9), mille sisaldus varieerus 1. lüpsi ternespiimades vahemikus 0,48-1,48%. Trans-rasvhapete sisaldus oli kõige madalam 1. lüpsikorra proovides. Järgnevate lüpside ternespiimades leiab aset järk-järguline kasv. Äärmiselt suur varieeruvus trans-isomeeride sisalduses on seletatav eelkõige muutuva trans-10 ja trans-11 asendiisomeeride kontsentratsiooniga. Üksikute rasvhapete identifitseerimisel ternespiimaproovidest ilmnes, et 32 rasvhappest 12 rasvhappe sisaldus oli kõrgem kui 1%. Nendeks rasvhapeteks olid või-, kaproon-, kaprüül-, kapriin-, lauriin-, müristiin-, mürist-oleiin-, palmitiin-, palmit-oleiin-, steariin-, oleiin- ja linoolhape. Võrdluseks, tavapiimast tuvastatud 400 rasvhappest on identifitseeritud 15 rasvhappe kontsentratsioon kõrgem kui 1%. Magistritöö teiseks eesmärgiks oli hinnata AOAC 969.33 metoodika sobivust ternespiima rasvhappelise koostise määramiseks. Metoodika katsete läbiviimisel kasutati Märja katsefarmi holsteini-friisi tõugu veiste 1.-4. lüpsikorra ternespiimasid (39 proovi). Metoodika hõlmas endas rasva ekstraheerimist ja derivatsioon, mille käigus rasvhapped esterfitseeriti happelise katalüsaatoriga boor trifluoriid (BF3). Saadud rasvhapete metüülestreid analüüsiti gaaskromatograafiga Varian 3900 (kapillaarkolonn DB-FFAP: 30 m x 0,53 mm x 0,50 μm). Mõõtmistulemuste kokkulangevust hinnati kirjandusandmete ja EPK tõugu veiste ternespiima rasvhappelise koostise analüüsimisel saadud tulemustega. Metoodika katsetulemustest ilmnes, et rasvhapete metüülestrite lahutamisefektiivsus on mõjutatud lisaks analüütide keemistäppidele ja molaarmassidele ka kolonni pikkusest ja statsionaarse faasi polaarsusest. Kapillaarkolonn DB-FFP sobib lühikese ja keskmise ahelaga rasvhapete lahutamiseks, kuid mitte rasvhapete isomeeride (cis-trans) lahutamiseks. Retentsiooniaegade alusel identifitseeriti kümne rasvhappe olemasolu ja kontsentratsioon analüüsitud proovides. Nendeks rasvhapeteks olid C8:0, C10:0, C12:0, C14:0, C14:1n5; C16:0, C16:1n9, C18:0, C18:1n9 (c+t) ning C18:2n6 (c+t). Metoodika katsetulemuste võrdlemisel ilmnes hea kokkulangevus kirjandusandmetega rasvhapete C8:0, C12:0, C14:0, C14:1n5, C16:0 ja C18:1n9 (c+t) suhtes. Ülejäänud rasvhapete sisalduses esines suuremaid erinevusi, mis võisid tuleneda loomade individuaalsetest iseärasustest, söötmis- ja pidamistingimustest, tõust, laktatsiooninumbrist jne. Lisaks võis rasvahapete cis-trans summa olla mõjutatud kolonni lahutamisefektiivsusest. Enamike tulemuste väga hea kokkulangevuse tõttu kirjandusega võib väita, et AOAC 969.33 metoodika sobib ternespiima rasvhappelise koostise uurimiseks.Bovine colostrum consists fat in considerable concentration. Despite the fact, that fat is important for its nutritional value and also for its role in protecting new-born calf against microbial infections, only a few studies have focused on the triacylglycerols (TAGs) composition of colostrum, which is rather different from extensively studied normal milk fat TAGs. The physical properties of milk fat are dependent on the chemical composition and structure of fatty acids present in the constitution of TAGs. Therefore, the efficiency of the separation processes applied to processing of colostrum is directly dependent on its fatty acid composition. The fatty acid composition has also important effects on the taste, consistency and preservation of the fat-rich colostrum products. The objective of the master thesis was to investigate the dynamics of the fatty acid composition in Estonian Red cattle colostrum TAGs during four postpartum milking. To determine the fatty acid composition of colostrum TAGs, total lipid was extracted from each colostrum sample by a modified Folch (1957) procedure using dichloromethane : methanol (2:1, vol/vol). The fatty acid composition of TAG was assessed on an Agilent 7890A gas chromatograph as fatty acid methyl esters. At least 32 different fatty acids were identified from each analysed sample. The second part of the work was to assess the suitability of the AOAC 969.33 method to study the fatty acid composition of colostrum. The methodology included the separation and derivation of fat, where fatty acids were liberated and esterified in presence of catalyst boron trifluorid. The prepared fatty acid metyl esters were dissolved in heptane and analysed by gas chromatography using Varian 3900 gas chromatograph. The results of the study indicate that fatty acid composition changes during postpartum timeline and also differs between individuals and according to the number of lactation. It turned out that all fatty acid classes are influenced by lactation number. Compared with normal milk fat TAGs, colostrum TAGs contain higher levels of saturated fatty acids like mystiric acid, palmitic acid and lauric acid. In contrast, the levels of butyric acid and stearic acid were found to be increasing significantly after calving. In bovine colostrum the concentration of monounsaturated fatty acids were higher than polyunsaturated fatty acids. The content of monounsaturated fatty acids were quite variable. Most of the unsaturated fatty acids were monoenoic acids, primarly C18:1n9, C16:1n9 and C14:1n5. Also it was noticed that there were no considerable changes in minor compounds such as trans fatty acids, including CLA, during postpartum timeline. About 1.9% of trans fatty acids were with one or two double bounds. The main trans isomer was trans-C18:1n9, which content ranged from 0,48% to 1,48% in the first postpartum milking. The results of the methology verification experiment indicated that AOAC 969.33 is suitable for analyzing the fatty acid composition of colostrum

The influence of different factors affecting the texture of colostrum cake

Töö eksperimentaalses osas uuriti ternespiima kogumisvõimalusi üle 500 lehmaga piimakarjades. Tulemustest selgus, et rohkem kui pooled küsitlusele vastanud farmidest oleksid nõus vasikate söötmisest ülejäävat ternespiima müüma kokkuostjale. Kuid müümisel võib takistuseks osutuda vähese kvaliteetse ternespiima kättesaadavus ning vajalike rahaliste ressurside puudus kogumisvõimaluste loomiseks. Piima kalgenemisomadusi mõjutab pH. Töö käigus mõõdeti ternespiima pH-d lüpside lõikes. Mõõtmistulemustest selgus, et lehmade ternespiimade pH-d võivad varieeruda suures ulatuses. Saadud tulemuste põhjal ei saa kindlalt väita, et erinevate loomade ternespiimal ei võiks olla erinev pH dünaamika, kuna valim oli väike ning varasemalt on ternespiima pH-d vähe uuritud. Seetõttu võiks edaspidi uurida pH-dünaamikat, võttes vaatluse alla nt. haigetelt ja tervetelt loomadelt saadava ternespiima. Ternespiima kvaliteedi määramise tulemused kinnitasid varasemate uurimustööde järeldusi, et väärindamiseks sobib eelkõige esimese ja teise lüpsi ternespiim, sest iga järgneva lüpsiga läheneb Ig sisaldus tavapiima koostisele. Kolmanda kuni kuuenda lüpside ternespiimas täheldati rasva kiiret pinnale tõusu. See võib tuleneda rasvakuulikeste suurusjaotusest ning eelnevast piima külmutamisest. Kuna rasva sisaldus mõjutab kvaliteedi määramisel mõõtmistulemuste täpsust, siis oleks tarvis uurida selle mõju mõõtmistulemustele. Ternespiima viskoossuse uuringutest selgus, et esimese ja teise lüpsi ternespiima viskoossus on märgatavalt kõrgem järgnevatest lüpsidest. See võib olla seletatav kuivainesisalduse erinevusega. Varasemad ternespiima reoloogilised uuringud puuduvad. Seetõttu tuleb edaspidi põhjalikumalt uurida ternespiima reoloogiat erinevate lüpside lõikes. Temperatuuri mõju uurimiseks ternespiimakoogi vadaku sünereesile, kuumtöödeldi ternespiimasid 10 minuti jooksul kolmel erineval temperatuuril: 160 °C, 180 °C ja 200 °C juures. Lisaks uuriti lõikamise ja säilitamise mõju vadaku sünereesile. Katsete tulemusel selgus, et kõrgem temperatuur põhjustab intensiivsema vadaku sünereesi. Hilisemad lõikamised ja säilitamised ei põhjustanud täiendavat vadaku sünereesi (va. 200 °C juures). Edaspidi tuleb uurida lisandite (nt. marjade, puuviljade, maitseainete jne) mõju ternespiima pH-le ja vadaku sünereesile. Kõrgete temperatuuride kasutamine põhjustab bioaktiivsete koostisosade hävimist, mistõttu tuleb väljatöötada alternatiivne meetod ternespiimakoogi valmistamiseks.The aim of this study was to investigate the factors which have an effect on the texture of colostrum cake. The literary part gives an overview of the history of bovine colostrum. Also the composition, quality and factors affecting the quality of colostrum are thoroughly observed. In the experimental part of the study: the possiblities of collecting colostrum from Estonian dairy farms; the pH and the quality of colostrum; the viscosity of colostrum; the relation between milking time and making the colostrum; the dependence of colostrum cake whey syneresis, including parameters like temperature, cutting and preserving; the firmness of colostrum cake were examined. Based on the experiments it appeared that higher cooking temperatures caused more intensive syneresis of whey. The optimal temperature to make the colostrum cake is 160 °C. In addition, from the analysis it turned out that it is possible to measure the quality of the colostrum cake coagulant with texture analyzer. By rheological measurements it is possible to predict the coagulation of colostrum

Genotypic Stability of Lactic Acid Bacteria in Industrial Rye Bread Sourdoughs Assessed by ITS-PCR Analysis

Sourdough bread production relies on metabolically active starters refreshed daily with flour and water. The stability of sourdough microbial strains is crucial for consistent bread quality. However, many bakeries lack information on the persistence of starter cultures in ongoing sourdough production. Consequently, there is growing interest in identifying microbial strains from regularly used sourdoughs that possess good functional properties and resist changes in the complex growth environment. This study aimed to evaluate the composition and stability of lactic acid bacteria (LAB) in industrial wheat (WS) and rye (RS) sourdoughs propagated over a long period. LAB isolates (n = 66) from both sourdoughs, sampled over four seasons, were identified using phenotypic methods and genotyped via ITS-PCR and ITS-PCR/TaqI restriction analysis. Eight LAB species were detected, with Lactiplantibacillus plantarum being the most dominant and stable. Nineteen distinct LAB genotypes were observed, highlighting significant diversity. The presence of identical LAB genotypes in both sourdoughs suggests microbial transfer through the environment and bakery workers. LAB in RS were found to be more stable than those in WS. These findings underscore the importance of monitoring microbial stability and diversity in industrial sourdough production to maintain consistent bread quality

Mapping boundaries: Microprosodic and dialectal variability in the perception of Estonian long and overlong quantity (DATA)

This repository contains the data and code for the paper Lippus, Pärtel, Liis Kask, Sofia Lutter, Nele Põldver, Kairi Kreegipuu. 2025. Mapping boundaries: Microprosodic and dialectal variability in the perception of Estonian long and overlong quantity. – Eesti Rakenduslingvistika Ühingu aastaraamat = Estonian Papers in Applied Linguistics 21. This paper presents the results of a web-based perception experiment that tested the distinction of long (Q2) and overlong (Q2) quantity degrees in Estonian. Firstly, we observe segmental quality effect on the quantity perception. The stimuli were created from words with 8 different segmental combinations. The second aim of this study is to map the dialectal variability in Estonian quantity perception. There has been some evidence that the listeners from East and South dialect areas are less sensitive to pitch cue than those from North and West. The current study was carried out with 290 participants with various regional background. The results showed that different segmental quality sets have slightly different Q2–Q3 category boundaries. Also, the precision of quantity identification was considerably lower in the case of nonsense word set. Unexpectedly, we were not able to find a clear dialectal background effect