Master of Science / Department of Grain Science and Industry / J.M. Faubion / The market for frozen goods is expanding and the frozen dough goods sector still has potential to expand its market. It is well known that deterioration in bread quality occurs during frozen dough/bread production. In addition, it is known that dough rheology influences bread quality. To prevent deterioration of bread quality, many additives have been used and researched. Combinations of oxidants (potassium bromate and ascorbic acid) are widely used worldwide. However, potassium bromate may be carcinogenic to humans, and it has been detected in bread after baking. Since it has been prohibited or strictly limited in many countries, many researchers have tried to find a replacement. Ascorbic acid is safe for human intake, and does not persist in bread. However, it is not as effective as potassium bromate. Possible replacements in frozen doughs include oxidant (ascorbic acid)-enzyme combinations. This study evaluated the effects of ascorbic acid-specific enzyme combinations as a replacement for the potassium bromate in frozen dough and related the effects to dough behavior (gluten network strength) as evaluated by dynamic oscillation rheometry. Bread quality was evaluated by test baking. Based on the results from fresh baking studies, potassium bromate can be replaced by an optimum level combination of ascorbic acid and hemicellulase/endo-xylanase. This combination clearly improved loaf volume, and crumb grain over both control and potassium bromate containing doughs. For frozen dough/bread production, the addition of all additives improved bread quality, but ascorbic acid and endo-xylanase containing dough resulted in higher volume, and better crumb structure than did dough containing potassium bromate. Dough rheology experiments show that rheology was affected by both the process and additives. Strain sweeps gave the information about dough stability. Both the additives and proofing improved dough stability. Dough behavior (gluten network strength) was assessed by frequency sweeps. Dough containing ascorbic acid and endoxylanase was most stable during frozen dough processing.

Author also know as S M Loveday / Fresh bakery products have a very short shelf life, which limits the extent to which manufacturing can be centralised. Frozen doughs are relatively stable and can be manufactured in large volumes, distributed and baked on-demand at the point of sale or consumption. With appropriate formulation and processing a shelf life of several months can be achieved.Shelf life is limited by a decline in proofing rate after thawing, which is attributed to a) the dough losing its ability to retain gas and b) insufficient gas production, i.e. yeast activity. The loss of shelf life is accelerated by delays between mixing and freezing, which allow yeast cells the chance to ferment carbohydrates.This work examined the reasons for insufficient gas production after thawing frozen dough and the effect of pre-freezing fermentation on shelf life. Literature data on yeast metabolite dynamics in fermenting dough were incomplete. In particular there were few data on the accumulation of ethanol, a major fermentation end product which can be injurious to yeast.Doughs were prepared in a domestic breadmaker using compressed yeast from a local manufacturer and analysed for glucose, fructose, sucrose, maltose and ethanol. Gas production after thawing declined within 48 hours of frozen storage. This was accelerated by 30 or 90 minutes of fermentation at 30;C prior to freezing.Sucrose was rapidly hydrolysed and yeast consumed glucose in preference to fructose. Maltose was not consumed while other sugars remained. Ethanol, accumulated from consumption of glucose and fructose, was produced in approximately equal amounts to CO2, indicating that yeast cells metabolised reductively.Glucose uptake in fermenting dough followed simple hyperbolic kinetics and fructose uptake was competitively inhibited by glucose. Mathematical modelling indicated that diffusion of sugars and ethanol in dough occurred quickly enough to eliminate solute gradients brought about by yeast metabolism.

Author also know as S M Loveday / Fresh bakery products have a very short shelf life, which limits the extent to which manufacturing can be centralised. Frozen doughs are relatively stable and can be manufactured in large volumes, distributed and baked on-demand at the point of sale or consumption. With appropriate formulation and processing a shelf life of several months can be achieved.Shelf life is limited by a decline in proofing rate after thawing, which is attributed to a) the dough losing its ability to retain gas and b) insufficient gas production, i.e. yeast activity. The loss of shelf life is accelerated by delays between mixing and freezing, which allow yeast cells the chance to ferment carbohydrates.This work examined the reasons for insufficient gas production after thawing frozen dough and the effect of pre-freezing fermentation on shelf life. Literature data on yeast metabolite dynamics in fermenting dough were incomplete. In particular there were few data on the accumulation of ethanol, a major fermentation end product which can be injurious to yeast.Doughs were prepared in a domestic breadmaker using compressed yeast from a local manufacturer and analysed for glucose, fructose, sucrose, maltose and ethanol. Gas production after thawing declined within 48 hours of frozen storage. This was accelerated by 30 or 90 minutes of fermentation at 30;C prior to freezing.Sucrose was rapidly hydrolysed and yeast consumed glucose in preference to fructose. Maltose was not consumed while other sugars remained. Ethanol, accumulated from consumption of glucose and fructose, was produced in approximately equal amounts to CO2, indicating that yeast cells metabolised reductively.Glucose uptake in fermenting dough followed simple hyperbolic kinetics and fructose uptake was competitively inhibited by glucose. Mathematical modelling indicated that diffusion of sugars and ethanol in dough occurred quickly enough to eliminate solute gradients brought about by yeast metabolism.

No description available.

<p>Савремено пекарство у нашој земљи, још увек, у највећој мери подразумева производњу хлеба и пекарских производа<em> in situ</em>. Припрема пекарских производа у кућним условима своди се, готово искључиво, на мешење према традиционалном<br />моделу. Овакво понашање пекара и потрошача делимично је последица навика, али и изузетно лоше снабдевености нашег тржишта замрзнутим пекарским производима добијеним од квасног теста, као и сировинама намењеним за<br />производњу истих.</p><p>Циљ истраживања обухваћених докторском дисертацијом усмерен је ка дефинисању и унапређењу услова производње и финализације замрзнутих пекарских производа непосредно пред употребу, у близини корисника или од стране самог корисника. Добијени резултати требало би да дају допринос бољем разумевању феномена који се дешавају у поступкузамрзавања/одмрзавања теста. Модификација постојеће, код нас примењиване технологије, у смислу примене одабраних сојева квасца, одабраног режима замрзавања/одмрзавања и дужине чувања теста у замрзнутом стању, као и примене одабраних додатака тесту, требало би да резултује пекарским производима добијеним од замрзаваног теста чије су технолошке и сензорне карактеристике побољшане.</p><p>Испитан је сировински састав теста и квалитет употребљених сировина карактеристичан за наше поднебље са аспекта њихове примене у производњи замрзаваног теста, о чему нема публикованих резултата. Доказана је могућност употребе комерцијалног пекарског квасца и комерцијалног брашна које по садржају и квалитету глутена не одговара у потпуности литературним препорукама.</p><p>Предложене су математичке релације које омогућавају предвиђање трајања операција замрзавања и одмрзавања квасног теста у дефинисаним условима који су уобичајени у пекарској производњи, о чему нема литературних података.<br />Дефинисани су оптимални услови замрзавања и одмрзавања квасног теста који омогућавају очување активности квасца у замрзаваном тесту на прихватљивом нивоу.<br />На основу активности квасца у замрзаваном тесту са хидроколоидима, матурографских и екстензограмских показатеља квалитета као и његове микроструктуре доказан је позитиван утицај додатка хидроколоида у замрзавано тесто са аспекта његовог квалитета. Јасно изражене промене микроструктуре замрзнутог теста током његовог складиштења доприносе разумевању феномена који се дешавају у тесту услед његовог замрзавања, одмрзавања и складиштења у замрзнутом стању до 28 дана, као и интеракција између конституента теста и додатих хидроколоида.</p><p>Доказано да је за припрему замрзаваног теста могуће користити сировине чији квалитет није оптималан, али да се тиме<br />значајно скраћује период складиштења у коме не долази до неприхватљиве деградације његовог квалитета са неколико седмица колико препоручује литература, на свега 7 до 14 дана. Квалитет готовог пекарског производа добијеног од замрзаваног теста које се састоји од сировина уобичајено присутних<br />на нашем тржишту, а које је припремљено уз предложене минималне модификације традиционалног начина припреме хлеба, задовољавајући је из угла конзумента.</p> / <p>Savremeno pekarstvo u našoj zemlji, još uvek, u najvećoj meri podrazumeva proizvodnju hleba i pekarskih proizvoda<em> in situ</em>. Priprema pekarskih proizvoda u kućnim uslovima svodi se, gotovo isključivo, na mešenje prema tradicionalnom<br />modelu. Ovakvo ponašanje pekara i potrošača delimično je posledica navika, ali i izuzetno loše snabdevenosti našeg tržišta zamrznutim pekarskim proizvodima dobijenim od kvasnog testa, kao i sirovinama namenjenim za<br />proizvodnju istih.</p><p>Cilj istraživanja obuhvaćenih doktorskom disertacijom usmeren je ka definisanju i unapređenju uslova proizvodnje i finalizacije zamrznutih pekarskih proizvoda neposredno pred upotrebu, u blizini korisnika ili od strane samog korisnika. Dobijeni rezultati trebalo bi da daju doprinos boljem razumevanju fenomena koji se dešavaju u postupkuzamrzavanja/odmrzavanja testa. Modifikacija postojeće, kod nas primenjivane tehnologije, u smislu primene odabranih sojeva kvasca, odabranog režima zamrzavanja/odmrzavanja i dužine čuvanja testa u zamrznutom stanju, kao i primene odabranih dodataka testu, trebalo bi da rezultuje pekarskim proizvodima dobijenim od zamrzavanog testa čije su tehnološke i senzorne karakteristike poboljšane.</p><p>Ispitan je sirovinski sastav testa i kvalitet upotrebljenih sirovina karakterističan za naše podneblje sa aspekta njihove primene u proizvodnji zamrzavanog testa, o čemu nema publikovanih rezultata. Dokazana je mogućnost upotrebe komercijalnog pekarskog kvasca i komercijalnog brašna koje po sadržaju i kvalitetu glutena ne odgovara u potpunosti literaturnim preporukama.</p><p>Predložene su matematičke relacije koje omogućavaju predviđanje trajanja operacija zamrzavanja i odmrzavanja kvasnog testa u definisanim uslovima koji su uobičajeni u pekarskoj proizvodnji, o čemu nema literaturnih podataka.<br />Definisani su optimalni uslovi zamrzavanja i odmrzavanja kvasnog testa koji omogućavaju očuvanje aktivnosti kvasca u zamrzavanom testu na prihvatljivom nivou.<br />Na osnovu aktivnosti kvasca u zamrzavanom testu sa hidrokoloidima, maturografskih i ekstenzogramskih pokazatelja kvaliteta kao i njegove mikrostrukture dokazan je pozitivan uticaj dodatka hidrokoloida u zamrzavano testo sa aspekta njegovog kvaliteta. Jasno izražene promene mikrostrukture zamrznutog testa tokom njegovog skladištenja doprinose razumevanju fenomena koji se dešavaju u testu usled njegovog zamrzavanja, odmrzavanja i skladištenja u zamrznutom stanju do 28 dana, kao i interakcija između konstituenta testa i dodatih hidrokoloida.</p><p>Dokazano da je za pripremu zamrzavanog testa moguće koristiti sirovine čiji kvalitet nije optimalan, ali da se time<br />značajno skraćuje period skladištenja u kome ne dolazi do neprihvatljive degradacije njegovog kvaliteta sa nekoliko sedmica koliko preporučuje literatura, na svega 7 do 14 dana. Kvalitet gotovog pekarskog proizvoda dobijenog od zamrzavanog testa koje se sastoji od sirovina uobičajeno prisutnih<br />na našem tržištu, a koje je pripremljeno uz predložene minimalne modifikacije tradicionalnog načina pripreme hleba, zadovoljavajući je iz ugla konzumenta.</p> / <p>Currently the baker&#39;s industry in our country is based on the production of bread and bakery products <em>in situ</em>. ln domestic conditions the preparation of bakery products is done solely using the traditional model. This is a consequence of baker and consumer habit in our country as well as the poor market supplies of frozen bakery products from yeast dough and raw material for this production.<br />The aim of research for this dissertation is based on the definition and improvement of the production conditions as well as the flnalization of frozen bakery products prior to use. The results should contribute to the understanding of phenomena that exist in the process of freezing/thawing of dough. In order to preserve the technology commonly<br />used in our country, minor modifications were made using selected yeast types, selected regime of freezing/tharving, frozen dough storage time and additives to dough. These minor changes should result in the improvement of technological and sensor characteristics for baker products obtained from frozen dough. The raw material structure in dough and the quality of used raw material were analyzed from the aspect of the frozen dough production where there is nothing published upon this subject yet. The possibility of the use of commercial baker yeast and flour was proven even though their content and quality of gluten does not correspond to the literature recommendation.<br />Mathematical relations that enable prediction of freezing/thawing of yeast dough operation durance in defined conditions were suggested and has no published results upon this subject yet. Optimal conditions of freezing/thawing yeast dough that preserves the activity of yeast in frozen dough on an accepted level were defined.<br />On the basis of the yeast activity in frozen dough with hydrocolloids, the rheological characteristics and its microstructure, the positive affect of hydrocolloid addition to frozen dough was proven from its quality aspect. Major changes in microstructure of frozen dough during its storage contribute to the understanding of the phenomena that<br />appear in dough during freezing, thawing and storage in frozen state up to 28 days, as well as the interaction between the dough constituents and added hydrocollcids.<br />The possibility of the use of raw material for the dough preparation that has not the optimal quality but shortens the storage time was proven. During this storage time the degradation of its quality does not appear as reconlmended by literature in the period of few weeks but in the period of 7 to 14 days.<br />From the consumerrs point of view the quality of finished bakery product derived from frozen dough with available raw material and with minor modifications of the traditional method of preparation was satisfactorily.</p>