Aspetti cinetici delle fermentazioni coinvolte nella produzione del Pane Toscano a lievitazione naturale.

La panificazione ha radici molto antiche: la forma di pane più antica rinvenuta in Europa (Twann, Svizzera) risale al 3530 a.C., ma sono stati gli Egiziani i primi a far lievitare l’impasto utilizzando la lievitazione naturale, ancora oggi utilizzata nella lavorazione di prodotti tipici tradizionali come il Pandoro ed il Panettone, ma anche del pane toscano a lievitazione naturale, un pane bianco, caratterizzato dall’assenza di sale, ottenuto utilizzando come materie prime farina di grano tenero, acqua e lievito naturale. L’impiego del lievito naturale ha riflessi positivi sulla conservabilità, sulla digeribilità, ma anche sulle caratteristiche organolettiche del pane finito, che si manifestano con un sapore ed un aroma peculiari, dovuti alla formazione di sostanze volatili aromatiche, che si formano durante la lievitazione e quindi la cottura. Poiché il conferimento del marchio DOP prevede che siano chiaramente ed univocamente individuate le caratteristiche che legano il prodotto finito al territorio di riferimento (Regione Toscana), non è possibile accettare degli intervalli di variabilità troppo elevati per i parametri che lo caratterizzano. Per assicurare la richiesta riproducibilità, occorre disporre di approfondite informazioni sulla composizione della microflora presente nell’impasto per evidenziare l’esistenza di eventuali correlazioni che la legano ai parametri chimico-fisici e organolettici del pane finito. A questo scopo dovranno essere individuate le relazioni che intercorrono tra le principali variabili tecnologiche (temperature, tempi, composizioni delle materie prime e degli intermedi di processo, pH, concentrazione di etanolo, concentrazione in acido lattico ed acetico, ecc.) e lo sviluppo delle diverse popolazioni microbiologiche, per produrre quegli algoritmi matematici in grado di descrivere l’andamento di questo sistema con i tempi, le temperature e le modalità operative impiegate. Presso tre forni toscani individuati dal Consorzio di promozione e tutela del pane toscano a lievitazione naturale, sono stati, quindi, raccolti campioni della madre acida e dell’impasto a diversi stadi di panificazione per sottoporli ad analisi microbiologica e chimico composizionale al fine di determinare l’evoluzione nel tempo dei principali metaboliti coinvolti nei processi fermentativi (ac. D,L-lattico, ac. acetico ed etanolo). A conferma di quanto riportato in letteratura, la quantità massima di metabolita accumulabile risulta più elevata nei campioni raccolti al centro dell’impasto rispetto a quelli provenienti dalla sua superficie. Infatti, come era facilmente prevedibile, la presenza dell’ossigeno tende ad inibire anche se in modo diversificato, i principali processi fermentativi portando ad una diversa distribuzione dei metaboliti nei campioni analizzati. Anche se le tecnologie e le madri acide utilizzate si diversificano in funzione del forno considerato, le costanti cinetiche connesse all’accumulo dei metaboliti con il tempo di lievitazione non sembrano diversificarsi sostanzialmente. Alla luce dei risultati ottenuti è possibile evidenziare come, adottando la stessa farina suggerita dal Consorzio, il tempo di lievitazione tenda ad annullare rendendole così meno evidenti, le pur notevoli differenze che intercorrono tra le madri a pasta acida utilizzate nei tre forni considerati. Sembrerebbe, quindi, possibile, adottando un'unica madre acida e una tecnologia di panificazione comune, ottenere nel tempo degli impasti sufficientemente simili, anche in forni collocati in zone differenti del territorio regionale e che utilizzano differenti acque di lavorazione

L’UTILIZZO DELLA NEVE CARBONICA NELLA PRODUZIONE DI OLIO EXTRAVERGINE DI OLIVA

Lo scopo del presente lavoro di tesi è l’individuazione di un sistema estrattivo innovativo in grado di valorizzare le caratteristiche nutrizionali ed organolettiche dell’olio vergine di oliva. L’addizione diretta dell’anidride carbonica allo stato solido alle olive prima della frangitura, al fine di promuoverne la criomacerazione, costituisce l’operazione fondamentale che caratterizza questo nuovo sistema di estrazione. L’impiego della neve carbonica come criogeno ha già trovato interessanti applicazioni in campo alimentare in generale e nel settore enologico più in particolare. Infatti, la CO2,s, che a pressione atmosferica tende a sublimare per portarsi in fase aeriforme alla temperatura a -78°C, induce il passaggio dallo stato liquido a quello solido dell’acqua presente all’interno delle cellule delle olive poste direttamente a contatto con questo criogeno. Poiché il volume occupato dalla stessa quantità di acqua allo stato solido risulta superiore a quello inizialmente occupato allo stato liquido, si assisterà ad una perdita della struttura compartimentale cellulare dovuta al così detto crash cellulare, e alla conseguente fuoriuscita dei prodotti in queste contenute facilitandone così la diffusione in fase liquida che si arricchirà in metaboliti cellulari in genere e in olio di estrazione in particolare. La CO2 gassosa, che esibisce un valore di densità superiore a quella dell’aria (densità CO2,g /densità aria = 1.5), tende a permanere al di sopra della pasta di olive in lavorazione, creando così uno strato gassoso inerte in grado di proteggerla dall’ossigeno dell’atmosfera circostante. Diverrebbe così possibile modulare opportunamente non solo i tempi di gramolatura ma anche quelli della sua eventuale esposizione ad una ossigenazione controllata così da poter accumulare all’interno dell’olio estratto i desiderati quantitativi in prodotti ossigenati a valenza aromatica. Una prima consistente parte dell’attività sperimentale connessa a questo lavoro di tesi, è stata dedicata a definire il protocollo sperimentale più idoneo e ad apportare le necessarie modifiche al microfrantoio commerciale utilizzato (Oliomio Baby® -Toscana Enologica Mori), al fine di consentire l’addizione della CO2,s nel corso della lavorazione delle olive. L’addizione di CO2,s appare in grado di migliorare la resa estrattiva (+1%), un valore che appare influenzato da una molteplicità di variabili, tra cui il grado di maturazione raggiunto dalle olive, il loro contenuto in acqua, il tempo e le modalità di conservazione adottate, il rapporto tra peso criogeno/peso olive lavorate. Questo risultato costituisce un evidente e immediato vantaggio commerciale per i produttori, che vedrebbero così accresciuta la loro remunerazione a parità della quantità di olive conferite all’impianto di estrazione. L’innovativa tecnologia estrattiva proposta, consente, inoltre, di ottenere un olio extravergine di oliva più ricco in vitamina E (+6%) e quindi in componenti bioattivi in grado di accrescerne la qualità nutrizionale e ad incrementarne il potere antiossidante e quindi la vita commerciale. Inoltre l’olio estratto operando in presenza del criogeno, tenderebbe ad arricchirsi di quei componenti aromatici tipici della materia prima utilizzata e quindi propri della cultivar di oliva lavorata ma variabili in funzione della zona di produzione e più in particolare delle condizioni pedo-climatiche che ne hanno contraddistinto l’andamento della maturazione nell’annata esaminata. L’olio così prodotto, verrebbe ad essere più strettamente legato alla materia prima utilizzata, alla tipologia di olive lavorate e alla loro zona di produzione, da divenire un prodotto tipico contraddistinto da chiare ed inconfondibili caratteristiche organolettiche facilmente riconoscibile e identificabile dal consumatore che potrebbe divenire disponibile a sostenere un prezzo superiore pur di assicurasi un prodotto qualitativamente più valido

A Mathematical Model to Evaluate the Kinetics of D-glucose and D-fructose Fermentations by Saccharomyces bayanus at Increasing Ethanol Concentration

In the cellar, slow and stuck fermentations occurring during winemaking are often successfully solved by the addition of yeast strains like Saccharomyces bayanus. The kinetic behaviour shown by S. bayanus during alcoholic fermentation was investigated using a mathematical model previously tested for S. cerevisiae, in order to show which of the six functional parameters of the model differed significantly with the yeast population. Although some parameters (hexose fractions converted to ethanol and glycerol) did not change, the kinetic constant related to the inactivation rate of the yeast population showed by S. cerevisiae assumed a value significantly higher (approximately 50-fold) than that observed for S. bayanus, while this latter population was ten times less affected by ethanol than S. cerevisiae. Although no remarkable differences could be found between the ability shown by the two yeast populations to convert hexoses (D-glucose and D-fructose), the tolerance for ethanol accumulation changed strongly. The conversion rate of these two hexoses by S. bayanus was affected less (about ten thousand-fold) by ethanol than that of S. cerevisiae

The influence of packaging on the sensorial evolution of white wine as a function of the operating conditions adopted during storage

With the aim to determine the influence of packaging in preserving the quality of wine, in this research project the sensorial evolution of a white table wine stored in different packaging materials (glass bottles provided with different closures; bag-in-box (BiB) containers; tetrabricks®) and different volumes (2 volumes for each packaging) has been evaluated over a period of 12 months. For each packaging solution two different temperature levels (4° and 20°C) were also maintained throughout the storage period. The preliminary results obtained indicate that wine evolution (characterized by both sensorial and chemical parameters) might be greatly influenced by the packaging characteristics. In particular in glass bottle, the crown cap allowed the best storage conditions for wine, closely followed by natural cork, while the wine maintained in tetrabricks® showed the worst organoleptic profile with the maximum level of oxidation and the highest evolutionary state, closely followed by the wine packaged in BiB containers

Development of phenol-enriched olive oil with phenolic compounds extracted from wastewater produced by physical refining

While in the last few years the use of olive cake and mill wastewater as natural sources of phenolic compounds has been widely considered and several studies have focused on the development of new extraction methods and on the production of functional foods enriched with natural antioxidants, no data has been available on the production of a phenol-enriched refined olive oil with its own phenolic compounds extracted from wastewater produced during physical refining. In this study; we aimed to: (i) verify the effectiveness of a multi-step extraction process to recover the high-added-value phenolic compounds contained in wastewater derived from the preliminary washing degumming step of the physical refining of vegetal oils; (ii) evaluate their potential application for the stabilization of olive oil obtained with refined olive oils; and (iii) evaluate their antioxidant activity in an in vitro model of endothelial cells. The results obtained demonstrate the potential of using the refining wastewater as a source of bioactive compounds to improve the nutraceutical value as well as the antioxidant capacity of commercial olive oils. In the conditions adopted, the phenolic content significantly increased in the prototypes of phenol-enriched olive oils when compared with the control oil

Evaluation of Chemical Composition of Two Linseed Varieties as Sources of Health-Beneficial Substances

Linseed (Linum usitatissimum L.) is becoming more and more important in the health food market as a functional food, since its seeds and oil represent a rich source of bioactive compounds. Its chemical composition is strongly correlated with, and dependent on, genetic characteristics. The aim of this study was to evaluate the variation in seed yield, oil content, fatty acid composition and secondary metabolite profiles between a low-linolenic linseed variety, belonging to the Solin-type group (Solal), and a high-linolenic traditional one (Bethune), cultivated, both as spring crops, in open field conditions of Central Italy. The achieved results pointed out the dierent behavior of the two varieties in terms of growth cycle, oil content, and some important yield components, such as capsule number per plant and thousand seed weight. There were also significant dierences in seed composition regarding total phenols, total flavonoids, antioxidant activities as well as in carotenoid, tocopherol, and tocotrienol profiles between the two varieties. In particular, Solal was characterized by the greatest contents of oil, phenols, flavonoids, - and - tocotrienol, together with the highest antioxidant activity. Bethune, on the contrary, showed the highest amounts of carotenoids (lutein and -carotene). These results indicate a clear eect of the genetic characteristics on the biosynthesis of these secondary metabolites and, consequently, on the related antioxidant activity. Our findings suggest that the mutation process, responsible for the selection of the low-linolenic cultivar, is able to modify the biosynthetic pathways of carotenoids and phenolics

Nutraceutical Oils Produced by Olives and Citrus Peel of Tuscany Varieties as Sources of Functional Ingredients

The essential oils extracted from the peels of two Tuscany Citrus of the Massa province have been characterised. Moreover, the flavedo of these species has been used in the production of two Citrus olive oils (COOs) obtained with an innovative method in which the citrus peels are cryomacerated and then pressed with the olives. The presence of functional compounds, such as carotenoids, naringenin and minor phenolics, classifies these COOs as nutraceuticals with the potential to develop enriched foods able to promote a healthy diet. Moreover, the increased presence of tyrosol and hydroxytyrosol, compared to the unflavoured oil, further highlights the nutritional value to the two COOs, being these phenolic compounds recognized as good possible therapeutic candidates for the inhibition of neurodegenerative diseases as the Parkinson's disease. In this perspective, the citrus peels, rich in bioactive compounds, have been valued transforming their waste nature in an innovative resource

The effects of packaging and storage temperature on the shelf-life of extra virgin olive oil

This research aimed to study the effects of packaging and storage temperature on the shelf-life of an extra virgin olive oil (EVOO) as it can occur in most points of sale. The evolution of the chemical and sensory characteristics of an EVOO, initially stored in stainless steel silos under nitrogen at 12–18 °C, was evaluated after packaging. Tinplate tin (TT) and greenish glass (GG), the most used packaging containers, and temperatures of 6 and 26 °C were taken into consideration. After 125 days from packaging all the samples maintained clearness, green and yellow reflections and the positive sensory notes of bitterness and pungency of the starting EVOO. Shelf-life of EVOO was significantly affected by different storage conditions: oil samples stored in GG at 6 °C preserved for the most part the positive attributes, whereas those stored in TT at 26 °C showed a significant presence of the rancid flavor due to oxidative processes. Moreover, samples stored in GG at 6 °C maintained the highest bitterness intensity and did not show defects at the end of the storage period. The results suggest that storage in GG at a low temperature could represent a promising storage condition to slow-down the oil degradation during market storage

Three-dimensional graphene on a nano-porous 4H-SiC backbone: a novel material for food sensing applications

Sensors which are sensitive to volatile organic compounds and thus able to monitor the conservation state of food, are precious because they work non-destructively and allow to avoid direct contact with the food, ensuring hygienic conditions. In particular, the monitoring of rancidity would solve a widespread issue in food storage. The sensor discussed here is produced utilizing a novel three-dimensional arrangement of graphene, which is grown on a crystalline silicon carbide (SiC) wafer previously porousified by chemical etching. This approach allows a very high surface-to.volume ratio. Furthermore, the structure of the sensor surface features a large amount of edges, dangling bounds, and active sites, which make the sensor, on a chemically robust skeleton, chemically active, particularly to hydrogenated molecules. The interaction of the sensor with such compounds is read out by measuring the sensor resistance in a four wire configuration. The sensor performance has been assessed on three hazelnut samples: sound hazelnuts, spoiled hazelnuts, and stink bug hazelnuts. A resistance variation of about DeltaR = 0.13 (0.02) Ohm between sound and damaged hazelnuts has been detected. Our measurements confirm the ability of the sensor to discriminate between sound and damaged hazelnuts. The sensor signal is stable for days, providing the possibility to use this sensor for the monitoring of the storage state of fats and foods in general.Comment: 11 pages, 6 figures 1 tabl

Evaluation of bread quality and volatile compounds of breads made by sourdoughs fermented by sediments of pulque (xaxtle) as starter culture

Sourdough is an important modern fermentation method of cereal flour and water. The fermentation process is carried out by lactic acid bacteria (LAB) and yeasts which confer specific flavor characteristics to the bread. The main aim of this research was to investigate the bread quality and volatile compounds of breads made by sourdoughs inoculated with sediments of pulque (xaxtle) used it as starter culture. Fifty five volatile compounds were found in the bread made with sourdoughs inoculated with xaxtle from three different regions of Mexico. Using gas chromatography-mass spectrometry, compounds as 3-hydroxy-2-butanone; 3-methyl-1-butanol; 2-methyl, 1-butanol; dimethyl disulfide; furfural, nonanal, phenyl ethyl alcohol and butanoic acid were presented in the flavor profile of the breads and having a positive response to sensory analysis made by evaluators. The xaxtle of Nanacamilpa (XN) and the xaxtle of Villa Alta (XV) were the best breads getting 8.3±0.03, 8.8±0.02, 6.2±0.08 and 8.2±0.01 scores in a scale from 0 to 10 in color, smell, texture and flavor attributes respectively which are positive attributes in favor of the quality bread. As a result of fermentation sourdough with LAB and yeasts from the xaxtle during 24 hours (30° C), the bread made with the sourdough inoculated with xaxtle of Milpa Alta (XM) showed the major acid flavor therefore its sample was less acceptable getting 8.1±0.01, 7.8±0.02, 5.3±0.01 and 7.9±0.01 in the same attributes evaluated. The xaxtle of Nanacamilpa, Tlaxcala (XN) run better than the others as starter fermentation culture for sourdoughs