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Biotechnological strategies to improve the quality of enriched cereal foods
No full textIn the first part of the present PhD thesis project, a dry fractionation process was applied to common wheat kernels. In particular, a pigmented (purple) commercial variety underwent a pre-milling debranning treatment to separate and selectively recover tissues with different composition and functional properties. The removed fractions were then used for the production of enriched pasta by a roll-sheeting process and a drying cycle at LT
Biotechnological actions to improve the quality of enriched cereal foods
No full textThis PhD project is aimed to obtain enriched foods with enhanced overall quality by applying biotechnological approaches that would modify the structural properties of specific macromolecules (such as non-starch-polysaccharides, polyphenols, etc.) present in cereals and pseudocereals
Effect of (bio-)technological approaches on bran to improve the quality of cereal products
No full textThis communication reports the main results of the following activities:
(A1) Production and characterization of customized fractions by pre-milling debranning of purple wheat (A1.1). Production and quality evaluation of cereal-based products (i.e. pasta) rich in bioactive compounds (A1.2).
(A2) Assessment of the effects of bran particle size and enrichment levels of pseudo-cereal by-products (i.e. buckwheat bran) on wheat-based bread quality.
(A3) Evaluation of the effects of physical treatments (i.e. SHS – Super Heated Stem), alone (A3.1) or in combination with enzymatic treatments (A3.2) on the techno-functionality of buckwheat bran in wheat bread.
(A4) Production and characterization of customized fractions by air classification treatments of buckwheat bran
EFFECT OF (BIO-)TECHNOLOGICAL APPROACHES ON BRAN TO IMPROVE THE QUALITY OF CEREAL PRODUCTS
Full text linkThe design of foods enriched in dietary fiber has recently received great attention among academia and food industry, since in many European countries the daily intake of dietary fiber is much lower than the recommended levels (25 g; EFSA, 2010). Being a staple food category, cereal products may represent a valid resource to satisfy the optimal amount of soluble and insoluble fiber and other bioactive components. Despite the nutritional benefits, the incorporation of fiber into flour negatively affects the textural and sensory properties of bread and pasta products.
This PhD project dealt with the application of physical and/or biotechnological strategies to modify the structural properties of peculiar macromolecules (such as non-starch-polysaccharides or proteins) to enhance the quality of fiber-enriched foods. Samples from the outermost layers of cereals and pseudocereals particularly rich in bioactive compounds (e.g. purple wheat and buckwheat) were included in pasta or bread after treatment and evaluated in terms of technological behavior.
The first part of the thesis regarded the application of a two-step debranning process to purple wheat that allowed the selective recovery of bioactive compounds, such as fiber and phenolic compounds. Debranned fractions from the first and the second step were used separately to produce fiber-enriched pasta. Bran from conventional milling was also used as a control. Both fractions had higher or comparable content in total and soluble fiber than bran. Moreover, both of them exhibited a higher ferric reducing-antioxidant power (FRAP) than bran, whereas the highest amount of anthocyanins was found in the first fraction. When compared with pasta enriched in bran, the samples enriched either in the first or second fraction had similar FRAP values and higher amount of anthocyanins, while retaining a fair cooking quality.
In the second part of the thesis micronization was applied to buckwheat bran to evaluate the effect of granulometry on dough/bread quality. The role of coarse and fine buckwheat bran enrichment on wheat dough was studied at increasing levels (5, 10, 20%). Dough and bread properties were negatively affected by the interplay of bran addition level and particle size. The thermo-mechanical behavior of dough was found to be mainly related to starch phase transitions during heating with no regards of particle size. Front-face fluorescence studies reveled differences in gluten structural arrangement and solvation with a distinct effect of particle size. Despite the better or similar dough rheological properties (e.g. elasticity, resistance to extension, extensibility), bread enriched in fine bran had lower baking quality in comparison with samples enriched in coarse bran, in terms of loaf specific volume and crumb softness. Concerning the texture, the variations in the perceived crumb hardness were mainly related to changes in crumb density. The application of an adapted Ashby-Gibson model to correct hardness values for the variation in density revealed that the mechanical properties of the solid crumb matrix were controlled by the differences in moisture and in bran volume fraction.
Buckwheat bran was used also to evaluate the effects of superheated steam (SS) on bran properties. SS is an innovative technology that has allowed drying of many food matrices while limiting collateral effect on the product. After screening the process conditions, the selected treated bran samples (120 °C, 140 °C, or 160 °C; 40 min; 0.7 aw) were incorporated into high-enriched dough (20%) and their influence on the rheological properties and on the baking quality were considered. The treatment deeply affected the chemical/physical properties of buckwheat bran. In particular, changes in water affinity were progressively observed with increasing temperature, also due to the formation of protein aggregates. These modifications influenced the thermo-mechanical properties of high-bran enriched doughs that reflected baking behavior. When appropriate setting was chosen (temperature: 160 °C) SS treatment increased buckwheat bran performances in terms of specific volume and crumb softness in comparison with untreated bran.
The last part of the thesis regarded the use of specific enzymatic treatment (i.e. pectinases and cellulases) to decrease the size of non-starch-polysaccharide chains, aiming at mitigating the worsening effects of fiber on enriched products. Either coarse buckwheat bran or SS bran (treated at 140 °C; 40 min; 0.7 aw) were used. From a technological standpoint, the preliminary bran treatment with cellulases could be a feasible solution to produce bread enriched in buckwheat bran. Besides this, no synergistic effect was observed between SS treatment and enzymatic treatment.
Future studies will include the assessment of the effects of bran-treatments on the macromolecular structure of fiber, to define not only its rheological performance but also its nutritional functionality
Including buckwheat bran in wheat dough and bread: what happens?
No full textDevelopment of products rich in ingredients with high nutritional value –as dietary fiber– is currently one of the most important goals for food companies.
However, inclusion of high levels of fiber in cereal-based products is still technologically challenging, as for the texture and the sensory quality.
Buckwheat is a nutritionally-relevant pseudo-cereal and is traditionally used in Europe and Asia for pasta production, but rarely exploited in bakery applications.
In this study, we investigated the effects of enriching wheat flour with increasing levels of buckwheat bran (5, 10, 20%), before and after micronization.
DMTA and DSC allowed evaluating the effects of bran on the thermo-mechanical transition during processing while dough rheology at large deformations was assessed by the Kieffer test. Standard baking tests and TPA were performed on bread.
Regarding dough properties, both DMTA and DSC showed that bran enrichment resulted in increase in the temperature of starch gelatinization. The size of the effect depended on bran amount and particle size. DMTA also provided evidence as for changes in the viscoelastic behavior during heating. As for Kieffer test results, increasing bran inclusion led to a decrease of resistance to extension.
Concerning the baking quality, the decrease in loaf volume due to buckwheat enrichment clearly depended on the level of inclusion and on bran particle size. Moisture content of fresh bread reflected the behavior in dough hydration for both types of bran: gradual enrichment with buckwheat as such led to a more wet product, whereas the substitution level with micronized bran had no significant effect. Crumb firmness increased as the bran content increased and was positively correlated with crumb density. The Ahsby-Gibson theory for cellular solid was applied to correct for the effect of density. Bran as such increased the corrected hardness for addition level higher than 10%. On the contrary, micronized bran deeply altered crumb firmness already at 5% substitution level.
Overall, buckwheat bran greatly affected dough rheology and thermal transitions during baking, which resulted in considerable changes in bread quality. Such changes could be related not only to the enrichment degree but also to the size of the bran particles
Effect of buckwheat bran enrichment on wheat dough and bread properties
No full textThe production of foods rich in dietary fiber represents one of the most important driving forces in the development of innovative cereal-based products. However, inclusion of high levels of fiber is still technologically challenging, as for the texture and the sensory quality.
Buckwheat is a nutritionally-relevant pseudo-cereal and is traditionally used in Europe and Asia for pasta production, but rarely exploited in bakery applications.
In this study, we investigated the effects of enriching wheat flour with increasing levels of buckwheat bran (5, 10, 20%), with different particle size (dav bran as such: 360 μm; dav micronized bran: 110 μm).
Dynamic Mechanical Thermal Analysis (DMTA) and differential scanning calorimetry (DSC) allowed evaluating the effects of bran on the thermo-mechanical transition during processing. Dough rheology at large deformations was assessed by the Kieffer test. Standard baking tests and texture profile analysis were performed on bread in small-scale trials (60g puffy loafs).
As for the dough properties, both DMTA and DSC approaches indicated that bran enrichment resulted in a progressive increase in the onset temperature of starch gelatinization. DMTA also provided evidence as for changes in the viscoelastic behavior during heating associated with bran enrichment. As for the dough behavior at large deformations, dough resistance to extension decreased with increasing bran inclusion. On the contrary, no univocal behavior was assessed as for the dough extensibility increase.
As for baking quality, the decrease in loaf volume due to buckwheat bran enrichment clearly depended on the level of inclusion and on bran particle size. Crumb moisture content of fresh bread reflected the behavior in dough water absorption for both types of bran: gradual enrichment with buckwheat as such led to a wet product, whereas the substitution level with micronized bran has no significant effect. Crumb firmness increased as the bran content increased and was positively correlated with the increase in crumb density. For this reason, the Ahsby-Gibson theory for cellular solid foods was applied. Bran as such increased the corrected hardness for addition level higher than 10%. On the contrary, the addition of micronized bran deeply altered crumb firmness already at 5%.
The inclusion of buckwheat bran greatly affected dough rheology and thermal transitions during baking, which resulted in considerable changes in bread quality. Such changes could be related not only to the enrichment degree but also to the size of the bran particles
Master bag low-oxygen packaging system: Quality evolution of ground beef patties during storage, blooming and display presentation
No full textCase-ready ground beef patties have been packed using a low-oxygen master bag packaging system with
oxygen scavengers consisting in: storage for 10 days in low oxygen master bag (0.5 C), blooming for
different times and display life in air for 2 days (5 C). The kinetics of blooming was studied as well as the
effect of a PVC stretch film (with an O2TR – oxygen transmission rate – equal to 20,000cm3m2 24 h1
(23 C, 0% RH, 1 bar of pO2) with or without perforation on myoglobin oxygenation and color changes.
During storage in master bags, the scavengers allowed the progressive conversion of surface
oxymyoglobin into deoxymyoglobin through the reversible formation of metmyoglobin (transient
discoloration). The microflora shifted from aerobic to anaerobic with a predominance of lactic acid
bacteria. The concentration of Brochotrix thermosphacta remained constant over the entire storage period.
The removal of the trays from the master bag and the subsequent storage in air allowed the blooming of
the meat within 60 min. The high O2TR value of the stretched PVC guaranteed rapid oxygen exchange,
whereas the presence of the perforation did not contribute to a further increase in the superficial
oxygenation. The quality decay during the display life was comparable to that of samples never stored in
master bags. In conclusion, the use of low oxygen master bags was able to prolong the storage time on
ground beef patties ensuring the current shelf life achieved with traditional packaging system
Valutazione dell’impatto ambientale della riduzione di spessore di un packaging secondario
No full textNella progettazione di un imballaggio per alimenti sono importanti l’attenzione alla qualità e alle proprietà del prodotto ma anche i potenziali impatti ambientali legati alla sua produzione e uso. Sono diverse le azioni di prevenzione che possono essere attuate per migliorare la sostenibilità dell’imballaggio: la riduzione di materia prima impiegata, mantenendo le stesse prestazioni, risulta essere una soluzione tra le più adottate ed efficaci.
Scopo di questo lavoro è stata la valutazione della diminuzione del potenziale carico ambientale di un film termoretraibile in LD-PE e MD-PE, in seguito alla riduzione di spessore da 50 a 40 μm. Il film è stato prodotto in un impianto industriale di coestrusione a tre strati con tecnologia di soffiaggio in bolla (Blow Up Ratio 1:3).
Poiché la funzione principale di un imballaggio secondario è quella di raggruppare contenitori primari per permetterne la protezione e la movimentazione, sono state comparate inizialmente le proprietà meccaniche dei due campioni. In particolare sono state effettuate le seguenti analisi: carico alla rottura, modulo di elasticità, coefficiente di frizione statico e dinamico (secondo metodi ASTM), nonché la termoretrazione longitudinale e trasversale in olio (secondo metodo interno).
L’analisi degli impatti ambientali è stata svolta tramite metodologia LCA (Life Cycle Assessment) semplificata utilizzando il software SimaPro®. L’unità funzionale è stata definita come la quantità di materiale necessario per produrre un singolo fardello (735 x 1230 mm), i confini del sistema definiti secondo l’approccio “from gate to delivery”, cioè dalla produzione in azienda fino al trasporto al cliente.Per la fase di inventario sono stati utilizzati dati primari, raccolti tramite questionari forniti all’azienda produttrice del film plastico. I dati mancanti sono stati selezioni dal database Ecoinvent. L’analisi ha permesso di definire i seguenti impatti ambientali: potenziale di riscaldamento globale, potenziale di riduzione dello strato di ozono, potenziale di ossidazione fotochimica, potenziale di acidificazione e di eutrofizzazione, uso di fonti fossili non rinnovabili.
Le analisi meccaniche permettono di affermare la buona comparabilità prestazionale dei due film, rendendo possibile la produzione e l’utilizzo di un film a ridotto spessore. L’analisi LCA conferma inoltre gli effetti ambientali positivi ottenuti grazie al risparmio di materia prima
Evoluzione della qualità di carne bovina a fette confezionata in atmosfera protettiva in combinazione con assorbitori di ossigeno
No full textOggetto del presente lavoro è stata la valutazione della qualità di carne bovina a fette (Semitendinosus) durante e in seguito alla conservazione in anossia in un sistema “master bag”. Tale sistema di confezionamento prevede l’inserimento di vassoi “case-ready” e di assorbitori di ossigeno all’interno di un “master bag” barriera poi chiuso ermeticamente in atmosfera modificata (30% CO2, 70% N2).
La presenza degli assorbitori di ossigeno garantisce il mantenimento dell’anossia per tutta la durata della conservazione nel sacco. Tale condizione è infatti fondamentale per preservare la qualità del prodotto poiché le basse concentrazioni di ossigeno possono causare l’ossidazione irreversibile dei pigmenti compromettendo quindi l’accettabilità del prodotto. Si è voluto sottoporre alla sperimentazione lo stesso taglio bovino proveniente da due diverse razze (Piemontese e Argentina) con differente storia prima del porzionamento (rispettivamente di frollatura aerobica e sottovuoto, entrambe a 2±1°C). Durante tutte le fasi di conservazione (storage life, blooming e display life) sono stati valutati indici microbiologici, colorimetrici e spettrofotometrici (stima delle forme mioglobiniche superficiali), oltre all’acquisizione delle immagini tramite scanner.
Entrambe le tipologie di carne sono state conservate in “master bag” per almeno 21 giorni, durante i quali non si è riscontrato un
decadimento significativo degli indici qualitativi. Questo risultato può essere anche spiegato dalla funzione sequestrante degli assorbitori: infatti, già a partire dal secondo giorno di conservazione non è stato più possibile rilevare la presenza di ossigeno all’interno dei sacchi.
In seguito all’apertura del “master bag” i pigmenti superficiali si riossigenano e conferiscono al prodotto il colore rosso acceso tipico della carne fresca. Grazie alla ripresa della colorazione è stato possibile esporre i prodotti in un display refrigerato per simularne la vita di scaffale nel punto vendita. L’esposizione nel banco frigo è stata condotta per 4 giorni durante i quali si è osservata la graduale ossidazione dei pigmenti superficiali che ha comportato il viraggio del colore verso tonalità marroni. La degradazione del prodotto durante la “display life” non è risultata favorita dal confezionamento in “master bag” rispetto a quello tradizionale (tray wrap). È quindi possibile concludere che il sistema di confezionamento in “master bag” garantisce un aumento della vita commerciale di differenti tipologie di carne bovina a fette fino a 21 giorni, senza compromettere l’accettabilità del prodotto
Characterization of new milling fractions and use of biocomponents-enriched fractions in pasta production
No full textThe conventional milling process usually does not allow for the selective recovery of bioactive compounds, such as fiber or antioxidants, that are collected in bran and germ. Dry fractionation processes may represent a convenient method for achieving this goal. Debranning is a widespread dry-process for covered cereals as rice, consisting in sequential and alternate steps of friction and abrasion. If applied to wheat, it allows the partial removal of the external coats and of the aleurone layer, allowing to recover tissues with different composition and functional activities.
The debranning was applied to purple wheat, a naturally antioxidant-rich variety. Wheat was hydrated and then debranned, removing the 3.7% of the whole grain (DF1). The step was repeated to obtain a final 9.7% of debranned material (DF2)
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