Cooking behaviour of rice pasta : effect of thermal treatments and extrusion conditions

The effects of pre-gelatinization, mild and severe parboiling processes on paddy rice and the utilization of the corresponding flours (PGF, MPF, and SPF) for gluten-free (GF) pasta-making were investigated. Flour from native rice (NF) was considered as a control. Two pasta-making processes (extrusion-cooking and conventional extrusion) were carried out and seven GF pasta samples, with different thermal treatments without the addition of additives, were obtained. The thermal treatments affected the physical properties and the susceptibility to \u3b1-amylase hydrolysis of rice flours to different extents. The loss of starch granule integrity during the pre-gelatinization process promoted high viscosity at 30 \ub0C and dramatically increased the mass of absorbed water, the amount of soluble components leached out from the granules and the fraction of starch quickly hydrolyzed by \u3b1-amylase. Compared to pre-gelatinization, both parboiling processes induced lower pasting viscosity at any temperature, enzymatic susceptibility, and hydration. The magnitude of these changes significantly increased with the severity of the parboiling treatment. The lowest value for cooking loss was detected for samples prepared by 100% SPF (extrusion-cooking) or by mixture of SPF and PGF (50:50) (conventional extrusion). Nevertheless, the extrusion-cooking process promoted an extremely firm texture of cooked pasta when applied to parboiled flours

Rheological properties and baking performance of new waxy lines : Strengths and weaknesses

In Western countries, the use of waxy wheat in bread-making is gaining interest in view of extending the shelf-life of bread, avoiding the use of additives. Considering the high impact of the environment on wheat properties, selection of waxy lines able to adapt to a particular environment is highly recommended. In this frame, the behavior of three new Italian waxy lines (IW) were compared with that of two waxy lines breeded in United States (USW). Compared to USW, two out of three IW lines exhibited better mixing properties in terms of higher tolerance to mechanical stress (stability and softness index). IW dough showed similar water absorption, stickiness values and visco-elasticity (G\u2032 and G\u2033) compared to USW samples. On the other hand, the waxy wheat lines adapted to the Italian environmental conditions showed a more developed loaf volume with respect to USW lines. The difficulties in dough handling that is typical of waxy wheat when used alone could be partially solved using waxy wheat in combination with non-waxy flours

MACROMOLECULAR CHARACTERISTICS AND BREAD MAKING PROPERTIES OF ITALIAN WAXY WHEAT LINES

This PhD thesis aims to analyse the waxy (amylose-free) wheat (Triticum aestivum L.) properties and the role in the textural characteristics and staling kinetics of bread and bakery products. Moreover, waxy genes effects on qualitative and agronomic characteristics of autochthonous lines selected by a breeding project aimed to obtaining waxy genotypes suitable for cultivation in Italy have been evaluated. The present PhD thesis, therefore, was divided into six chapters: 1.STATE OF THE ART: WAXY WHEAT ORIGINS, CHARACTERISTICS AND APPLICATIONS. Food industry is increasingly interested in waxy (amylose-free) starch because its application to bakery products seems to be able to naturally induce retardation of staling and to extend shelf-life. The starch retrogradation is indeed believed to be the major cause of bread staling and amylose content is assumed to be the main contributor to bread firming. This section offers an overview related to waxy wheat properties and briefly describes how first waxy wheat varieties have been obtained. Moreover, the main composition and thermal properties of waxy starch are illustrated together with the main waxy wheat applications in food products. 2. AGRONOMICAL AND TECHNOLOGICAL PROPERTIES OF ITALIAN WAXY WHEAT.The high influence of different environments on wheat productivity and quality may in principle impede that waxy wheat lines produced in other countries can be successfully cultivated in Italy. In the perspective of developing waxy wheat lines suitable for cultivation in Italy, various research activities have been accomplished since ten years in this country. Aim of the present study has been the evaluation of agronomic and technological performances of a set of 18 Italian waxy wheat lines (IWWL), derived from a breeding program started in 2000 and set up at CRA-SCV (Italy) from partial-waxy cultivars belonging to Italian germplasm. This study shows that, despite the supposed high influence of different environments on wheat productivity and quality, agronomical tests repeated during three years did not allow detecting significant differences between IWWL and two American waxy wheats as well as between IWWL and not waxy wheat in relation to their agronomical characteristics. On the contrary, important differences related to technical characteristics have been observed. Almost all IWWL showed higher bread making qualities with respect to the Amirican waxy and non-waxy wheats used as controls. Six out of eighteen IWWLs analysed showed particularly good performances. In particular, these lines resulted characterized by higher values of gluten index, SDS sedimentation volume, farinograph stability and bread specific volume. Some of these six lines will be further tested during the next growing seasons in three different locations in order to confirm the results achieved.3.PHYSICOCHEMICAL AND STRUCTURAL CHARACTERISTICS OF STARCH FROM ITALIAN WAXY WHEATS. Starch is the most abundant constituent in wheat flours and plays an extremely important role in their pasting properties. The differences in starches amylose/amylopectin ratio result in different pasting properties of flour, and, therefore, in the texture and quality of bakery products. This study aimed to investigate some of the main physicochemical and structural characteristics of waxy starch. In particular, the analyses have focused on thermal and pasting properties of flour from some waxy wheat lines adapted to the Italian environmental conditions, which have been compared with two American waxy wheats and one non-waxy wheat, taken as reference. Results allowed to highlight how the low amylose content of all IWWL (resulted markedly below 1.7% d.b) influences the characteristics of both suspension and dough systems. Waxy wheat samples resulted having a higher number of small starch granules, often with deformities and small cracks with respect to non-waxy wheats. Regarding starch gelatinization, this phenomenon was observed at higher temperatures (as estimated by DSC analyses) in waxy starch with respect to non-waxy starch. Nevertheless, gelatinization temperature is strongly affected by the conditions applied (e.g. water availability, presence/absence of shear-stress, etc.) in the approach used for its evaluation. As the retrogradation extent resulted highly reduced in all the IWWL flours, these types of flours could be usefully exploited for baking processes.4. PROTEIN CHARACTERIZATION AND RHEOLOGICAL PARAMETERS OF ITALIAN WAXY WHEAT LINES. Except for starch properties, there is still limited information about the quality characteristics of complete waxy wheat cultivars and there is a need to better understand how waxy wheat protein composition could affect the physical properties of dough and bakery products. This study analysed the molecular characteristics of proteins from IWWL, comparing the results with those obtained for two samples of American waxy flour and two non-waxy flours with good bread-making quality. The protein content of IWWL flours resulted on average quite high, ranging from 12.0% to 15.4%. The composition observed for the high-molecular weight-glutenin subunits (HMW-GS) of IWWL was generally associated with medium bread-making quality and the electrophoretic analysis indicated that all IWWLs considered have a similar gliadin composition. Differential-solubility data did not show any significant difference between waxy and non-waxy proteins and also the accessibility of sulfhydryls groups seemed to be comparable between IWWL and non-waxy wheat proteins. Front-face fluorescence analyses allowed instead to highlight an interesting difference between IWWL and non-waxy wheat proteins: in fact, dough from IWWL flours needed more water to completely hydrate their proteins, probably as a consequence of the relevant water-retaining capacity of waxy wheat starch. Moreover, the peculiar properties of waxy wheat starch seemed to affect the interactions between protein hydrophobic regions and amylopectin partially solvated regions. Finally, non-waxy flour dough resulted having a much more solid elastic-like behavior with respect to waxy flour dough whereas IWWL flour dough resulted having higher elasticity and consistency indices with respect to American waxy dough. 5. BREAD MAKING CHARACTERISTICS AND STALING KINETICS OF ITALIAN WAXY WHEAT LINES. Waxy wheat is considered to have superior functional properties for bread-making, resulting in the formation of a soft bread-crumb and improving bread shelf-life due to staling retarding. This study focused on the Italian context and considered three Italian waxy wheat lines (IWWL). The properties of dough and the quality of fresh bread obtained by these lines were compared with those of two American waxy wheat samples and a non-waxy flour with high bread-making quality. Bread-making quality has been analysed also in relation to shelf-life. The specific volume of bread samples from IWWLs resulted significantly higher than that of the controls: in fact, the estimated mean area for the large cells of crumb resulted significantly higher for most of the IWWL samples with respect to non-waxy samples. As expected, breadcrumb firmness of all samples from IWWLs resulted lower than commercial flour breadcrumb firmness for 7 days after baking at least. Among IWWLs, bread from wx123 line achieved the highest volume. Its breadcrumb presented the lowest firmness while its breadcrumb moisture was about 3% over that of the commercial flour bread after 7 day storage. During this storage time, the moisture decrease in wx123 bread resulted of 27% against 35% registered for the samples from commercial flour, whereas the decrease in water activity (6%) was the same among all bread samples. This different behavior could partially explain the lower bread firmness detected for wx123 samples. In general, the waxy wheat lines adapted to the Italian environmental conditions showed better bread-making qualities with respect to American standard waxy lines. 6 INFLUENCE OF FLOUR BLENDS ADDED WITH ITALIAN WAXY WHEAT LINE ON BREAD MAKING QUALITY AND STALING KINETICS. Bread samples from waxy flour were typically characterized by higher volume and retarded staling; nevertheless dough from waxy flour had higher stickiness (and consequently a lower machinability) with respect to non-waxy flour. This study aimed at investigating how this negative characteristic could be decreased by using blends of \u201cnormal\u201d wheat flour and IWWL flour, without compromising the other above mentioned good bread-making qualities. Flour blends contained 20% and 40% of commercial flour from non-waxy wheat; the dough and bread properties were compared to American waxy wheat lines used as reference. This approach allowed reducing adhesiveness increasing farinograph stability and dough consistency. The starch retrogradation kinetics wasn\u2019t affected by the presence of commercial flour, as assessed by measuring the firmness of gels stored at low temperatures for long time periods. As regards dough rheological properties, the values registered for the elastic modulus and the viscous modulus in case of waxy dough samples with blends of non-waxy flour varied within the same ranges observed in case of dough samples from pure waxy or pure non waxy flours confirming a solid elastic-like behavior with the elastic modulus prevailing over the viscous modulus also for flour blends dough samples. Concerning bread properties from IWWL flour blends, the specific volumes resulted significantly higher than those of bread samples from non-waxy and American waxy flours. Crust color did not significantly change with respect to breads from 100% IWWL flour excepting for crust redness. The lightness of crumbs increased significantly but remained significantly lower than that of breadcrumb from pure non-waxy flour. As regards bread cells area, the addition of commercial flour in IWWL flour did not determine on average a significant increase in the ratio between cell area and total area of bread cells due to an increase in the density of small cells. Breadcrumbs from blends with 20% of non-waxy flour resulted having good bread-making qualities and maintained low firmness values till 7 days of storage

Stabilit\ue0 dei semi di amaranto dopo soffiatura

L'amaranto (Amaranthus spp.), pianta annuale originaria del Centro America, ha rappresentato per millenni uno degli alimenti base per le popolazioni precolombiane. Produce semi contenenti il 15-20% di proteine ricche di lisina, il 58-66% di amido, il 6-9% di fibra ed il 6-8% di lipidi ad elevato grado di insaturazione. L\u2019amaranto \ue8 attualmente utilizzato in alcuni Paesi dell\u2019America latina in diverse forme: seme intero, farina, seme soffiato ed eventualmente macinato per ottenere farina pregelatinizzata. Se da un lato la soffiatura conferisce al seme caratteristiche particolari, dall\u2019altro lo rende suscettibile all\u2019insorgere di difetti sensoriali dovuti allo sviluppo di rancidit\ue0. Nel presente lavoro si \ue8 voluta indagare l\u2019entit\ue0 dei fenomeni ossidativi in campioni di amaranto soffiato, caratterizzati da un diverso livello di espansione. Sono stati condotti esperimenti di soffiatura, in condizioni di temperatura differenti, operando sia su semi tal quali che previamente sottoposti a trattamenti termici di diversa intensit\ue0, al fine di ridurre l\u2019attivit\ue0 enzimatica nativa. Dopo soffiatura, i prodotti di ciascun esperimento sono stati classificati in tre classi dimensionali (A: diametro medio 1.9 mm; B: 1.6 mm; C: 1.2 mm) e caratterizzati, dopo un periodo di conservazione di 2 mesi a 25\ub0C, mediante valutazione di: peso specifico, attivit\ue0 dell\u2019acqua, umidit\ue0, numero di perossidi, grado di danneggiamento dell\u2019amido, attivit\ue0 lipasica e lipossigenasica. In generale, il trattamento di soffiatura ha determinato, come evidenziano le immagini ottenute attraverso microscopia elettronica in scansione (SEM), un radicale cambiamento della struttura cellulare, con formazione di una matrice molto porosa e fortemente disorganizzata. I semi della classe A hanno presentato una minore umidit\ue0, un maggiore danneggiamento dell\u2019amido, ben evidenziato dalle analisi viscoamilografiche, ed un contenuto pi\uf9 elevato di perossidi. Al contrario, il grado di inattivazione delle lipasi \ue8 apparso simile nei diversi campioni. Le lipossigenasi sono risultate completamente inattivate dal trattamento di soffiatura. L\u2019ossidazione primaria dei lipidi \ue8 risultata statisticamente correlata (P=95%) con il grado di espansione del seme, indipendentemente dalla temperatura di soffiatura utilizzata, ad indicare il ruolo preminente dell\u2019ossigeno (facilitato nel suo contatto con la frazione lipidica dalla struttura alveolata del materiale) nello sviluppo di rancidit\ue0 nei prodotti. I semi meno espansi (classe C) e risultati meno rancidi hanno mostrato al SEM una superficie ancora parzialmente protetta nei confronti dell\u2019ossigeno dalla presenza di porzioni di tegumento ancora aderenti all\u2019endosperma

Influence of the puffing degree on the shel-life of hot-air-puffed amaranth seeds

Puffed amaranth seed is commonly used in South American Countries as a breakfast cereal, as an ingredient in nutritional beverages and in a traditional snack called alegria. The aim of the present study was to evaluate the effect of the expansion degree of the seeds on the enzymatic and non-enzymatic oxidation of the amaranth oil, after two months storage at 25\ub0C. Amaranth seeds were puffed (9 different experiments) with hot air at a temperature ranging between 270\ub0C and 312\ub0C. After puffing, the products of each trial were classified in three groups for dimensions (class A: mean diameter of 1.95 mm; class B: 1.56 mm; class C: 1.17 mm.) and evaluated for moisture, water activity, bulk density, starch damage, peroxide number and lipase activity. The puffing process, as evidenced by the Scanning Electron Microscope (SEM) analysis, radically changed the original grain organization leading to a very porous and highly disorganized structure. Seeds of class A presented a lower moisture content, a higher degree of starch damage, as evidenced by the viscoamylographic and by the enzymatic analyses, and a high peroxides content. On the contrary, the level of lipase inactivation was similar in the different samples. When observed by SEM, the surface of the less expanded products (class C) appeared partially protected against oxygen uptake by the presence of teguments still stuck to the endosperm. Statistical evaluation of the data evidenced that lipid oxidation was solely related to the degree of expansion independently of the puffing temperature. Therefore the possibility of increasing the shelf-life of puffed amaranth should mainly depend on oxygen removal from the package atmosphere

La decorticazione? Anche per il frumento tenero

La decorticazione, convenzionalmente utilizzata nella filiera dei cereali a cariosside vestita, pu\uf2 essere considerata un\u2019operazione innovativa quando applicata al frumento, cereale a cariosside \u201cnuda\u201d. In particolare, a fronte dei risultati positivi ottenuti nel caso del frumento duro, si \ue8 voluto studiare il possibile impiego della decorticazione nella filiera del frumento tenero, valutando gli effetti sulle granelle e sugli scarti di decorticazione, nonch\ue9 sulle farine ottenute. In merito alla decorticazione su impianto pilota, \ue8 stato calcolato il livello di decorticazione (LD, ovvero la percentuale di materiale abraso) e sono stati valutati numerosi indici chimici e fisici. Le condizioni ideali di decorticazione, capaci di garantire LD pari o inferiori al 10%, sono state identificate in una preliminare fase di umidificazione della granella, un continuo rimescolamento del materiale, tempi ridotti di permanenza nel decorticatore, ripetizione del trattamento e utilizzo di mole rivestite di materiale abrasivo di fine granulometria. L\u2019asportazione di una parte dei tegumenti ha permesso di abbreviare sensibilmente i tempi di condizionamento senza compromettere le rese di macinazione. I parametri compositivi delle farine non sono risultati compromessi, quando paragonati con quelli delle farine tradizionali. A seguito di queste valutazioni, il passaggio di decorticazione \ue8 stato inserito nel diagramma industriale di macinazione, con risultati che hanno confermato i trend positivi osservati su scala pilota