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Optimizing storage conditions for minimally processed rocket leaves: effect of temperature and gas conditions on aromatic profile, sensorial and nutritional quality
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Il nome comune di ‘rucola’ è associato a molte specie di vegetali a foglia verde appartenenti alla famiglia delle Brassicacee e caratterizzate da un tipico sapore pungente; nonostante l’alta variabilità tra le specie, Eruca sativa L. e Diplotaxis tenuifolia L. sono le più diffuse. Dal punto di vista nutrizionale, la rucola fornisce un vasto range di fitonutrienti e minerali come provitamina A, vitamina C, flavonoidi, glucosinolati, fibre, potassio e zolfo. Il consumo di rucola permette di introdurre nella nostra dieta nutrienti che presentano diversi benefici per il corpo umano, molti dei quali hanno attività diuretiche, antinfiammatorie, stimolanti, depurative ed epatoprotettive.
La rucola dal punto vista commerciale è molto apprezzata in Europa proprio per il suo sapore tipico e per la sua consistenza; normalmente è consumata cruda come componente di insalate. In seguito all’aumento della richiesta e del consumo riscontrati negli ultimi anni, la rucola è principalmente venduta lavata e imbustata come prodotto di IV gamma. La shelf-life della rucola di IV gamma dipende dalle condizioni di conservazione e dalle operazioni di produzione dell’alimento; questi fattori potrebbero accelerare i processi di degradazione, indurre avvizzimento, perdita di colore e degli attributi sensoriali come aroma e sapore. In questo studio sono stati valutati gli effetti di diversi fattori sulla shelf-life della rucola di IV gamma al fine di ottimizzare le condizioni di conservazione attraverso la gestione della temperatura e della composizione dei gas all’interno della confezione. Per analizzare l’effetto della temperatura sulle cinetiche di degradazione degli attribuiti sensoriali, fisici e chimici in funzione della temperatura di conservazione, è stato confrontato il modello di Weibull con il modello convenzionale di primo ordine. Il modello di Weibull ha permesso di descrivere accuratamente la forma e la pendenza delle curve di degradazione degli attributi qualitativi considerati e ha mostrato un’alta abilità nel fittare i dati sperimentali rispetto al modello convenzionale di primo ordine. Questi risultati permettono anche di stabilire quali possano essere i fattori limite per la durata della vita commerciale della rucola, come l’aspetto visivo ed il contenuto di acido ascorbico. Come secondo obiettivo parziale diverse concentrazioni di ossigeno (0.5, 3 e 6 kPa) e di anidride carbonica (5, 10 e 20 kPa) sono state testate, indipendentemente l’una dall’altra, per analizzare i loro potenziali effetti positivi e negativi sugli attributi qualitativi della rucola fresca durante la conservazione. In generale le concentrazioni di ossigeno considerate non hanno avuto un alto impatto sulla qualità della rucola fresca durante la conservazione, gli attributi sensoriali sono stati maggiormente preservati nelle foglie conservate con 3 e 6 kPa di ossigeno, mentre concentrazioni al di sotto di 0.5 kPa hanno avuto un impatto negativo sulla shelf-life della rucola. I benefici associati all’impiego di alte concentrazioni di CO2 sono stati più evidenti rispetto a quelli ottenuti usando basse concentrazioni di O2, infatti l’aspetto visivo della rucola conservata con CO2 rispetto a quella conservata in aria si è mantenuto più elevato. Nonostante i buoni risultati ottenuti per l’aspetto visivo, la rucola quando conservata con 20 kPa CO2 ha prodotto cattivi odori. In conclusione, gli studi svolti sulla composizione dei gas hanno indicato che concentrazioni estreme di O2 pari a 0.5 kPa, e l’accumulo di CO2 sopra i 20 kPa dovrebbero essere evitati durante la conservazione della rucola, mentre l’aggiunta di una quantità pari a 10 kPa di CO2 all’aria potrebbero preservare la qualità della rucola. L’effetto della temperatura è stato inoltre valutato sulla rucola di IV gamma imbustata in atmosfera modificata passiva (MAP). La cinetica degradazione degli attributi qualitativi è stata modellata matematicamente in condizioni isotermiche e non isotermiche al fine di migliorare la gestione della catena logistica di produzione in funzione della sua storia termica. Una forma cumulativa dell’equazione di Weibull e del modello log-logistico ha permesso di fittare i dati sperimentali nel tempo e di studiare la degradazione degli attributi sensoriali, fisici e chimici in dipendenza dalla temperatura. Gli effetti positivi della conservazione in MAP potrebbero essere persi se nella confezione si creano condizioni di anaerobiosi in seguito ad una gestione impropria della fase di imballaggio. A tal fine, sono stati analizzati i cambiamenti della composizione volatile della rucola conservata in MAP in condizioni isotermiche (5°C) e non isotermiche simulando la masticazione dell’alimento attraverso l’omogeneizzazione del campione. La conservazione in MAP ha permesso di preservare la freschezza del prodotto in termini di aspetto visivo e mantenimento dell’odore tipico. Tuttavia, nell’ultimo giorno di conservazione è stato osservato un aumento della produzione di dimetil-solfuro e acetaldeide, i quali potrebbero conferire rispettivamente note di zolfo ed etereo alla percezione dell’odore della rucola. La fluttuazione della temperatura ha indotto cambiamenti nel profilo dei volatili, rispetto a quanto osservato nella condizione di conservazione isotermica, che vengono mantenuti anche dopo il ripristino della catena del freddo. Infine in un ulteriore esperimento i volatili sono stati monitorati direttamente nello spazio di testa della confezione per valutare l’effetto della composizione dei gas e della temperatura sui composti responsabili dell’odore percepibile dopo l’apertura della busta. I cambiamenti nel profilo dei volatili sono stati valutati sulla rucola confezionata e conservata a 0, 5 e 15°C, e, nel caso della conservazione a 5°C, i risultati sono stati confrontati con un controllo in aria. All’aumentare della temperatura si verifica un’accelerazione dei processi degradativi e questo induce lo sviluppo di cattivi odori. Durante la conservazione a 15°C è stata osservata infatti una maggiore produzione di derivati lipidici e di composti solforati rispetto alla conservazione a temperature più basse; l’aroma tipico viene mantenuto a 0°C, temperatura alla quale non sono stati osservati processi degradativi. Gli effetti della conservazione in MAP, valutati tramite confronto con il controllo in aria, sono stati molto più bassi rispetto a quelli relativi all’impiego di diverse temperature; la percezione di cattivi odori nella rucola in MAP è risultato essere maggiore rispetto a quella riportata per la conservazione in aria. Questi risultati contribuiscono ad aumentare la conoscenza sulle reazioni di degradazione che si verificano durante la conservazione della rucola a differenti temperature e composizione dei gas, fornendo importanti informazioni per migliorare la gestione dei punti critici di controllo e per mantenere la qualità durante l’intera catena di produzione.
Abstract
‘Rocket’ is a collective name to indicate many species of green leaves belonging to Brassicacea family and characterized by a tipical pungent taste. Although the great variability and number of rocket species, Eruca sativa L. and Diplotaxis tenuifolia L. are the most common species; they are a source of a wide range of phytonutrients, such as provitamin A, vitamin C, flavonoids, glucosinolates, fiber, potassium and sulfur. Beneficial effects have been associated to the consumption of rocket due to the employment/ingestion of nutrient compounds characterized by diuretic, anti-inflammatory, stimulant, depurative, hepatoprotective and stomathic activities. Rocket leaves are very appreciated in Europe for their typical taste and texture and are manly consumed raw in salads. Due to the increased e consumption in the recent years, rocket it’s mainly sold as a ready-to-eat product, which has been washed and packaged. The shelf-life of ready-to-eat rocket is principally limited by the storage conditions and processing operations, which may accelerate the degradation process, inducing wilting, discoloration, loss of nutritional properties and sensorial attributes as aroma and flavor. In this study was investigated the effect of several factors on the shelf-life of ready-to-eat rocket leaves in order to optimize the
storage conditions through a correct management of the temperature and the gas composition inside the packaging. The effect of temperature on the degradation kinetics of sensorial, physical and chemical attributes of rocket leaves was studied. Weibull model was compared to conventional first-order model to describe quality changes over time in function of the temperature. Weibull model showed an higher ability to fit experimental data compared to conventional first-order models, allowing to accurately describe shape and slope of the degradation curves. Obtained results also permitted to establish the most limiting factors for shelf-life of rocket leaves, which was therefore estimated in term of appearance score and ascorbic acid. As second partial objective different concentrations of O2 ( 0.5, 3 and 6 kPa) and CO2 (5, 10 and 20 kPa) were independently tested to evaluate their potential beneficial or negative effects on qualitative attributes of fresh rocket during storage. Generally different oxygen concentrations did not had a high impact on quality of rocket leaves, resulting in a slightly high sensorial quality for the leaves stored under 3 and 6 kPa O2, whereas O2 concentrations below 0.5 kPa negatively affected the shelf-life of rocket leaves. On the other hand, the effects of high CO2 were more evident than those of low oxygen, indicating that the visual appearance was better preserved in presence of CO2 compared to the storage in air. Despite this positive effect on appearance a strong production of off-odors was observed for rocket stored with 20 kPa CO2, whereas level of 10 kPa CO2 did not induced any off-odor development. In conclusion results of the experiments on gas composition suggested that extreme gas concentrations with oxygen level of 0.5 kPa O2 and accumulation of CO2 up to 20 kPa should be avoided, whereas the addition of 10 kPa CO2 to the air preserved the quality of the rocket leaves. The effect of the temperature on rocket leaves packaged in passive modified atmosphere (MAP) was also evaluated. Degradation kinetics of the quality attributes on fresh-cut rocket were modeled in isothermal and non isothermal conditions in order to improve the management of the logistic chain according to the product thermal history. In particular, the cumulative form of the Weibull equation and a log-logistic model were, respectively, used to fit the experimental data over time and to study the temperature dependence of the degradation rates for several sensorial, chemical and physical attributes. Moreover, since MAP beneficial effects can be lost if anaerobic conditions develop inside the packaging due to an improper packaging management, volatile changes in MAP stored rocket leaves were analyzed in isothermal (5°C) and non isothermal conditions, by homogenizing the samples, and therefore simulating the chewing process. Storage in MAP had a beneficial effect on the quality of rocket leaves preserving the freshness of the produce in terms of visual quality and retention of the typical odor. However, at the last days of storage an increased production of dimethyl sulfide and acetaldehyde was observed, which could respectively confer the typical sulfurous and ethereal odor to the produce. Moreover, temperature fluctuation induced changes in the volatile profile compared to rocket stored in isothermal conditions which persisted even when the cold chain control was restored. The last experiment was aimed to monitor the volatiles directly accumulated in the headspace of the packages to evaluate the effect of gas composition and temperature on the compounds responsible of the perceived odor after the opening of the package. Rocket leaves were packed and stored at 0, 5 and 15°C; additionally at 5°C a control in air was also included to test the effect of gas composition on volatile profile. Temperature played an important role by accelerating the degradation rate of the rocket leaves inducing the development of off-odors. At 15 °C temperature lipid derivatives and sulphurous compounds were in fact produced in much higher quantity than at low temperatures. The typical aroma was best preserved at 0°C, in which no degradation process was observed in the last days of storage. The effect of the MAP conditions compared to the control in air, was much lower than the
effect of the temperature, with an higher perception of off-odors for MAP stored samples than for samples stored in air. All the results contributed to increase the knowledge on degradation reactions occurring during storage of rocket leaves under different temperature and gas conditions, providing important tools to improve the management of the critical control points and quality maintenance during the entire production chain
Application of multivariate accelerated test for the shelf life estimation of fresh-cut lettuce
No full textThe aim of this paper was to obtain a more realistic shelf life estimation of fresh-cut lettuce by considering several sensorial, physical and chemical attributes. The Multivariate Accelerated Shelf Life Testing (MASLT) approach was applied, comparing the use of the traditional zero- and first- order reactions with the Weibullian logistic model in describing score change kinetics over time. A total variance of 79.6% was explained by two principal components (PC): PC1 (68.8%) and PC2 (10.8%). The multivariate degradation kinetics was better described by a zero-order reaction, yielding an r2 value greater than 0.97, while the temperature dependence of the multivariate rate constant, km, was well-fitted by the log-logistic model. A cut-off criterion of -1.52 was calculated, leading to shelf life estimations of ∼12.4, ∼10.4 and ∼3.7 days for fresh-cut lettuce stored at 0, 5 and 15 °C, respectively. This method provides an overall and accurate description of the degradation phenomena occurring during the storage of fresh-cut lettuce
Effect of temperature abuse and improper atmosphere packaging on volatile profile and quality of rocket leaves
No full textThis study aimed to investigate the effect of temperature abuse and improper packaging on volatiles profile, vitamin C and sensorial attributes of rocket leaves packaged in modified atmosphere. Leaves packed in suboptimal conditions (high ratio of product weight/bag surface) were stored for 10 days at 0 and 5 °C, and for 8 days at 15 °C. Rocket leaves were kept in macroperforated bags in order to prevent modification of atmosphere within the headspace (as control). The packed rockets at 0 °C retained ascorbic acid content while it decreased during storage at higher temperatures. The main losses in the appearance and vitamin C content were observed when the O2level reached about 0 kPa corresponding to the highest CO2accumulation in the bag (25 kPa). The off-odors from dimethyl sulfide (DMS), dimethyl disulfides (DMDS) and other volatiles were produced at 5° and 15 °C, changing the initial headspace fingerprint, which was best preserved at 0 °C. Results of this work showed that improper packaging condition may decrease the shelf-life of rocket leaves compared to storage in air, inducing loss of appearance score, the production of off-odors and the degradation of Vitamin C. No additional benefit was obtained by optimal gas composition when bags were stored at 0 °C, indicating that the use of low temperature was effective to slowing down degradation reactions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
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koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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