1,720,960 research outputs found
Lactic acid bacteria in cow raw milk for cheese production: Which and how many?
Get PDFLactic Acid Bacteria (LAB) exert a fundamental activity in cheese production, as starter LAB in curd acidification, or non-starter LAB (NSLAB) during ripening, in particular in flavor formation. NSLAB originate from the farm and dairy environment, becoming natural contaminants of raw milk where they are present in very low concentrations. Afterward, throughout the different cheesemaking processes, they withstand chemical and physical stresses becoming dominant in ripened cheeses. However, despite a great body of knowledge is available in the literature about NSLAB effect on cheese ripening, the investigations regarding their presence and abundance in raw milk are still poor. With the aim to answer the initial question: “which and how many LAB are present in cow raw milk used for cheese production?,” this review has been divided in two main parts. The first one gives an overview of LAB presence in the complex microbiota of raw milk through the meta-analysis of recent taxonomic studies. In the second part, we present a collection of data about LAB quantification in raw milk by culture-dependent analysis, retrieved through a systematic review. Essentially, the revision of data obtained by plate counts on selective agar media showed an average higher concentration of coccoid LAB than lactobacilli, which was found to be consistent with meta-taxonomic analysis. The advantages of the impedometric technique applied to the quantification of LAB in raw milk were also briefly discussed with a focus on the statistical significance of the obtainable data. Furthermore, this approach was also found to be more accurate in highlighting that microorganisms other than LAB are the major component of raw milk. Nevertheless, the variability of the results observed in the studies based on the same counting methodology, highlights that different sampling methods, as well as the “history” of milk before analysis, are variables of great importance that need to be considered in raw milk analysis
Ripening of Nostrano Valtrompia PDO Cheese in Different Storage Conditions: Influence on Chemical, Physical and Sensory Properties
Get PDFNostrano Valtrompia is a hard, long-ripened, Italian Protected Designation of Origin (PDO) cheese typically produced by applying traditional cheesemaking practices in small dairies. Due to the limited production, this cheese is characterized by an important market price. Nostrano Valtrompia physico-chemical and sensory quality can be influenced by the duration and conditions of ripening. The objectives of this work were to characterize the physico-chemical and sensory characteristics of Nostrano Valtrompia cheese ripened for 12 and 16 months and to study the influence of different ripening warehouses: a temperature conditioned warehouse (TCW) and in a traditional, not conditioned warehouse (TNCW). The moisture gradient from the rind to the center of the cheese influenced texture, moisture, aw and color. Ripening in different warehouses did not affect the overall appreciation of the cheese nor other physico-chemical (color, moisture) or sensory traits. TCW cheeses were characterized by a slightly softer texture, slightly different openings distribution, and a different sensory perception than TNCW cheeses. These minor differences were related to the less variable environmental ripening conditions of TCW than TNCW. The results of this study can be useful to support the management of the ripening conditions of Nostrano Valtrompia PDO cheese and to rationally introduce new, suitable ripening sites
Selective enrichment of the raw milk microbiota in cheese production: Concept of a natural adjunct milk culture
Get PDF: In cheese production, microorganisms are usually added at the beginning of the process as primary starters to drive curd acidification, while secondary microorganisms, with other pro-technological features important for cheese ripening, are added as selected cultures. This research aimed to investigate the possibilities of influencing and selecting the raw milk microbiota using artisanal traditional methods, providing a simple method to produce a natural supplementary culture. We investigated the production of an enriched raw milk whey culture (eRWC), a natural adjunct microbial culture produced from mixing an enriched raw milk (eRM) with a natural whey culture (NWC). The raw milk was enriched by spontaneous fermentation for 21 d at 10°C. Three milk enrichment protocols were tested: heat treatment before incubation, heat treatment plus salt addition, and no treatment. The eRMs were then co-fermented with NWC (ratio of 1:10) at 38°C for 6 h (young eRWC) and 22 h (old eRWC). Microbial diversity during cultures' preparation was evaluated through the determination of colony forming units on selective growth media, and next-generation sequencing (16S rRNA gene amplicon sequencing). The enrichment step increased the streptococci and lactobacilli but reduced microbial richness and diversity of the eRMs. Although the lactic acid bacteria viable count was not significantly different between the eRWCs, they harbored higher microbial richness and diversity than NWC. Natural adjunct cultures were then tested in cheese making trials, following the microbial development, and assessing the chemical quality of the 120 d ripened cheeses. The use of eRWCs slowed the curd acidification in the first hours of cheese making but the pH 24 h after production settled to equal values for all the cheeses. Although the use of diverse eRWCs contributed to having a richer and more diverse microbiota in the early stages of cheese making, their effect decreased over time during ripening, showing an inferior effect to the raw milk microbiota. Even if more research is needed, the optimization of such a tool could be an alternative to the practice of isolating, geno-pheno-typing, and formulating mixed-defined-strain adjunct cultures that require knowledge and facilities not always available for artisanal cheese makers
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
Caratterizzazione dei batteri lattici non-starter per il loro controllo in caseificazione
No full textCheese making date his practice over millennia and evolved nowadays being part of a sector representing one of the biggest business of the food industry. In the wide cheese variety, raw milk cheeses have particular economic relevance for many European countries. These products owe their popularity to a typic organoleptic profile whose formation is recognized to be strongly influenced by the raw milk microbiota. Non-starter lactic bacteria (NSLAB) represent the part of this microbiota which has shown the capability to better adapt in the cheese environment and their activity has been positively correlated with cheese flavor formation. Although much is known about the cheese microbiota and from which NSLAB species it is composed, further research has been highlighted as necessary to better understand the origin, development dynamics along the production chain, and metabolic traits at the strain level of NSLAB.
The object of the present thesis was to do a step forward over what is known about the NSLAB, studying their diversity at the strain level through the characterization of their genotypic, phenotypic and metabolic traits. The knowledge of this information is at fundamental for the control of the interested NSLAB within the complex raw milk microbiota and as consequence govern their effect on the cheese's final characteristics.
More than 120 NSLAB strains have been isolated from 20 dairies and screened in order to be qualified as potentially applicable as adjunct cultures. The possibility of positively influencing the cheese characteristic controlling the raw milk microbiota was also investigated by developing a natural adjunct milk culture. Finally, an investigation on hard cheeses produced from centrifugated raw milk gave new insight into the description and consequent prevention of structural defects possibly correlated with the NSLAB abundance unbalancing within the cheese microbiota.
The results achieved lay the foundation to a better exploit of the raw milk microbiota, contributing to the possibility of predicting more precisely the final cheese characteristics. Cheese making trials will be necessary to test the effectiveness of the adjunct strains screened in influencing the cheese aroma. In order to obtain the same goal in the context of an artisanal dairy, more research is needed to optimize the natural adjunct milk culture developed, testing different treatments that could more specifically select desired NSLAB present in raw milk.La produzione di formaggio risale a millenni fa e si è evoluta fino a diventare parte di un settore che oggi rappresenta una delle maggiori attività dell'industria alimentare. Nell'ampia varietà di formaggi presenti sul mercato, quelli prodotti da latte crudo hanno una particolare rilevanza economica per molti paesi europei. Questi prodotti devono la loro popolarità a un profilo organolettico tipico, la cui formazione è riconosciuta essere fortemente influenzata dal microbiota del latte crudo. I batteri lattici non starter (NSLAB, dall’inglese non-starter lactic acid bacteria) rappresentano la parte di questo microbiota che ha dimostrato di meglio adattarsi nel formaggio stagionato per lunghi periodi, e la loro attività è stata correlata alla formazione del sapore e degli aromi tipici del formaggio. Sebbene la ricerca in passato abbia contribuito ad una maggiore conoscenza del microbiota del formaggio e delle specie di NSLAB che lo compongono, è stata evidenziata la necessità di ulteriori ricerche per comprendere meglio l'origine, le dinamiche di sviluppo lungo la catena produttiva e le caratteristiche metaboliche a livello di ceppo dei NSLAB.
L'obiettivo della presente tesi è stato quello di fare un passo avanti rispetto a quanto noto sui NSLAB, studiando la loro diversità a livello di ceppo attraverso la caratterizzazione dei loro tratti genotipici, fenotipici e metabolici. La conoscenza di queste informazioni è fondamentale per il controllo dei NSLAB di interesse caseario presenti all'interno del complesso microbiota del latte crudo e, di conseguenza, per governare il loro effetto sulle caratteristiche finali del formaggio.
Più di 120 ceppi NSLAB sono stati isolati da 20 caseifici e testati per essere qualificati come potenziali colture aggiuntive aromatizzanti. La possibilità di influenzare positivamente le caratteristiche del formaggio controllando il microbiota del latte crudo è stata studiata anche attraverso lo sviluppo di una coltura naturale aggiuntiva in latte. Infine, un'indagine su formaggi a pasta dura prodotti da latte crudo centrifugato ha fornito nuovi spunti per la descrizione e la conseguente prevenzione di difetti strutturali potenzialmente correlati allo squilibrio dell'abbondanza di NSLAB all'interno del microbiota del formaggio.
I risultati ottenuti pongono le basi per un miglior controllo del microbiota del latte crudo, contribuendo alla possibilità di prevedere con maggiore precisione le caratteristiche finali del formaggio. Saranno necessarie prove di caseificazione per testare l'efficacia dei ceppi selezionati nell'influenzare l'aroma del formaggio. Per ottenere lo stesso obiettivo nel contesto di un caseificio tradizionale, sono necessarie ulteriori ricerche per ottimizzare la coltura naturale aggiuntiva in latte sviluppata, testando diversi trattamenti che potrebbero selezionare in modo più specifico i NSLAB desiderati presenti nel latte crudo
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
sophisticated methods
- …
