Analytical approaches for discriminating native lard from other animal fats

Establishing the distinguishable characteristics of lard from other common animal fats might be helpful for authentication initiatives in foods and feeds. In this study, fatty acid and triacylglycerol compositions, thermal and spectroscopic characteristics of native lard (NL), respectively, were compared with those of beef tallow (BT), mutton tallow (MT), and chicken fat (CF) by using gas liquid chromatography (GLC), high-performance liquid chromatography (HPLC), and differential scanning calorimetry (DSC). GLC analysis showed that the comparison of the overall fatty acid data might not be suitable for the discrimination of different animal fats, but the use of the principal component analysis and the percent palmitic acid enrichment factor [PAEF (%)] calculations were useful. HPLC analysis showed that NL displayed a TAG profile, which was quite different from those of either BT or MT, but appeared to be closely similar to that of CF. Results of DSC thermal analysis showed that both melting and crystallization curves of NL were remarkably different from those of other animal fats

Stabilization of Arthrospira platensis with high-pressure processing and thermal treatments: Effect on physico-chemical and microbiological quality

Arthrospira platensis (Spirulina) is a cyanobacterium that has been recently studied for food applications due to its high biological and nutritional value. When A. platensis is used as an ingredient in food applications, proper treatments have to be applied in order to reduce microbial contamination. This work compared the effect of thermal treatments (sterilization at 121℃ and pasteurization at 90℃) and high-pressure processing (400, 600 MPa) on the chemical, physico-chemical, and microbial quality of 5% (wt/vol) A. platensis aqueous suspensions. Total antioxidant capacity, total polyphenols content, color, and pigments content were not strongly lowered/modified by the high-pressure processing (HPP) treatments. HPP at 400 MPa even improved the release of C-phycocyanin from the biomass because of the breakage of cell walls. HPP treatments were comparable to pasteurization in reducing yeasts, coliforms, Staphylococci, and total bacterial count. Conversely, sterilization was the only treatment that guaranteed the inactivation of spore-forming species but affecting the final quality. Novelty impact statement: High-pressure processing (HPP) treatments were found to be a good strategy to preserve or even improve some physical and chemical properties of Arthrospira platensis (Spirulina), in particular antioxidant capacity, polyphenols, color, and pigments content. Furthermore, HPP treatments were comparable to pasteurization in reducing microbial cell count, while sterilization was the only treatment able to ensure the inhibition of spore-forming species

Lactobacillus paracasei 4341 as adjunct culture to enhance flavor in short ripened Caciotta-type cheese

Caciotta is the name used to define a type of Italian semi-hard cheese Caciotta-type cheese. Due to the short ripening time, pasteurization is necessary to eliminate the potential pathogenic bacteria, which may be present in raw milk, causing also the reduction of ripened cheese flavor. The purpose of this research was to evaluate the effect of a selected wild Lactobacillus paracasei strain experimentally used as adjunct culture to enhance the flavour formation in a short-ripened caciotta-type cheese. An integrated polyphasic approach was used to compare the experimental and control Caciotta produced in a company located in Emilia Romagna region (Italy). It was demonstrated how the L. paracasei 4341 was able to develop in curd and cheese interacting with the acidifying commercial starter. The main acidifying starter species, were differently affected by the presence of the adjunct culture. Streptococcus thermophilus shown comparable behavior in all cheese-making step of control and experimental Caciotta, while Lactobacillus delbrueckii subsp bulgaricus, growth was slowed down by the presence of the adjunct culture during the whole ripening time. The higher amount of volatile compounds and organic acids due to the adjunct L. paracasei 4341 lead to a clear differentiation of the experimental Caciotta respect to the control, in terms of aromatic profile, color, texture and sensorial perception

Applicability of Confocal Raman Microscopy to Observe Microstructural Modifications of Cream Cheeses as Influenced by Freezing

Confocal Raman microscopy is a promising technique to derive information about microstructure, with minimal sample disruption. Raman emission bands are highly specific to molecular structure and with Raman spectroscopy it is thus possible to observe different classes of molecules in situ, in complex food matrices, without employing fluorescent dyes. In this work confocal Raman microscopy was employed to observe microstructural changes occurring after freezing and thawing in high-moisture cheeses, and the observations were compared to those obtained with confocal laser scanning microscopy. Two commercially available cream cheese products were imaged with both microscopy techniques. The lower resolution (1 µm/pixel) of confocal Raman microscopy prevented the observation of particles smaller than 1 µm that may be part of the structure (e.g., sugars). With confocal Raman microscopy it was possible to identify and map the large water domains formed during freezing and thawing in high-moisture cream cheese. The results were supported also by low resolution NMR analysis. NMR and Raman microscopy are complementary techniques that can be employed to distinguish between the two different commercial formulations, and different destabilization levels

Approcci statistici, chemometrici e computazionali per favorire la qualità e aumentare il mercato di formaggi freschi ed a lunga stagionatura

Globalization of food markets and the increasing demand for some highly perishable and traditional Italian cheeses, forced the dairy sector to investigate in new methods to improve export and/or to control compliance with PDO regulations or internal quality schemes. Cheese quality characteristics should be improved by studying the strong relation between product’s properties and process parameters and efficiency, in order to understand the critical phenomena that are involved in food processing. In this context, chemometric and computational tools are statistical approaches that can be applied to study these complex relations, in particular when many process parameters and product’s characteristics are evaluated at the same time, or to model food processing. Despite its high energy consumption, freezing of fresh dairy products can be a sustainable solution for supply chains: because of the improved storability and convenience, frozen products can be characterized by a lower impact on the carbon footprint if compared to fresh, refrigerated product; cconsidering long-distance markets, freezing can help to lower the costs of transport, by preferring the maritime transport instead of air transport, and can help to decrease waste by decreasing the amount of expired products to be withdrawn from the market. The feasability of high moisture cheese freezing and frozen storage can be valuable, but attention should be payed about process efficiency in terms of energetic costs, and product’s sensitivity in relation with the freezing process and frozen storage. Concerning dairy products regulated by European Protected Designation of Origin (PDO), dairies need fast and reliable methods to control their processes and to verify compliance with both legal limits or more severe internal quality programs. In the case of Parmigiano-Reggiano (P-R) cheese, grated P-R cheese accounted for 13.5% of the overall market of P-R cheese in 2017 and this percentage continuously increased in the last years. Grated P-R PDO cheese must comply with the maximum percentage of rind and particles having a diameter lower than 0.5 mm (<18% w/w and <25%, respectively), because an excessive amount of rind can have a negative impact on the sensory characteristics and product’s quality. The present thesis enabled to improve the knowledge about factors and phenomena that rule the behavior and the modification of fresh and long ripened cheeses during freezing and grating processes. Mathematical models were created to study Mozzarella cheese freezing process; thanks to a developed photogrammetric technique, it was possible to accurately reproduce Mozzarella cheese non-regular geometry and to accurately estimate freezing time and temperature profiles. Models highlighted the presence of temperature-surface differences related to the irregular geometry of the cheese that can also cause modification of the characteristics in the external layer. Moreover, freezing times were found to be strongly influenced by cheese shape variations. Mathematical freezing models can be valuable in industrial applications to predict freezing times and can be used to control and improve efficiency of Mozzarella cheese freezing process. Different freezing and thawing rates, that were experimentally modulated as a function of applied air temperature and velocity, did not cause significant modifications of Mozzarella cheese characteristics, as the freezing time was sufficiently short. On the contrary, the presence of covering liquid during freezing and thawing processes caused an absorption of water of Mozzarella cheese, that was found to be more viscous-like and humid than the fresh-one. Thus, freezing in the presence of covering liquid was a less suitable method to freeze Mozzarella cheese. Frozen storage of Mozzarella cheese slowed down but did not stop proteolytic reactions that showed a higher rate after thawing; oxidative reactions were also present. Moreover, frozen-stored cheeses showed a modification of water status from a molecular and a mesoscopic point of view, as a consequence of casein degradation and conformational change, that caused protein’s dehydration. Milk quality and cheese composition should be accurately controlled in order to limit the presence of proteolytic and lipolytic enzymes in the cheese, and to obtain good results after prolonged frozen storage. Moreover, a shorter shelf life period should be proposed for frozen-thawed cheese than the fresh one. Concerning grated P-R cheese, the grating behavior of different cheeses was found to be related to the textural properties of different zones of the wheel; in particular rind’s particles showed different particle size properties and in general were characterized by lower dimensions if compared to particles of the inner part of the cheese. According to these differences, it was possible to successfully predict particle size and rind percentage variations thanks to NIRs and IA measurements. These techniques can be successfully applied by dairies as internal quality control measurements to comply with both PDO regulation and quality programs.La globalizzazione dei mercati alimentari e la crescente domanda per alcuni formaggi Italiani tradizionali ed altamente deperibili, ha forzato il settore caseario ad investigare in nuovi metodi per aumentare l’export e/o per controllare la conformità con i disciplinari DOP o con programmi di controllo qualità interni. Le caratteristiche qualitative del formaggio dovrebbero essere migliorate studiando la forte relazione tra le proprietà del prodotto ed i parametri di processo e la sua efficienza, in modo da capire le criticità che sono osservabili durante la trasformazione dei prodotti. In questo contesto, gli strumenti chemiometrici e computazionali sono approcci che possono essere applicati per studiare queste complesse relazioni, in particolare quando molti parametri di processo e le caratteristiche del prodotto sono valutate contemporaneamente, o per modellare i processi alimentari. Nonostante l'elevato consumo energetico, il congelamento dei prodotti lattiero-caseari freschi può essere una soluzione sostenibile per le catene di approvvigionamento: grazie al miglioramento della conservabilità e della convenienza, i prodotti surgelati possono essere caratterizzati da un minore impatto ambientale rispetto al prodotto fresco e refrigerato; considerando i mercati a lunga percorrenza, il congelamento può contribuire a ridurre i costi di trasporto, preferendo il trasporto marittimo invece del trasporto aereo, e può contribuire a ridurre gli sprechi diminuendo la quantità di prodotti a fine shelf life da ritirare dal mercato. La potenzialità di congelare formaggi ad alto tenore di umidità ed il loro stoccaggio congelato può essere di grande valore, ma occorre prestare attenzione all'efficienza del processo in termini di costi energetici e alla sensibilità del prodotto in relazione al processo di congelamento e allo stoccaggio congelato. Per quanto riguarda i prodotti lattiero-caseari regolamentati dalla Denominazione europea di origine protetta (DOP), i caseifici hanno bisogno di metodi rapidi ed affidabili per controllare i loro processi e verificare il rispetto sia dei limiti legali che di programmi di qualità interna più severi. Nel caso del Parmigiano-Reggiano (P-R), nel 2017 il formaggio P-R grattugiato ha rappresentato il 13,5% del mercato complessivo del formaggio P-R e questa percentuale è aumentata continuamente negli ultimi anni. Il formaggio P-R grattugiato DOP deve rispettare la percentuale massima di crosta e particelle con un diametro inferiore a 0,5 mm (rispettivamente < 18% p/p e < 25%), poiché una quantità eccessiva di crosta può avere un impatto negativo sulle caratteristiche sensoriali e la qualità. Il presente lavoro di tesi ha permesso di migliorare la conoscenza dei fattori e dei fenomeni che regolano il comportamento e la modifica di formaggi freschi ed a lunga maturazione durante i processi di congelamento e grattugia. Sono stati creati modelli matematici per studiare il processo di congelamento del formaggio Mozzarella; grazie a una tecnica fotogrammetrica sviluppata, è stato possibile riprodurre con precisione la geometria non regolare del formaggio Mozzarella e stimare con precisione i profili di temperatura ed il tempo di congelamento. I modelli hanno evidenziato la presenza di differenze di temperatura sulla superficie, legate alla geometria irregolare del formaggio che può anche causare la modifica delle caratteristiche nello strato esterno. Inoltre, i tempi di congelamento sono stati trovati fortemente influenzati dalle variazioni di forma del formaggio. I modelli matematici di congelamento possono essere preziosi nelle applicazioni industriali per prevedere i tempi di congelamento e possono essere utili per controllare e migliorare l'efficienza del processo di congelamento del formaggio di Mozzarella. Diverse velocità di congelamento e scongelamento, che sono state modulate sperimentalmente in funzione della temperatura e della velocità dell'aria applicate, non hanno causato modifiche significative delle caratteristiche del formaggio Mozzarella, in quanto il tempo di congelamento era sufficientemente breve. Al contrario, la presenza di liquido di governo durante i processi di congelamento e scongelamento ha causato un assorbimento dell'acqua da parte del formaggio Mozzarella, che è risultato essere più viscoso e umido rispetto a quello fresco. Per questo motivo, il congelamento in presenza di liquido di governo è stato indicato come un metodo meno adatto per congelare il formaggio Mozzarella. Lo stoccaggio congelato di formaggio Mozzarella ha rallentato ma non ha fermato le reazioni proteolitiche che hanno mostrato un tasso più elevato dopo lo scongelamento; erano inoltre presenti anche reazioni ossidative. Inoltre, i formaggi congelati hanno mostrato una modifica dello stato dell'acqua da un punto di vista molecolare e mesoscopico, come conseguenza della degradazione della caseina e del cambiamento conformazionale, che ha causato la disidratazione delle proteine. La qualità del latte e la composizione del formaggio devono essere controllate con precisione al fine di limitare la presenza di enzimi proteolitici e lipolitici nel formaggio e per ottenere buoni risultati dopo un prolungato stoccaggio congelato. Inoltre, per il formaggio congelato dovrebbe essere considerato un periodo di durata di conservazione più breve rispetto al formaggio fresco. Per quanto riguarda il formaggio P-R grattugiato, il comportamento in grattugia di diversi formaggi è risultato essere correlato alle proprietà strutturali delle diverse zone della forma; in particolare le particelle di crosta mostravano diverse proprietà di particle size e in generale erano caratterizzate da dimensioni inferiori se confrontate con particelle della parte interna del formaggio. In base a queste differenze, è stato possibile prevedere con successo le variazioni percentuali delle dimensioni delle particelle e della crosta grazie alle misurazioni nel vicino infrarosso e di Image Analysis. Queste tecniche possono essere applicate con successo dai caseifici come misurazioni interne di controllo qualità per conformarsi sia al disciplinare DOP che ai programmi di qualità interni