Innovative Nutritional Aspects of locally produced Italian cheeses

Il formaggio sta dimostrando possedere, oltre alle caratteristiche nutrizionali classiche, degli aspetti nutrizionali innovati derivanti dalle proprietà di peptidi bioattivi contenuti nella frazione proteica caseinica del formaggio e rilasciati in seguito a proteolisi, ed ancora dalle proprietà di acidi grassi insaturi, quale l’acido linoleico coniugato. L’obiettivo di tale studio di dottorato è stato indagare su questi aspetti nutrizionali innovativi in formaggi tipici italiani quali Grana Padano e TrentinGrana, che pur essendo due formaggi molto simili tra loro, differiscono per l’uso della molecola antibatterica lisozima solo per la produzione del Grana Padano. Simulazioni in vitro della digestione gastrointestinale, nei campioni dei due formaggi a diversi tempi di stagionatura, ha dimostrato che esiste una relazione positiva tra tempo di stagionatura e digeribilità del calcio nel Grana Padano ,quando vengono considerati nella correlazione i risultati dei campioni con stagionatura superiore ai 24 mesi. A tempi di stagionatura inferiori a 24 mesi, i risultati di digeribilità del calcio del Grana Padano sono dispersi come appare nei campioni di TrentinGrana analizzati. Inoltre l’analisi RP-HPLC della distribuzione molecolare degli oligopeptidi dei campioni dei due formaggi, dimostra che la frazione peptidica coinvolta nel legame del calcio e quindi nel suo assorbimento, è quella compresa tra 1000 e 1500 D, e che l’analisi Seldi ha rilevato essere quella dei peptidi attivi fosfocaseinici. Inoltre differenze tra i due formaggi con e senza lisozima, appaiono solo per campioni tra 15 e 20 mesi di stagionatura, in cui campioni di formaggio senza lisozima appaiono più idrolizzati di quelli che lo contengono. Quindi dai risultati ottenuti appare che le differenze del profilo peptidico apportate dal lisozima non modificano le proprietà dei fosfopeptidi di assorbimento del calcio, forse influenzate da altri fattori che intervengono nella produzione del formaggio. L’attività ACE-inibitoria di abbassamento della pressione arteriosa esercitata da peptidi bioattivi è stata testata nei due formaggi, dimostrando che né il tempo di stagionatura e il grado di proteolisi, né il lisozima sono correlati all’attività ACE-inibitoria. Ed infine per l’importante ruolo che ha il minerale calcio nella dieta, indici di digeribilità del minerale in diversi alimenti sono stati considerati, in modo da poter formulare in maniera corretta diete alimentari coprendo il fabbisogno giornaliero con l’adeguato apporto energetico. I formaggi hanno dimostrato possedere indici di digeribilità del calcio superiori ad altri alimenti vegetali o a base di soia. In particolare il valore di digeribilità del Calcio del Grana Padano calcolato in vitro ha confermato il valore ottenuto in vivo , pari a 80%.This study aimed to investigate about the not common known nutritional aspects of cheeses, which derive from their chemical components. In fact, in addition to the supply of macronutrient, cheeses are gaining interest as a source of bioactive peptides, of conjugated linoleic acid or for the new insight in the metabolic role of calcium. In vitro simulation of human gastrointestinal digestion revealed that cheeses have an higher digestibility of calcium than other foods, because of their casein-derived bioactive phosphopetides (CPPs) content has the ability to carry calcium minerals and avoid calcium precipitation, making it available for intestinal absorption. The in vitro calcium digestibility was calculated for different foods- cheeses, soya based foods and vegetables- to correct cover calcium requirements with an equilibrate energy intake. Calcium digestibility was also assessed in different ripened time Italian locally produced, semi fat, hard cheeses, Grana Padano and TrentinGrana. The main difference between them is the use or not of lysozyme during manufacturing. In Grana Padano samples, produced using lysozyme, there is a positive relationship between aging and dCa (r2 = 0.27; P 24 months aged are considered (Grana Padano dCa results of samples less 24 months aged are quite widespread) , while in TrentinGrana, produced without the use of lysozyme, no significant correlation has been detected. RP-HPLC distribution analysis of oligopeptides molecular weight of these cheese showed that the only difference between them is that cheeses without lyzozyme, aged between 15 and 20 months, are more hydrolyzed than the same ripened time Grana Padano samples. Moreover the fraction of oligopeptides involved in calcium binding ranges between 1000 and 1500 D. SELDI analysis confirmed CPPs presence in this range. Therefore changes in cheese peptidic profiles probably caused by the use of lysozyme do not influence calcium digestibility because according to this study there is not a connection between change in peptidic profile and calcium digestibility results. The difference in calcium digestibility in Grana Padano samples aged over 24 month results should be probably ascribed also to the influence of other factors occurring during cheese manufacturing. Moreover, ACE-inhibitory activity of bioactive peptides was tested on in vitro digested Grana Padano and TrentinGrana samples with different ripening times. Correlation was not found between ACE-inhibitory activity and proteolysis level in different ripened time samples nor the lysozyme influence in releasing ACE-inhibitory bioactive peptides

Effect of lysozyme and ripening time on in vitro Ca digestibility of Grana Padano DOP cheese

Objectives High Ca content is one of the most important characteristic of dairy products, According to some Authors dairy products have a better Ca digestibility compared to plant foods and this characteristic has been related to the inclusion of Ca in the caseinophosphopeptides (CPP). Because ripening time and lysozyme can affect peptide pattern we decided to study the effect of these two factors on in vitro Ca digestibility. Experimental methods 20 samples of Grana Padano produced with lysozyme and 17 samples produced without lysozyme (total 37 samples), aged between 11 and 25 months were obtained from 2 different cheese-factories. In vitro Ca digestibility (dCa) was determined using the methods of Perales et al (J Agric Food Chem, 2005, 53: 3721). Molecular weight (MW) of peptides was determined by exclusion chromatography and CPP were determined by HPLC-MS. Analysis of variance was carried out with SAS 9.1 using GLM procedure of the SAS 9.1. The correlation between variables was performed with the PROC CORR of SAS 9.1. Results The dCa (%) at ripening time of 12, 15-20 and > 20 months were: 71.75, 76.10, 86.04 for Grana Padano and 73.21, 63.70, 62.59 for lysozyme-free cheese. In Grana Padano dCa and aging were positively related (r2 = 0.27; P<0.05). Since Ca is almost entirely associated with caseins, the difference in dCa could be due to a different proteolysis mediated by the presence of lysozyme as reported by Sforza et al. (Eur J Mass Spectrom, 2004, 10: 421). In the range of MW from 1000 to 2500 D, we observed an higher number of Ca-binding sequences in lysozyme containing cheese compared to Trentin Grana and this fact could explain the different result. Furthermore dCa in lysozyme containing cheese was positively correlated to the concentration of peptides having MW in the range 1000-1500 D and 1500-2500 D. Conclusions A larger number of cheese samples is necessary in order to better describe the effect of ripening and lysozyme addition on Ca digestibility, however our results suggest that the use of lysozyme in cheese-making can affect peptide pattern of cheese and dCa, this could be of nutritional relevance in people with high Ca requirement such as elderly people or pregnant women

In vivo and in vitro digestibility of the calcium contained in foods of animal and plant origin

The aim of this study was to assess Ca digestibility using in vitro and in vivo methodology (rats). The tested foods were: cheese (Grana Padano; Emmentaler), soybean-based products (tofu; burger; milk; yogurt), and legumes (peas; beans). Ca digestibility was found to be high in Emmentaler (84.3%), Grana Padano (83.6%) and tofu (80.3%), with significantly lower values for soya burgers (64.1%) and soya milk (60.6%). The lowest values were detected in peas (49.6%) and beans (31.4%). Poor correlation was found between in vivo and in vitro data. The current RDAs have been established on the basis of 30% Ca digestibility, a value which reduces the risk of calcium deficiency but underestimates the contribution of dairy products. The adoption of specific, instead of general, digestibility values for each food might improve the accuracy of dietary formulations. This will require considerable efforts to develop simple and reliable in vitro methods to assess foods