Calorimetry and thermal analysis in food science : an updated review

Food science is a domain of life science. Applications of thermal analysis and calorimetry (TAC) to food products deal with many investigation targets spanning from the characterization of the systems at molecular and supramolecular level to the description of the microbial metabolism. Food products are multi-phase and multi-component metastable systems where several processes can occur simultaneously during the preparation process and the shelf life. One therefore has to disentangle various contributions to the overall instrumental outputs, using appropriate data treatments and kinetic models, and/or results from other experimental approaches. The paper reports an updated survey of TAC applications to food products through specific examples of data treatments

Dissecting the effects of free fatty acids on the thermodynamic stability of complex model membranes mimicking insulin secretory granules

A stepwise micro-DSC study of Small, Large and Giant Unilamellar Vesicles prepared as pure and mixed systems of DMPC, DPPC, DSPC and DOPC was performed, achieving the preparation of final model membranes whose phospholipid compositions represent the 75% in terms of the phospholipids tails and the 50% headgroups of the Insulin Secretory Granules (vesicles located in the pancreatic Langerhans \u3b2-cells and which are responsible for insulin and amylin storage and secretion in response to nutrient intake). Moreover, the effect of Free Fatty Acids, whose levels are recurrently altered in diabetic and/or obese subjects, on the thermodynamic stability of the final membranes was eventually investigated. The results allowed to discriminate each single thermodynamic contribution among the main factors that dictate the overall thermodynamic stability of these complex unilamellar systems evidencing mainly entropic effects hierarchically summarized as phospholipid unsaturations > phospholipid tail length > membrane curvature. The effect of the Free Fatty Acids highlighted a strong stabilizing effect on the membranes as well as more pronounced phase segregations in the case of saturated acids (palmitic and stearic), whereas the opposite effect was observed in the case of an unsaturated one (oleic)

Water activity in biological systems. A review

Water deserves a major attention by researchers dealing with biological systems and related materials, like food, since it is ubiquitous and can be used like a \u201cnative\u201d probe to garner information about the hosting system, provided it may be freely displaced across. Its thermodynamic potential, namely, the water activity, aW, is related to that of the other compounds of the system considered via the Gibbs-Duhem relationship refl ecting the extent of the residual availability of water to solvate further solutes and sustain the molecular mobility of the bio-polymeric compounds. As for the experimental approaches to aW, this short review re-addresses the reader to other publications, while devotes a section to the Knudsen thermo-gravimetry that was used by the authors to determine the desorption isotherms of many food systems and related aqueous compounds. The paper remarks the importance of a preliminary assessment of water mobility and recalls the concept of \u201ccritical aW\u201c that takes into account the reduced mobility of water molecules in the vicinity of the glass transition. This opens the question of the reliability of sorption isotherms which encompass a wide aW range and the interpretation of the observed adsorption/desorption hysteresis. The multi-phase character of many biological systems is another issue of interest related to the reliability of the experimental approaches to aW. As examples of the role of aW on the stability of bio-systems and on the practice of a technological treatment, protein unfolding and osmo-dehydration of fruit pulps are reported

Thermal analysis on parchments II: Micro-DSC approach to assess and rank heat damages at a molecular level

New and artificially aged calf parchments by heat stress were investigated through the application of micro-DSC on samples of finely minced parchment suspensions in buffered environments. Criteria were assessed to define a unique normalized damage index (D.I.) parameter that aims at ranking, in a range from 0 to 1, the heat damage experienced by parchment collagen at a molecular level, and that is suitable for a direct application to historical parchments. The results indicate that such a calorimetric methodology is more sensitive in revealing damages deriving from mild heat stress than the analogous damage index previously proposed by the use of a DSC-TGA approach on parchments as-is. Synthetizing the overall injury extent in a unique numerical parameter represents a useful tool for ranking parchment conditions through simple calorimetric methods to help screening procedures and preservation strategies of such cultural heritage handcrafts

Isothermal calorimetry protocols to monitor the shelf life and aftermarket follow-up of fresh cut vegetables

Protocols and guidelines were assessed in order to apply isothermal calorimetry as a complementary/alternative method to monitoring, during the shelf life and the microbial growth/metabolism in commercial fresh cut vegetables with random initial microbial population. Moreover, the endogenous microbial population was used as a biosensor to check the modifications occurred during long storage for aftermarket characterization in the frame of vegetable waste treatments. Validation was obtained following ready-to-use carrots highlighting the effects of the different exposed surfaces (cylinders, sticks and a`-la-julienne cut) on the overall spoiling process during shelf life and green salad stored up to 14 days with regard to the aftermarket characterization

Thermogenic flux induced by lignoceric acid in peroxisomes isolated from HepG2 cells and from X- adrenoleukodystrophy and control fibroblasts

This work analyzes the thermogenic flux induced by the very long-chain fatty acid (VLCFA) lignoceric acid (C24:0) in isolated peroxisomes. Specific metabolic alterations of peroxisomes are related to a variety of disorders, the most frequent one being the neurodegenerative inherited disease X-linked adrenoleukodystrophy (X-ALD). A peroxisomal transport protein is mutated in this disorder. Due to reduced catabolism and enhanced fatty acid elongation, VLCFA accumulate in plasma and in all tissues, contributing to the clinical manifestations of this disorder. During peroxisomal metabolism, heat is produced but it is considered lost. Instead, it is a form of energy that could play a role in molecular mechanisms of this pathology and other neurodegenerative disorders. The thermogenic flux induced by lignoceric acid (C24:0) was estimated by isothermal titration calorimetry in peroxisomes isolated from HepG2 cells and from fibroblasts obtained from X-linked adrenoleukodystrophy patients and healthy subjects. Heat flux induced by lignoceric acid in HepG2 peroxisomes was exothermic, indicating normal peroxisomal metabolism. In X-ALD peroxisomes the heat flux was endothermic, indicating the requirement of heat/energy, possibly for cellular metabolism. In fibroblasts from healthy subjects the effect was less pronounced than in HepG2, a kind of cell known to have greater FA metabolism than fibroblasts. Our hypothesis is that heat is not lost but it could act a s an activator, for example on the heat-sensitive pathway related to TRVP2 receptors. To investigate this hypothesis we focused on peroxisomal metabolism, considering that impaired heat generation could contribute to the development of peroxisomal neurodegenerative disorders

Risk stratification of Barrett's oesophagus using a non-endoscopic sampling method coupled with a biomarker panel: a cohort study

Background Barrett's oesophagus predisposes to adenocarcinoma. However, most patients with Barrett's oesophagus will not progress and endoscopic surveillance is invasive, expensive, and fraught by issues of sampling bias and the subjective assessment of dysplasia. We investigated whether a non-endoscopic device, the Cytosponge, could be coupled with clinical and molecular biomarkers to identify a group of patients with low risk of progression suitable for non-endoscopic follow-up. Methods In this multicentre cohort study (BEST2), patients with Barrett's oesophagus underwent the Cytosponge test before their surveillance endoscopy. We collected clinical and demographic data and tested Cytosponge samples for a molecular biomarker panel including three protein biomarkers (P53, c-Myc, and Aurora kinase A), two methylation markers (MYOD1 and RUNX3), glandular atypia, and TP53 mutation status. We used a multivariable logistic regression model to compute the conditional probability of dysplasia status. We selected a simple model with high classification accuracy and applied it to an independent validation cohort. The BEST2 study is registered with ISRCTN, number 12730505. Findings The discovery cohort consisted of 468 patients with Barrett's oesophagus and intestinal metaplasia. Of these, 376 had no dysplasia and 22 had high-grade dysplasia or intramucosal adenocarcinoma. In the discovery cohort, a model with high classification accuracy consisted of glandular atypia, P53 abnormality, and Aurora kinase A positivity, and the interaction of age, waist-to-hip ratio, and length of the Barrett's oesophagus segment. 162 (35%) of 468 of patients fell into the low-risk category and the probability of being a true non-dysplastic patient was 100% (99% CI 96–100) and the probability of having high-grade dysplasia or intramucosal adenocarcinoma was 0% (0–4). 238 (51%) of participants were classified as of moderate risk; the probability of having high-grade dysplasia was 14% (9–21). 58 (12%) of participants were classified as high-risk; the probability of having non-dysplastic endoscopic biopsies was 13% (5–27), whereas the probability of having high-grade dysplasia or intramucosal adenocarcinoma was 87% (73–95). In the validation cohort (65 patients), 51 were non-dysplastic and 14 had high-grade dysplasia. In this cohort, 25 (38%) of 65 patients were classified as being low-risk, and the probability of being non-dysplastic was 96·0% (99% CI 73·80–99·99). The moderate-risk group comprised 27 non-dysplastic and eight high-grade dysplasia cases, whereas the high-risk group (8% of the cohort) had no non-dysplastic cases and five patients with high-grade dysplasia. Interpretation A combination of biomarker assays from a single Cytosponge sample can be used to determine a group of patients at low risk of progression, for whom endoscopy could be avoided. This strategy could help to avoid overdiagnosis and overtreatment in patients with Barrett's oesophagus. Funding Cancer Research UK

Influence of carob flour ingredients on wheat-based systems

Carob flour and its main constituents have been shown to possess nutritional benefits and might be considered as low-cost competitor to other food ingredients in enriched food products. In this study, we performed a DSC characterization of the thermal properties of carob flour and derived fractions (carob protein fraction and locust bean gum) at various moisture percentages, aiming at understanding their behaviour in more complex matrices. Furthermore, wheat/carob ingredient blends were investigated at different moisture content and components ratios to asses and dissect the interplay between carob and wheat flour macromolecules following their thermal transitions. The results indicated that only the carob protein fraction is adequate as ingredient for enriched wheat-based baking products since it does not significantly influence the water partition between the starchy and protein phases. Such a prediction was confirmed by technological trials, i.e., by preparing and comparing reference wheat loafs and ones enriched with 5% w/w of carob protein

Knudsen thermogravimetry approach to the thermodynamics of aqueous solutions

The use of isothermal TGA with Knudsen-like cells allows determination ofthe thermodynamic activity of water, aW. The typical experiment implies aslow dehydration ofthe aqueous solution atconstant temperature in dynamic vacuum conditions.The method isalternative to the classical isopiestic approach and offers the advantage ofacontinuous record onincreasing the solute concentration.These data can be directly treated according tothe classical thermodynamic relationships drawn from the Gibbs\u2013Duhem expression to evaluate the activity and osmotic coefficientofthe aqueous solutions ofelectrolytes and non-electrolytes, and,inthe case ofelectrolytes,allow determination ofsolubility ofthe solute.Discrepancies with respect to the literature data are observed when the viscosity ofthe systems becomes too high, asinthe case ofsugars with avery large solubility.Such amismatch may however beaccounted for either slowing the dehydration rate with use ofanarrower Knudsen orifice,orcorrecting the experimental aW with a calibration curve. The same approach can beapp lied tonon-aqueous solutions

Metabolic risk of new food technologies: calorimetric study of model cell membranes for the determination of the influence of free fatty acids (FFA) in diabetes mellitus onset

Type 2 diabetes mellitus (T2DM) is a chronic disease that continues to spread in both developed and developing countries. Indeed, the individuals affected by diabetes mellitus (type 1 and type 2) in the world are now close to 400 million and estimates suggest that they will reach 600 million by 2035. The rapid spreading of this disorder is influenced not only by genetic factors but also by environmental ones: socio-economic variations, evolution of lifestyle and changes in dietary habits have contributed to increase the percentage of overweight and obese individuals, which in turn have led to a greater diffusion of diabetes. In fact, weight gain is closely related to insulin-resistance onset, which is considered as the starting point for the development of the disease. However, the manner in which obesity and nutrition factors are linked to the onset of T2DM is not fully understood yet, especially at a molecular level. The aim of the project presented here is to prepare and characterize (thermodynamically and spectroscopically) model membranes which simulate as possible the phospholipid bilayers of the Langerhans \u3b2-cells in order to highlight and discriminate the role of the lipid composition and foodborne stress (in terms of [Ca2+] and [FFA]) in the membrane stability. Moreover, the interaction between the model membrane and hIAPP, which seems to be involved in \u3b2-cells death, will be used to evaluate the influence of membrane stability on T2DM onset