Difuzivnost vode i toplinska svojstva dimljenog mekog sira

The main goal of the present study was to characterize the functional parameters of smoked soft cheese, with the emphasis on the behavior of water and milk fat, as analyzed by DSC, which was used to directly measure the melting/freezing phase transitions in the cheese. This study was complemented by NMR measurements of the organization and distribution of the aqueous phase within the emulsions constituting the cheese. The smoked and unsmoked cheeses were characterized by similar compositions in terms of protein (19.08-19.12 g∙100 g-1), fat (18.86-19.02 g∙100 g-1), and water content (59.86-60.27 g∙100 g-1). The water activity was higher in the unsmoked cheese (aw = 0.9736) than in the smoked cheese (aw = 0.9615). This result was confirmed by DSC (higher ice melting enthalpy) and NMR (higher T1 value) measurements. The smoking process led to differences in the distribution and binding of water to the lipid-protein matrix of the cheese. There was more non-freezed bound water in the smoked cheese which resulted in a more fragile and loosened structure in the smoked cheese than the unsmoked, which manifested in lower values of stretching and meltability. The meltability of the mozzarella smoked cheese was 1.5 times less than that of the unsmoked cheese (tube test and Schreiber test).Cilj istraživanja bio je utvrditi funkcionalna svojstva dimljenog mekog sira, s posebnim naglaskom na ponašanje vode i mliječne masti, ispitivanih pomoću metode diferencijalne termičke analize (DTA) koja je korištena za direktno određivanje faznih prijelaza taljenja i smrzavanja u siru. Navedeno istraživanje dopunjeno je primjenom NMR metode korištene za mjerenje raspodjele vodene faze unutar emulzija koje tvore sir. Dimljeni i nedimljeni sirevi imali su sličan sastav u smislu udjela proteina (19,08-19,12 g na 100 g), masti (18,86-19,02 g na 100 g) i vode (59,86-60,27 g na 100 g). Aktivnost vode bila je veća u nedimljenom siru (aw = 0,9736) u odnosu na dimljeni (aw = 0,9615). Ovaj je rezultat potvrđen DTA metodom (veće entalpije taljenja leda) kao i NMR mjerenjem (veće vrijednosti za T1). Proces dimljenja doveo je do razlika u raspodjeli vodene faze i vezanju vode za kompleks proteina i masti u siru. Dimljeni sir sadržavao je više nesmrznute vezane vode što se odrazilo kroz niže vrijednosti topljivosti i rastezljivosti sirnog tijesta. Stupanj topljivosti dimljenog mozzarella sira bio je 1,5 put manji u odnosu na nedimljeni sir (test tube i test Schreiber)

Influence of Seeds’ Age and Clarification of Cold-Pressed Raspberry (<i>Rubus idaeus</i> L.) Oil on the DSC Oxidative Stability and Phase Transition Profiles

After cold-pressing, small particles of seed residue remain in raspberry seed oil (RSO), even after passing it through cold filtration. The removal of the remaining seed residue is rather an alternative option to improve the visual properties of RSO. This study investigated the influence that the seeds’ age (0, 10, 20 months) and clarification process after pressing has on the oxidative stability and phase transition of RSO by means of differential scanning calorimetry (DSC). The results proved that the oil centrifugation process reduces the DPPH radical scavenging activity and oxidative stability measured by p-anisidine value (p-AnV) and DSC oxidation induction time (OIT) at 120 °C of all RSO samples, regardless of the age of the seeds (p ≤ 0.05). No significant differences were observed on the DSC melting and crystallization properties at 1 °C/min after the oil clarification by centrifugation (p > 0.05). The storage time of raspberry seeds, i.e., 10 and 20 months after expiry date, influenced the quality deterioration of RSO, as measured by higher p-AnV, lower DPPH, and OIT values (p ≤ 0.05). The results presented provide new information about oil production processing, suggesting that producers should reconsider giving up the clarification process of oil, since it lowers all quality parameters

Differential Scanning Calorimetry for Determining the Thermodynamic Properties of Selected Honeys

Thermodynamic properties of selected honeys: glass transition temperature (Tg), the change in specifi c heat capacity (ΔCp), and enthalpy (ΔH) were analysed using differential scanning calorimetry (DSC) in relation to the composition i.e. water and sugar content. Glass transition temperatures (Tg) of various types of honey differed significantly (p<0.05) and ranged from -49.7°C (polyfloral) to -34.8°C (sunflower). There was a strong correlation between the Tg values and the moisture content in honey (r = -0.94). The degree of crystallisation of the honey also influenced the Tg values. It has been shown that the presence or absence of sugar crystals influenced the glass transition temperature. For the decrystallised honeys, the Tg values were 6 to 11°C lower than for the crystallised honeys. The more crystallised a honey was, the greater the temperature difference was between the decrystallised and crystallized honey. In conclusion, to obtain reliable DSC results, it is crucial to measure the glass transition after the complete liquefaction of honey

Physicochemical Characteristics and Consumers’ Preferences for Milk Fat Products

The aim of this work is to analyse the physicochemical features of milk fat products (60%, 74% and 82% fat) and to learn about consumer preferences regarding these products, based on the results of consumer research. In addition, this study was conducted to answer the question of which features of milk fat products are most valued by consumers and which fat attribute has the strongest influence on consumer choice. Tests on the physicochemical characteristics of milk fat products, including analysis of composition, water activity, tocopherol and β-carotene content, colour, texture, melting profile and solid fat index, as well as consumer tests are carried out. The tested products met the requirements of Appendix II for Regulation (EU) No. 1308/2013. Based on consumer preferences, it was found that taste, followed by colour, was the most important attribute of milk fat products. The most desired fat was butter (82% fat), although it was difficult to spread at 4 °C. The best cuttability and spreadability was found in butter containing three-quarters fat (74%), but it was the least desired product by consumers. Most of the respondents (68%) preferred the yellow shade of milk fats to the white one. This indicates the need to add colours (e.g., carrot juice concentrate or other natural healthy food ingredients)

Discrimination of Selected Cold-Pressed and Refined Oils by Untargeted Profiling of Phase Transition Curves of Differential Scanning Calorimetry

The authenticity assessment of edible oils is crucial to reassure consumers of product compliance. In this study, a new approach was taken to combining untargeted profiling by using differential scanning calorimetry (DSC) with chemometric methods in order to distinguish cold-pressed oils (flaxseed, camelina, hempseed) from refined oils (rapeseed, sunflower, soybean). The whole spectrum of DSC melting profiles was considered as a fingerprint of each oil. Flaxseed and hempseed oils exhibited four endothermic peaks, while three peaks with one exothermic event were detected for camelina seed oil. In the case of refined oils, two endothermic peaks were detected for rapeseed oil, three for sunflower oil and four for soybean oil. Thermodynamic parameters, such as peak temperature, peak heat flow and enthalpy, differed for each type of oil. Principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used for processing data consisting of the whole spectrum of heat flow variables of melting phase transition. PCA demonstrated a clear separation between refined and cold-pressed oils as well as six individual oils. The OPLS-DA showed a distinct classification in six classes according to the types of oils. High OPLS-DA coefficients including R2X(cum)=0.971, R2(cum)=0.916 and Q2X(cum)=0.887 indicated good fitness of the model for oil discrimination. Variables influence on projection (VIP) plot indicated the most significant variables of the heat flow values detected at temperatures around −29°C, −32°C, −14°C, −10°C, −24°C and −41°C for the differentiation of oils. The study ultimately demonstrated great potential of the untargeted approach of using the whole melting DSC profile with chemometrics for the discrimination of cold-pressed and refined oils

Differential Scanning Calorimetry for Determining the Thermodynamic Properties of Selected Honeys

Thermodynamic properties of selected honeys: glass transition temperature (Tg), the change in specifi c heat capacity (ΔCp), and enthalpy (ΔH) were analysed using differential scanning calorimetry (DSC) in relation to the composition i.e. water and sugar content. Glass transition temperatures (Tg) of various types of honey differed significantly (p<0.05) and ranged from -49.7°C (polyfloral) to -34.8°C (sunflower). There was a strong correlation between the Tg values and the moisture content in honey (r = -0.94). The degree of crystallisation of the honey also influenced the Tg values. It has been shown that the presence or absence of sugar crystals influenced the glass transition temperature. For the decrystallised honeys, the Tg values were 6 to 11°C lower than for the crystallised honeys. The more crystallised a honey was, the greater the temperature difference was between the decrystallised and crystallized honey. In conclusion, to obtain reliable DSC results, it is crucial to measure the glass transition after the complete liquefaction of honey

Increasing the Oxidative Stability of the Wafer Lipid Fraction with Fruit Extract during Storage

Confectionary products are increasingly popular among consumers. However, since they usually have a long shelf life (about 12 months), their oxidative stability during long-term storage becomes a significant issue. Thus, the aim of this study was to investigate the effect of addition of commercially available fruit extract on the oxidative stability of lipid fraction, extracted from wafers sheets stored 13 months at 18 °C. For this purpose, the oxidation induction times (OIT) were determined by using isothermal differential scanning calorimetry (DSC). Conjugated diene content (CD) and 2,2-diphenyl-1-pikrylhydrazyl (DPPH) antioxidant activity were also monitored. All results obtained showed that the fruit extract addition slowed down effectively the peroxidation process of lipid fraction of wafer sheets. The rate of OIT and CD changes during the first six months of storage were about two times lower for the sample with the extract (LWE) than for the control (LWS). The DPPH antioxidant activity of LWE was higher than for the LWS sample until the 8th month of storage. It was stated that fruit extract effectively enhanced the oxidative stability of lipid fraction of wafers up until the 10th month of storage. After this period, CD values increased significantly for LWS and LWE samples, while at the same time there were no significant differences in OIT and DPPH values between both samples (p > 0.05)