Ante Lončarić

Volatile compounds of freeze-dried sour cherry puree affected by the addition of sugars

ABSTRACT The aim of this work was to determine the influence of the addition (5, 10, or 20 g/100 g) of different sugars (sucrose, maltose, or trehalose) prior to freeze-drying on the key volatile compounds of the sour cherry puree. The key volatile compounds of sour cherries were benzaldehyde, benzyl alcohol, and 2-hexenal. The results obtained for the samples with the addition of sugars were compared to the control sample, the sample without sugar addition. The control sample contained 3.92 mg/kg of benzyl alcohol, 856.61 µg/kg of benzaldehyde, and 15.58 µg/kg of 2-hexenal. Benzaldehyde, the compound described as the typical cherry volatile compound, was determined in the highest amount in the sample with the addition of 10 g/100 g of trehalose (937.51 µg/kg). The highest amount of 2-hexenal was determined in samples with the addition of 10 or 20 g/100 g of trehalose (17.45 and 18.96 µg/kg, respectively). All samples with the sugar addition had lower content of the benzyl alcohol than the control sample. Generally, samples with the addition of sucrose had the lowest amount of examined volatile compounds.

Influence of phenol and sugar interactions on antioxidant activity of pomegranate juice

Nowadays, people are focusing on antioxidant-rich food due to its beneficial effect on health. Thus, the goal of this study was to investigate the interactions between catechin, quercetin, and gallic acid in the presence of sugars (sucrose and trehalose) in complex food matrix such as pomegranate juice. Antioxidant activity (AOA) was measured by three different methods, DPPH and ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP). In this paper, fundamental differences among used AOA measuring methods were confirmed, which can be traced back to interactions occurring between phenols and/or sugars. Even though addition of individual phenols increased AOA of mixtures, in the majority of binary and ternary mixtures antagonistic effects were observed. Positive effect of sugar addition was more pronounced in binary mixtures but the results were highly dependent on used AOA method.

Improving the quality of apple purée

The aim of the present study was to evaluate the effect of addition of 5% of apple peel powder (APP) and sugars (1, 5% of glucose, fructose, sucrose or trehalose) in apple purée on its phenolic composition and antioxidant activity (AOA). Apple purée samples were processed by freezing and freeze-drying. Apple purées containing APP showed higher phenolics, and AOA than the purées without APP. In freeze–dried samples the highest retention of individual polyphenols was achieved with addition of 1% of fructose or trehalose. However, in frozen samples the best impact on polyphenol retention had 5% of sucrose or trehalose. The results from this study showed the antioxidant potential of apple peel as a naturally-sourced antioxidants as well as a new insight into phenol–sugar interaction. These new findings could be of interest for the development of new food products rich in antioxidants which can improve human health.

Effect of baking and steaming on physicochemical and thermal properties of sweet potato puree preserved by freezing and freeze-drying

Thermal treatments could be one of the hurdles in applications of sweet potato purees for food different products formulation. Sweet potato purees (SPP) were prepared from raw, baked and steamed roots and they were preserved by freezing and freeze-drying. The effects of baking and steaming on thermal properties (melting temperature-Tm, melting transition energy - ΔH, and glass transition temperatures - Tg) of sweet potato (cultivar Beauregard), were measured by means of a Differential scanning calorimetry (DSC). The SPP made from baked roots had higher total and soluble solids (20.32 and 18.95%, respectively) than SPP made from raw and steamed roots. It can be also noticed that starch content was reduced by steaming and baking which reflected on amount of total and reducing sugars. The increase of reducing sugars level in baked SPP for 3.78% and steamed for 0.86% SPP was the result of yielding the maltose. The chemical changes of SPP also influenced the thermal behavior such that SPP prepared from baked sweet potato roots had the lowest initial freezing point (-2.80 °C) followed by SPP prepared from steamed (-2.63 °C) and raw (-0.71 °C) roots. The highest energy for melting (transition) was needed for SPP prepared from raw potato roots followed by steamed and baked roots, -103.79, -103.63, and -102.90 J/g, respectively. The glass transition in freeze-dried SPP prepared from raw roots was not detected. However, in the freeze-dried SPP prepared from baked and steamed roots the glass transition was detected in the range of 39 and 42 °C but with no significant difference (p>0.05).

Influence of disaccharides and pectin addition on antioxidant activity of phenolics

Food systems are very complex matrix and interactions between components have high impact on antioxidant activity of phenolic compounds. The aim of this study was to evaluate influence of addition of disaccharides, sucrose (S) and trehalose (T) or/and pectin (P) on antioxidant activity of catechin (C) or/and quercetin (Q) model systems after preparation and during storage at room temperature. Antioxidant activity (AA) was determined by DPPH, ABTS and FRAP method. Those methods have different mechanism of action thus different results were obtained. AA determined by DPPH method was higher in systems of C or Q when sugars or pectin was added than in systems of pure phenolics. In system CQ synergistic effect was observed, also when sugars or/and pectin was added the same effect was observed. During storage C system had the same AA, while Q system had lower AA. Systems C, Q and CQ with addition of sugars had higher AA. In systems with pectin addition in all combinations, higher AA was determined, except in the case of trehalose addition where very low AA was determined. AA determined by ABTS method in C systems with sugars or pectin decrease and increase in the case of Q system occurred in comparison to pure phenolics system. During storage, AA in systems C decreased while in systems Q increased. Systems CQ with pectin AA decreased while with sugars addition AA increased. AA determined by FRAP method was lower in systems of C or Q when sugars were added, and no synergistic effect was observed in system CQ. With addition of pectin, lower AA values were determined in all combinations. During storage, systems of C or Q and with sugars addition had lower AA. When pectin was added, C system had the same AA, and Q system higher. All combinations had lower AA. The results of our study showed the importance of food matrix composition as well as interactions that can occur between them.Ganoderma lucidum (GL) is a mushroom used as a traditional remedy for the treatment of various infections since ancient times. This study, was aimed to investigate antimicrobial activity potential of GL against Staphylococcus aureus, Enterococcus faecalis, Listeria monocytogenes, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, Candida glabrata, Candida krusei, and Candida parapsilopsis. Furthermore, it was also aimed to evaluate the toxicity potential of GL. Antimicrobial activities were screened by using microbroth dilution method. With regard to toxicity studies, cytotoxicity was evaluated by using XTT method against NIH3T3 cell lines, whereas genotoxicity study was conducted by Ames MPF 98/100 mutagenicity assay. Obtained data indicated that minimal inhibitory concentration values of the extract against the tested microorganisms ranged from 200 to 400μg/ml. No cytotoxic activity was observed related to the Ganoderma lucidum administrations. However, results of the Ames test pointed out a genetic damage with metabolic activation against TA98. At the highest concentration (5mg/ml) the extract showed 2.71 fold increase over the baseline significantly. (p<0.05). In conclusion, in spite of significant antimicrobial effect potential, Ganoderma lucidum should be used carefully because of its genotoxicity potential.

Effect of apple by-product as a supplement on antioxidant activity and quality parameters of pasta

Summary In this study, pasta was prepared by replacement of durum semolina (DS) with 10% and 15% of apple peel powder (APP). The control sample was pasta made from 100% DS. Total phenolic content (TPC), antioxidant capacity (AOA) and quality parameters of pasta were determined before and after cooking. Extraction of phenolics with methanol and ethanol, assisted with ultrasound (15 min) and by stirring (with magnetic stirrer for 1 h) was also compared. Results showed that addition of APP increased cooking loss and the amount of absorbed water of the pasta samples. Hardness and adhesiveness of pasta samples was decreased with APP addition. Pasta with added APP had significant higher levels of TPC and AOA compared with pasta without addition of APP. The highest TPC (1.4 g of gallic acid equivalents/kg) was in raw pasta with addition of 15% APP from which phenolics were extracted with ultrasound assisted extraction and methanol. Regarding AOA, the highest antioxidant activity (0.8 mg gallic acid equivalents/100g) was also in raw pasta with 15% APP, from which phenolics were extracted by stirring and ethanol. In cooked pasta, the levels of TPC and AOA, were significantly lower compared to raw pasta (p≤0.05). Sensory evaluation showed that there was no significant difference between DS and DS + 10% APP. Apple peel powder (APP) could be a food by-product, conveniently used as additive, for delivering health-promoting bioactive compounds such as polyphenols.