Vlasta Piližota

Sterols and triterpene diols in olive oil as indicators of variety and degree of ripening

Sterols and triterpene diols in olive oil as indicators of variety and degree of ripening derived from three olive varieties and produced at three different harvesting periods were studied. In order to test the stability of the proposed indicators, oils obtained were stored for 12 months at three different temperatures. Thirty-six samples in total were subjected to GC analysis and results were processed by multivariate chemometric methods (MANOVA, PCA, and SLDA). Campesterol, β-sitosterol, Δ(7)-campesterol/Δ(5,24)-stigmastadienol, clerosterol, uvaol, and campestanol/Δ(7)-avenasterol were established as the indicators of variety of fresh oils, while when stored oils were included in the model, the final three compounds were substituted by 24-methylene-cholesterol/stigmasterol. The most important variables for differentiating fresh oils according to degree of ripening were Δ(7)-campesterol/β-sitosterol, uvaol/stigmasterol, clerosterol/Δ(5)-avenasterol and sitostanol/uvaol, while stored oils were differentiated by campestanol/stigmasterol, erythrodiol, stigmasterol/Δ(7)-campesterol, Δ(5)-avenasterol, 24-methylene-cholesterol/β-sitosterol and 24-methylene-cholesterol. Results demonstrated that sterols and triterpene diols can be used as indicators of variety and degree of ripening among virgin olive oils.

Prevention of thermal degradation of anthocyanins in blackberry juice with addition of different sugars Prevención de degradación termal de antocianinas en zumo de mora con adición de diferentes azúcares

The aim of this study was prevention of thermal degradation of blackberry juice anthocyanins through sugar addition. Blackberry juice samples were prepared without and with addition of 10% of different sugars (sucrose, fructose, glucose and trehalose), and heated at 50, 70 and 90 °C for 1 and 2 h. Since degradation of anthocyanins, over the time, followed first-order reaction model, calculation of the reaction rate constant (k), half-lives (t 1/2) and activation energy was conducted. During heating, at all investigated temperatures, degradation of anthocyanins occurred in higher or lesser extent. Addition of trehalose had the highest impact on anthocyanin stability during heating at all investigated temperatures and during both heating times. Samples with trehalose addition had the lowest k values thus the highest t 1/2 values at all investigated temperatures. In conclusion, careful formulation of foods, in our case sugar addition to blackberry juice, can minimise anthocyanins degradation during heating. El objetivo de este estudio fue la prevención de degradación termal de antocianinas de zumo de mora por la adición de azúcar. Se prepararon muestras de zumo de mora sin y con adición de 10% de diferentes azúcares (sacarosa, fructosa, glucosa y trehalosa) y se calentaron a 50, 70 y 90 °C durante 1 y 2 horas. Puesto que la degradación de antocianinas, durante el tiempo, siguió el modelo de reacción de primer orden, el cálculo de la constante de velocidad de reacción (k), semivida (t1/2) y energía de activación se llevó a cabo. Durante el calentamiento, en todas las temperaturas investigadas, la degradación de antocianinas sucedió en mayor o menor grado. La adición de trehalosa tuvo el mayor impacto en la estabilidad de antocianinas durante el calentamiento a todas las temperaturas investigadas y durante los dos tiempos de calentamiento. Las muestras con adición de trehalosa tuvieron unos valores k más bajos así como los mayors valores t1/2 a todas las temperaturas investigadas. En conclusión, la formulación cuidadosa de comidas, en nuestro caso adición de azúcar a zumo de mora, puede minimizar la degradación de antocianinas durante el calentamiento.

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.

Fruits and Vegetables (including Herbs)

Fruits, vegetables and herbs are agricultural products that could be contaminated with biological, chemical or physical hazards. Contamination could occur in the growing environment, after harvest, during preparation for storage and processing, in shipping to the market, in food service establishments, and/or in the home. The increasing number of produce-related outbreaks in industrialized countries has raised awareness to interventions that remove human pathogens from fresh produce. However, contamination of produce has always been a concern in the developing regions of the world which lack basic sanitary conditions. Chlorinated water has been widely used to sanitize fresh produce, but not enough to ensure the microbial safety of produce. The efficacy of several other chemical agents has been evaluated as potential alternatives to chlorine. Also, alternatives or modified methods have been also proposed such as MAP, irradiation, pulsed energy processing, etc.; however, none have yet gained widespread acceptance by the industry. To date the most important measures to ensure safety of fruits and vegetables remains prevention of contamination through the application of systems such as GAP.

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.

Volatile profile of sour cherry puree as affected by sucrose and trehalose

ABSTRACT In this study, effect of sugars (sucrose and trehalose) and their amount on the volatile profile of sour cherry puree was evaluated. Results were compared to sour cherry puree without addition of sugars. Volatiles amount depended on type and amount of sugar. This indicated that the sugars showed an effect on flavour profile. Volatiles with the ethereal, alcoholic flavour note were present in the highest amount in the puree while with the addition of sugars, amount of those volatiles was lower. Sweet, floral volatiles were determined in higher amount when sugars were added in comparison to puree. Addition of sucrose did not have significant impact on the volatiles with sweet flavour note, while with addition of trehalose lower amount of those compounds were determined than in puree. Sweet, fruity and fresh, green volatiles were determined in higher amount in samples with the addition of sugars, especially when trehalose was added. Addition of sugar did not have impact on pungent volatiles.

Phenolics content and antioxidant activity of sour cherry extracts with sugar addition

Sour cherry puree was prepared with addition of sucrose or trehalose (5% and 10%). After stabilization of the mixture (puree with sugars), extracts were prepared and contents of phenolics and anthocyanin, polymeric colour percentage, and antioxidant activity were determined. Extracts were stored for 65 days at 4 °C. Control sample was extract of sour cherry puree without sugars. After extraction, extracts with 10% of sucrose or trehalose had higher phenolic content than the control sample. Anthocyanin content was higher in extracts with trehalose addition. During storage of extracts, samples with trehalose had higher retention of phenolic and anthocyanins than other samples. Addition of sucrose and trehalose as well as their amounts affected the stabilities of phenolics, anthocyanins, and antioxidant activity in sour cherry extracts.

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).

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.