Ivelina N . Deseva

Fruits contain a number of useful substances including antioxidants. Their bio-accessibility after passing through the digestive tract is of primary importance when considering their benefits. In this respect, we investigated the effect of in vitro digestion on the phyto-chemicals of eight fruit juices. Freshly prepared juices from pomegranate, orange and grapefruit were used as well as commercially available juices from cherry, black grapes and aloe vera, blackberry and chokeberry, and two types of chokeberry and raspberries. Spectrophotometric and HPLC methods were used in order to analyse the sugar content, the total phenolic (TPC) and flavonoid contents (TFC), anthocyanins, phenolic acids and antioxidant activity. Principle component analysis was used to explain the differentiation among the types of fruit juice. Sugar recovery variation was between 4%-41%. The bio-accessibility of TPC ranged from 13.52%-26.49% and of flavonoids between 24.25%-67.00%. The pomegranate juice and the juice of black grapes and aloe vera kept 58.12 and 50.36% of their initial anthocyanins content, while for the other samples less than 1.10% was established. As a result, а maximum of 30% remaining antioxidant activity was measured for some of the samples, but for most this was less than 10%. In conclusion, fruit juices are a rich source of biologically active substances, but a more detailed analysis of food transformation during digestion is needed.

The aim of the current research is to investigate the effects of edible coatings based on celery pectin singly and in combination with a bacteriocin of Bacillus methylotrophicus BM47 on the quality and storage life of fresh blackberries under refrigeration conditions. In this study three experimental groups were prepared: uncoated blackberries as a control, blackberries with 1% pectin coatings and blackberries with 1% pectin coatings+bacteriocin of B. methylotrophicus BM47. During the storage at 4°C and 75% RH for 16 days, the weight loss, decay percentage, total soluble solids (TSS), titratable acidity (TA), pH, organic acids, sugars, total phenolic content, total anthocyanins and antioxidant activity were analyzed.


The results showed that the application of pectin and pectin+bacteriocin coatings led to a reduction in weight loss with 6.3% and 6.7% compared to the control fruit on the 16-th day of storage. A decrease in decay percentage was also noticed, which was most pronounced in the pectin+bacteriocin coated fruit compared to the pectin coatings and control. The pectin and pectin+bacteriocin coatings reduced TSS levels with 0.4%  and 0.6%, respectively compared to the control on the 16-th day of the storage, but did not affect TA and pH values. The pectin and  pectin+bacteriocin  coatings had no effect on decreasing total phenolic and anthocyanin contents or the concentration of sugars  (glucose and fructose) in both treatments and the control fruit. The pectin and pectin+bacteriocin edible coatings exhibited a protective effect on the ascorbic acid content, maintaining concentrations of 57.5 mg/100 g of fw and 58.8 mg/100 g of fw (day 16), which were close to the initial values. The pectin and  pectin+bacteriocin  treatments had also a  positive impact on antioxidant activity in the coated blackberries.  Both edible coatings effectively inhibited its decrease with the prolongation of the storage time and kept antioxidant levels of  231.8  TE/100  g  of fw and  232.4  TE/100  g  of fw  (day  16)  that were close to the initial values.

The rich world of herbs, with thousands of varieties and species, exhibiting multiple biological effects, including antioxidant activity, demands extensive studies. Melissa officinalis L., a representative of the Lamiaceae family, is a well-known herb that has long been used in traditional medicine to treat many disorders, and multiple studies have been conducted to identify its healing properties. The essential oil obtained by microdistillation of aerial parts of Melissa officinalis L. (Bulgarian origin) was analyzed by GC and GC-MS. Thirty-seven compounds were identified, representing 92.27 % of the total oil. The major components were terpenes with citronellal-18.45 %, and geraniol-15.22 % as the dominant representatives. Two water extracts were prepared to evaluate the radical-scavenging ability of M. officinalis-decoction and infusion. The antioxidant activity was determined using four spectrophotometric methods (ABTS, DPPH, FRAP, and CUPRAC). The TEAC values of the herb ranged from 389.52±3.11 μM TE/g DW (DPPH-infusion) to 1228.71±46.07 μM TE/g DW (CUPRAC-decoction). A significant correlation between the total phenolic content and the antioxidant activity was also determined. All obtained results revealed M. officinalis as a potential source of natural antioxidants.

The effect of temperature and time of cultivation of thermophilic actinomycete isolate 11A on proteolitic activity was investigated and modeled by using a central composite design (CCD). The two independent variables (temperature and time of cultivation) were studied at three levels with 4 repetitions at the central point totaling of 48 experimental runs. From the analysis of the results was determined that the temperature of cultivation has the greatest effect on the protease production of the isolate. The most favorable conditions for the enzyme production were determined from the obtained regression model. The results were compared with a previous study in which a systematic investigation of the operating parameters was carried out.

Two proteases (H1BT and H2BT) were obtained from actinomycete strain, isolated from Antarctic penguin excrements. In order to investigate their stability, the partially purified enzymes were subjected to UV light irradiation for up to 5 hours. Wavelength of 302 nm was used with a nominal power of 8 W. Antioxidant supplements such as dithiothreitol (DTT) and cysteine were used in order to protect the enzymes from inactivation. The protease H1BT kept more than 50% of its initial activity after 30 min of irradiation without any supplements and dropped down to 29% afterwards. The protease H2BT was stable for up to 10 min of irradiation and then lost more than 60% of its activity. Both DTT and cysteine enhanced the stability of the two proteases and thereafter they showed greater activity. In the presence of 5 mM DTT the residual activity of H1BT protease increased 1.54 times than its residual activity without supplements. For the same cysteine concentration the corresponding residual activity increased 1.18 times only. In the case of H2BT protease a similar trend was observed.

In this study we isolated and screened 58 thermophilic actinomycetes strains for proteolytic activity. The 11A
strain originally isolated from a soil sample collected from Antarctic areas that showed highest proteolytic activity
was chosen for further analyses. The accomplished observations on the microbial growth in continuous shake
flasks confirmed (he strain's thermophilic nature and identified its maximal protease synthesis at 45°C for 48h.
The pH profile for enzyme production was investigated as well. The observed pH range was from 6.5 to 8.5 and
the optimal value for the maximal enzyme synthesis was determined at pH 8.0. The influence of different
temperatures on the enzyme activity was observed for period of 2 days. The enzyme retained more than 90% from
its initial activity during incubation at 50°C for 48h. It was also found that the enzyme is relatively stable up to
80°C. The influence of different concentrations of carbon and nitrogen nutrient sources on the level of enzyme
production was also investigated.