Arbutus unedo fruit syrup as a fortifying agent: effect on physicochemical, microbiological, rheological, sensory and antioxidant properties of yoghurt

This study aims to assess the antioxidant and the antibacterial activities of Arbutus unedo fruits and to valorize its syrup by the incorporation in bi-layer yoghurt. The antioxidant activity of the ethanol 80% fruits and syrup extracts was evaluated by three methods namely DPPH·, ABTS·+ and FRAP. The antibacterial activity was tested against seven pathogenic bacteria using agar well diffusion method. The yoghurt was prepared using 10 and 20% layers of A. unedo syrup, physicochemical, rheological, microbiological and sensorial characteristics and the antioxidant activity were investigated during cold storage. The results revealed that the heat treatment decreased the phenolic compounds contents and the antioxidant activity in the syrup extract. Both fruits and syrup extracts demonstrated an antibacterial activity against the tested bacteria. The highest inhibition diameter (40 mm) was recorded for Aeromonas hydrophila at 100 mg/mL of fruit echtanolic extract. The prepared bi-layer yoghurts showed stability for the physicochemical and microbiological properties during storage. The rheological properties revealed that the A. unedo syrup increases the yoghurt consistency (k). The antioxidant activity of the yoghurt indicated that fermentation improved the radical scavenging power of the A. unedo syrup at the beginning and the activity decreased slowly during storage.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05801-4.

Analysis of Minerals and Heavy Metals Using ICP-OES and FTIR Techniques in Two Red Seaweeds (Gymnogongrus griffithsiae and Asparagopsis taxiformis) from Tunisia

In this study, the mineral and heavy metals (arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), potassium (K), manganese (Mn), sodium (Na), phosphorus (P), and lead (Pb)) in two red Tunisian seaweeds Gymnogongrus griffithsiae (G. griffithsiae) and Asparagopsis taxiformis (A. taxiformis), were evaluated. Mineral and trace element analyses were achieved using inductively coupled plasma optical emission spectrometry (ICP-OES). Fourier transform infrared (FTIR) spectroscopy was used to predict the major functional groups that would be implicated in the seaweeds mineral uptake. Our results showed that the studied A. taxiformis species had much higher mineral and heavy metal concentrations than G. griffithsiae. Na (200.60 mg/kg) was the most abundant element followed by K (137.84 mg/kg) > P (35.93 mg/kg) for A. taxiformis species. However, only Na (165.23 mg/kg) and P (51.19 mg/kg) were detected in G. griffithsiae alga. As regards heavy and toxic metals, allowable concentrations have been found in both seaweeds. The concentration ranges for the most undesirable heavy metals were as follows: Pb (0.39-0.51 mg/kg), As (0.11-0.40 mg/kg), Cd (0.01-0.02 mg/kg), and Hg (0.00-0.02 mg/kg). According to FTIR analysis, the major functional groups present in the studied seaweeds were carboxyl, hydroxyl, sulfate, and phosphate groups that are considered as excellent binding sites for metal retention.

Drying methodology effect on the phenolic content, antioxidant activity of Myrtus communis L. leaves ethanol extracts and soybean oil oxidative stability

In this study, different drying methodologies (convective air, oven and microwave) of Myrtus communis L. (M. communis L.) leaves were conducted to investigate their effects on the levels of phenolic compounds, antioxidant capacity of ethanolic extracts (EEs) as well as the soybean oil oxidative stability. Drying methodology significantly influenced the extractability of phenolic compounds. Microwave drying led to an increase in the amounts of total phenols, flavonoids and proanthocyanidins followed by oven drying at 70 °C. Higher temperature of drying (100 and 120 °C) led to a significant reduction of their amounts (p < 0.05). An ultra-performance liquid chromatography method combined with high resolution mass spectroscopic detection was used to analyze the phenolic fraction of extracts. Higher amounts of the identified compounds were observed when leaves were heat treated. Furthermore, the evaluation of the antioxidant activity showed that the studied extracts possess in general high antioxidant capacities, significantly dependent on the employed drying methodology. The incorporation of the different extracts at 200 ppm in soybean oil showed that its oxidative stability was significantly improved. Extracts from leaves treated with microwave (EE_MW) and at 70 °C (EE_70) have better effect than BHT. The results of the present study suggest that microwave drying could be useful to enhance the extractability of phenolic compounds and the antioxidant capacity of M. communis L. leaf extract.

Physicochemical characterization of oil, antioxidant potential, and phenolic profile of seeds isolated from Tunisian pomegranate (Punica granatum L.) cultivars

Pomegranate (Punica granatum L.) seeds oils (PSO) from three Tunisian varieties namely Jebali, Testouri, and Gabsi were extracted by ultrasonic-assisted extraction and analyzed for their physicochemical properties, fatty acids (FA) profile, and sterol composition. PSO of Gabsi and Testouri showed the best quality indexes in terms of peroxide and acid values and the highest oxidative stability index was observed for PSO of Gabsi ecotype (2.534 hr). Polyphenol content of PSO of Gabsi ecotype (886.909 mg/kg) was roughly 3 and 23 times higher than that of Jebali and Testouri ecotypes, respectively. Twelve FAs were identified by GC/FID. Punicic acid was the major compounds ranged from 81.53% (Testouri) to 86.41% (Gabsi). The unsaturated/saturated FA ratios of PSO were 14.53, 15.95, and 18.68, respectively for Gabsi, Testouri, and Jebali, respectively. Phytosterols were also identified and β-sitosterol was the major compound in PSO. In addition, the phytochemical and antioxidant properties of phenolic extracts obtained from pomegranate seeds residues were investigated. Pomegranate seeds extract (PSE) of Gabsi cultivar showed the highest content of polyphenols (64.762 mg CAE/g) and flavonoids (7.127 mg RE/g). Antioxidant potential of extracts was performed using DPPH test and total antioxidant capacity (TAC). Results revealed that Gabsi cultivar was the most reactive extract with EC₅₀ of 0.105 mg/mL for DPPH test and 40.622 mg AA/g for TAC. Phenolic profiles of PSE were also investigated. Results showed the importance of cultivar selection in the potential use of bioactive compounds of seeds as nutraceutical ingredients in food and chemical industries. PRACTICAL APPLICATION: Three Tunisian pomegranate cultivars namely Jebali, Testouri, and Gabsi were investigated for their seeds oil and phenolic composition. Pomegranate seeds oil (PSO) are rich in bioactive polyunsaturated fatty acids and phytosterols that can be of interest in several food and chemical industrial applications. Moreover, pomegranate seeds extracts are a natural source of antioxidant components, such as phenolic compounds, that can be used by the pharmaceutical industry as promising nutraceutical ingredients. The obtained results can be used to provide guidance on cultivar selection during industrial applications.

Freeze-dried, oven-dried, and microencapsulation of essential oil from Allium sativum as potential preservative agents of minced meat

The present study was conducted to compare the antibacterial activity of oven-dried and freeze-dried Allium sativum along with its spray-dried microencapsulated essential oil in the preservation of minced beef meat. Allium sativum extracts were tested against mesophilic aerobic microorganisms, coagulase-positive staphylococci, Escherichia coli, Salmonella sp., and the sulfite-reducing anaerobes. A difference between the chemical compositions of powders obtained by the conventional oven-drying and freeze-drying has been verified by HPLC-MS2, freeze-dried fresh garlic powder contains 74% of allicin, and 12% cysteine sulfoxides comparing to the oven-drying garlic powder in which is detected two thiosulfinate isomers: allicin (67%) and allyl-1-propenyl thiosulfinate (21%). CIELAB color analysis was performed to assess the effect of drying temperature on powders. The microflora-inhibiting effect of freeze-dried fresh garlic and the spray-dried microencapsulated essential oil at a concentration of 20% represents a promising way to be used in food systems such as meat and meat products preservation, at 4-8°C.

Characterization of Polyphenolic Compounds Extracted from Different Varieties of Almond Hulls (Prunus dulcis L.)

Ultrasound-assisted extraction (UAE) was applied as a pretreatment technique to improve the recovery of polyphenols from the almond hulls of four Tunisian and three Italian almond varieties, followed by the characterization with HPLC-DAD. The operating parameters (solid/liquid ratio, extraction time, and ethanol concentrations) were optimized using a Response Surface Methodology. A polynomial equation was calculated to describe the relationship between the operating parameters and dependent variables as total polyphenolic content (TPC) and antioxidant activity (RSA). A desirability function approach was used to determine the optimum conditions for operating parameters: a solid:solvent ratio of 2 g/100 mL, an extraction time of 13 min, and an ethanol concentration of 51.2%. Among the almond varieties, Pizzuta and Fakhfekh showed the highest polyphenol content and antioxidant activity. HPLC-DAD analysis of almond hull extracts confirmed that chlorogenic acid, catechin, and protocatechuic acid were the most important polyphenols in almond hull. The results highlighted that UAE could be an effective technique for the recovery of phenolic compounds from almond hull, thereby making this byproduct a promising source of compounds with potential applications in food and healthcare sectors.

Separation and evaluation of natural antileishmanial potential against Leishmania major and infuntum isolated from the Tunisia strains

<p class="Abstract">Besides its nutritional value as a dietary supplement, Tribulus terrestris is used as a remedy for fertility disorder in Ayurveda and Chinese medicine as well as by modern herbalists. The aim of this study was to explore the biological potential (antileishmanial effect) of an extract rich in saponins from Tunisian tribulus. The chloroform extract of the various parts of T. terrestris was subjected to partial purification by solvent partitioning with ethanol and n-butanol. All prepared extracts were tested for their anti-leishmanial activity. The result showed that n-butanolic extract (saponin fraction, when isolated from leaves part) exhibited the best antileishmanial effect against both pathogenic parasites Leshmania L. major (GlC94) and L. infuntum (LV50) evaluated in vitro assessment through MTT assay. n-Butanolic extract had been detected, quantified and purified using the RP-HPLC finger print (Hypersil ODS coupled to UV-vis). High peak area (5116.82 at 3.03 min) was detected at 205 nm.</p>

PESTO SAUCE TYPE PRODUCTS: INFLUENCE OF BEESWAX AND STORAGE CONDITIONS ON RHEOLOGY AND COLLOIDAL STABILITY

One of the major problems for pesto sauce type products is the tendency of oil to cream, causing their alteration and decreasing consumer’s acceptability. In this study, colloidal and oxidative stability of pesto samples with (0.5-1.2%) of beeswax was evaluated during storage at 4, 20 and 40°C. The rheological behavior and color analysis was evaluated at the same temperatures. Sensory evaluation by using a hedonic test was also perfomed. Increasing the samples beeswax content increased the pesto colloidal stability. The samples with 0.8-1.2% have the highest stability and overall performed well on sensory analysis. The peroxide values of samples increased significantly (p

Chemical composition, antioxidant potential and phenolic profile of oil mill waste water from Tunisian olive varieties (Chetoui and Chemlali)

Oil mill waste water (OMWW) is of great interest due to the presence of valuable resources such as biophenols that can be recovered as food additives and pharmaceuticals. The aim of this study is to investigate the variation of physicochemical composition of OMWW from Chetoui and Chemlali varieties, to evaluate phenolic composition, antioxidant potential and phenolic profile of OMWW extracts under native and acidified conditions. Liquid-liquid extraction was performed for the extraction of polyphenols. Antioxidant activity was investigated by DPPH•, ABTS•+ and FRAP tests. Phenolic compounds content was determined by HPLC-DAD method. OMWW from Chetoui variety has been shown to contain an important amount of K, Ca and Na whereas Chemlali cultivar was rich in Mg. Phenolic extract from Chetoui fruit (COCt) has been  shown to contain the highest amount of polyphenols (2.48 ± 0.21 g L-1) as well as an appreciable content of flavonoids (9.39 ± 0.32 g L-1). However, phenolic extract from Chemlali fruit (COCm) has been shown to have the highest content of proanthocyanidins (0.39 ± 0.00 g L-1). Acidification treatment improved polyphenol recovery of extracts from both varieties. COCt was more active using DPPH (EC50 of 7.5 mg L-1) and FRAP tests. However, COCt and COCm exhibited the same activity using ABTS test. In general, acidification treatment decreased antioxidant activity of extracts. COCt has been shown to contain higher amount of hydroxytyrosol when compared to COCm (157.16 ± 0.820 and 23.440 ± 0.440 mg g-1 D.W. of extract, respectively) as revealed by HPLC-DAD analysis. 

Fibre concentrate from artichoke (Cynara scolymus L.) stem by-products: Characterization and application as a bakery product ingredient

The potential of fibre concentrate from artichoke stem by-product in bakery application was investigated. The elaboration of fibre concentrate was characterized by an extraction yield of 48.5%. The chemical composition showed high total dietary fibre (85 g/100 g d.m) and low lipid contents (0.5 g/100 g d.m). The fibre concentrate showed good water holding capacity (8.17 g/g) and high oil holding capacity (16.17 g/g). The effect of fibre concentrate incorporation to wheat dough, at level of 2%, on the rheological properties and physical characteristics of bread was also evaluated. The results showed that the addition of fibre concentrate in wheat flour significantly improved (P < 0.05) dough properties inducing an increase of water absorption, stability and tenacity, and a reduction of extensibility and softening in comparison to the dough without fibre. The colour values of the crust and crumb were significantly (P < 0.05) altered by the addition of fibre concentrate. It was also found that incorporation of fibre concentrate to bread produced a comparable specific volume and enhanced the shelf life, as textural studies revealed.

Effect of artichoke (Cynara scolymus L.) by-product on the quality and total phenol content of bread

Legume flours, due to their phenol and fibre content, are ideal ingredients for improving the nutritional value of bakery products. In this study, artichoke stem powder (ASP) was used to substitute 0%, 2.5%, 5%, 7.5% and 10% of wheat flour for making breads. Proximate composition of wheat flour and ASP were determined. Bread qualities and total phenols content were analyzed and compared with those of wheat bread. Results show that ASP contained 10.37% moisture, 10.28% ash, 11.53% protein, 0.86% fat, 51.29% fibre and 1350 mg EAG/100g d.m. ASP addition considerably modified the bread quality: altered appearance and texture, darker crumb and more intense odour were observed. From the sensory evaluation, tastes of bread with higher content of ASP (7.5 and 10%) were the most acceptable for assessors. Total phenol contents of breads significantly increased with the addition of ASP. Therefore ASP may be considered as valuable ingredients for industrial manufacture of functional foods.

Melanin and humic acid-like polymer complex from olive mill waste waters. Part I. Isolation and characterization

A water soluble humic acid and melanin-like polymer complex (OMWW-ASP) was isolated from olive mill waste waters (OMWW) by ammonium sulfate fractionation to be used as natural additive in food preparations. The dark polymer complex was further characterized by a variety of biochemical, physicochemical and spectroscopic techniques. OMWW-ASP is composed mainly of proteins associated with polyphenols and carbohydrates and the distribution of its relative molecular size was determined between about 5 and 190 kDa. SDS-PAGE shows the presence of a well separated protein band of 21.3 kDa and a low molecular weight peptide. The OMWW-ASP complex exhibits a monotonically increasing UV-Vis absorption spectrum and it contains stable radicals. Antioxidant activity measurements reveal the ability of the OMWW protein fraction to scavenge both the cationic 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+)) radical, as well as the stable nitroxide free radical 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOL).

Phytochemical and Biological Investigation of Two Diplotaxis Species Growing in Tunisia: D. virgata &amp; D. erucoides

A phytochemical investigation of Diplotaxis virgata D.C. and D. erucoides (L.) D.C. (Brassicaceae) offered to the isolation of two new flavonoids isorhamnetin-3-O-α-l-glucopyranoside (1) and rhamnetin-3,3'-di-O-β-d-glucopyranoside (2), respectively. Their structures have been elucidated from the extended spectroscopic methods, including 1D- and 2D-NMR, UV and mass spectrometry analysis and by comparison with literature data. The fatty acid composition of the hexane extracts of the two species was also investigated by using GC-MS. The antioxidant activity of ethanol, ethyl acetate, n-butanol extracts and the isolated compounds from the two species was evaluated using DPPH and ABTS⁺ scavenging assays. All the tested samples showed an efficient radical scavenging ability, with IC50 values ranging from 16-40 µg/mL for the DPPH and from 17-44 µg/mL for the ABTS⁺ assays. In addition, the antibacterial activity of the prepared extracts and compounds 1 and 2, determined by well diffusion agar method against two Gram positive and five Gram negative bacteria, was evaluated and the results showed significant effects against all strains used.

Improvement of the composition of Tunisian myrtle berries (Myrtus communis L.) alcohol extracts

Different extracts from myrtle berries were obtained using alcohol-water mixtures as an extraction medium in the range of 60-90% (v/v) to study the extraction efficiency in the preparation of myrtle liqueur. Flavonoids and anthocyanins were identified by high-performance liquid chromatography (HPLC) coupled with electrospray mass spectrometry and quantified during the maceration period by HPLC coupled with ultraviolet/visible detection. The antioxidant activity was tested by the 2,2-diphenyl-1-picrylhydrazyl assay. Dry matter, pH, and color parameters (L, a, b) were also analyzed. At the end of the maceration period, EE80 showed better anthocyanins stability and the highest total antioxidant activity (87.5%). These results suggest that the use of ethanol 80% provides the extract with the best characteristics for liqueur preparation. The present study contributes significantly to increase the marketing appeal of myrtle berries.

Occurrence of mycotoxin patulin in apple-based products marketed in Tunisia

An investigation on the presence of mycotoxin patulin was performed on 71 apple juices and concentrates and 21 infant fruit purees purchased from retail outlets or producers in Tunisia, by reversed-phase high-performance liquid chromatography using a C18 column with UV detection at 276 nm, keeping the recovery higher than 96% for spiking levels ranging between 30 and 100 ppb. The detection limit of the method was found to be 5 ppb. The findings showed that 12% of the samples locally produced in Tunisia were contaminated by patulin, with a maximum level of 6 ppb, and 5% of the samples imported and marketed in Tunisia were contaminated at a mean level less than 6 ppb. No detectable patulin contaminations for apple cider and infant fruit puree samples were found.