The Potential of Exploiting Economical Solar Dryer in Food Preservation: Storability, Physicochemical Properties, and Antioxidant Capacity of Solar-Dried Tomato (Solanum lycopersicum) Fruits.

This study investigated the effect of solar drying on storability and physiochemical and antioxidant capacities of dried tomatoes. Sliced fruit was dried at 45 ± 2 °C for 24 h under a solar tunnel dryer and stored at ambient temperature for 90 and 180 days. Solar drying treatments significantly (p < 0.05) reduced the bacterial and mold load, and eliminated Staphylococcus aureus, S. saprophyticus, and Escherichia coli in all samples. Solar drying treatment reduced the water activity of the dried tomato's to 0.31 that remained at the same level during storage period 180 days. Storage of dried tomato slices resulted in the decrease of both color and vitamin C content while it increased the total carotenoid, lycopene, phenolic compound content, and antioxidant activity. Furthermore, the principle component analysis (PCA) revealed that solar drying of tomato slices enhanced its physicochemical properties, antioxidant capacity particularly after storage for 90 and 180 days. Interestingly, the solar drying process enhanced tomato slices storage and physicochemical characteristics, that resulted in extending the shelf life by up to 6 months, indicating the great potential application of low-tech solar in food industry and could become an emerging effective post-harvest preservative method for seasonal perishable vegetable and fruit, particularly in developing countries.

Influence of Drying Methods on Bioactive Properties,Fatty Acids and Phenolic Compounds of Different Parts of Ripe and Unripe Avocado Fruits.

All drying processes increased oil content, antioxidant activity, total phenolic contents, and most of the phenolic compounds in the pulp, peel and seeds of both ripe fruits with varied degrees (p < 0.05). In addition, the processes reduced the oil contents, linoleic acids, 3,4-dihydroxybenzoic acid, (+)-catechin, and naringenin of the pulp, antioxidant activity of the peels and seeds, and 3,4-dihydroxybenzoic acid, (+)-catechin of the seeds and it enhanced all other parameters in the pulp, peel, and seeds of unripe fruits (p < 0.05). Comparing the phenolic profiles of avocado pulp, peels, and seeds of ripe and unripe fruits indicated that the peel and seeds are richer than the pulp and that is superior in unripe fruits than ripe ones. In addition, drying processes particularly microwave and air drying greatly enhanced the bioactive properties of ripe and unripe avocado fruits and could thus be used to elongate the shelf-life of avocado fruit products without major impact on the overall quality.

Bioactive compounds, nutritional and sensory properties of cookies prepared with wheat and tigernut flour.

This study aimed to evaluate cookies made with wheat (0%, 80%, 60%, and 50%) and tigernut flour (0%, 20%, 40%, and 50%) from two different sources. Standard methods were applied to determine the chemical properties, phenolic component, fatty acid composition, mineral content, and sensory properties of cookies. Tigernut flour from both sources was rich in oil, and total and individual phenolics, but with low antioxidant activity compared to wheat flour. The addition of tigernut flour to wheat resulted in increase of the content of bioactive compounds, minerals, and fatty acid contents of cookies. The cookies produced by formulating wheat with tigernut had a comparable organoleptic quality scores to wheat flour cookies. The production of cookies with both wheat and tigernut flour showed that this mixture is an interesting opportunity to have a functional product rich in bioactive compounds and considered satisfactory by consumers.

Influence of drying techniques on bioactive properties, phenolic compounds and fatty acid compositions of dried lemon and orange peel powders.

Lemon peel powder (LPP) obtained after drying (microwave, infrared, and oven) showed the lowest (58.72%) DPPH-radical scavenging activity in oven-dried and the highest (67.84%) in infrared-dried LPP while that of fresh lemon peel remained 63.22%. Orange peel powder (OPP) showed the lowest DSA (61.65) after microwave and the lowest (63.54%) after infrared-drying while that of fresh orange peel was 63.48%. Total phenolics were between 114.58 (fresh) and 179.69 mgGAE/100 g (oven) in LPP and between 158.54 (fresh) and 177.92 mgGAE/100 g (infrared) in OPP. The total flavonoid contents were 380.44 (fresh)-1043.04 mg/100 g (oven) in case of LPP and 296.38 (fresh)-850.54 mg/100 g (oven) in case of OPP. The gallic acid contents were 2.39 (fresh)-14.02 mg/100 g (oven) in LPP. The (+)-catechin contents were 1.10 (fresh)-49.57 mg/100 g (oven) for LPP and 0.82 (fresh)-7.63 mg/100 g (infrared) in case of OPP. The oleic acid content was 22.99 (infrared)-58.85% (fresh) in LPP-oil and 28.59 (microwave)-61.65% (fresh) in OPP-oil. The linoleic acid contents were 13.76 (fresh)-36.90% (oven) in LPP-oil and 14.14 (fresh)-37.08% (infrared) in case of OPP-oil. The drying techniques showed profound but variable effects on radical scavenging activity, total phenolics, flavonoid, carotenoids, phenolic compounds and fatty acid composition of both LPP and OPP and oven-drying (60 °C) was the most effective in improving these bioactive constituents.

Effect of Microwave Treatment on Oil Contents, Fatty Acid Compositions and Mineral Contents of Hazelnut Varieties.

The oil content of both 'raw' and hazelnut kernels was significantly (p < 0.05) reduced as the microwave power increased from 180 W to 360 W. The contents of fatty acids flucuated for all varieties with microwave power, with a significant (p < 0.05) increment observed for 'Sivri' hazelnut at 180 and 720 W. The maximum linoleic acid contents for 'Raw', 'Sivri' and 'Tombul' hazelnuts were found as 11.87%, 12.61% and 17.68% for nuts roasted at 540 W, unroasted and those roasted at 720 W, respectively. It was observed that K (9735.1 mg/kg) and Mg (2343.7 mg/kg) contents of the investigated samples were found at the maximum levels in unroasted 'Tombul' hazelnut, while the highest P (2845.0 mg/kg) and S (1795.3 mg/kg) contents are determined for hazelnut roasted at 720 W (p < 0.05). The highest Ca content in hazelnut kernel was also observed at 360 W with 2400.9 mg/kg. However, roasting process did not dramatically affect the mineral contents of samples.

Effect of Rosemary Extracts on Stabilitiy of Sunflower Oil Used in Frying.

The oxidative stability of sunflower oil containing rosemary essential oil and extracts in the oil during frying were followed by measuring peroxide value. Variation in the values of L* of the frying oil containing extract was less than that of frying oil containing essential oil. a*-Value of the fried oil containing extract highly significant decreased. Increase in the value of b* of 1. and 2. frying oil with 0.5 % rosemary essential oil was less. b* Value of the frying oils containing rosemary extract increased compared to b* values of frying oils containing essential oil. b* Value of the frying oil that the essential oil of rosemary added showed less increase than b* value of the frying oil that extract of rosemary. The viscosity values of frying oils containing rosemary extract changed between 30.3 mPas (1. frying oil containing 0.5% extract) and 35.5 mPas (2. frying oil containing 0.5% extract). In addition, free fatty acidity values of frying oils containing essential oil at 0.1, 0.3 and 0.5% levels ranged from 0.160% (1. frying oil containing 0.5% essential oil) to 0.320% (1. frying oil containing 0.3% essential oil). Peroxide values of frying oils containing rosemary extracts were determined between 12.84 meq O2/kg (1. frying oil containing 0.1% extract) and 28.98 meq O2/kg (2. frying oil containing 0.1% extract). Peroxide value of frying made with 0.3 % the rosemary essential oil increased less than that of made with the raw sunflower oil (control) (p < 0.05). Whenever rosemary essential oil and rosemary extract compare, the essential oil seems to be more effective on the peroxide value of the frying oil. The essential oil of rosemary have been effected more from the extracts of rosemary on the oxidative stability of sunflower oil.