The effect of heating at different temperatures (60, 80, 90, 110, and 130 °C) on the total phenolic content, antioxidant activity, and phenolic compounds present in plum and mahaleb fruits was investigated. The antioxidant activity values and total phenolic contents of fresh plum (93.82% measured by DPPH method, 787.79 mg gallic acid equivalent (GAE)/100 g dry weight determined by Folin method) and mahaleb fruits (81.80%, 634.47 mg GAE/100 g dry weight) were higher than plum and mahaleb fruits dried at different temperatures ( p < 0.05). Generally, the heating process caused a reduction in both total phenolic content and antioxidant activity for plum and mahaleb. While (+)-catechin (92.62 mg/kg), 1,2-dihydroxybenzene (132.15 mg/kg), gallic acid (107.01 mg/kg), and 3,4-dihydroxybenzoic acid (74.59 mg/kg) are the key phenolic compounds in fresh plum, (+)-catechin, 3,4-dihydroxybenzoic acid, 1,2-dihydroxybenzene, and syringic and caffeic acids were the major phenolic compounds of mahaleb fruits. The polyphenol content of fruits and the class of phenolics present are significantly affected by heating temperature.

In the current study, we examined the effects of boiling cauliflower in a pressure cooker, conventional boiling, conventional heating, and microwave heating on the chemical components, total phenol, flavonoids, antioxidant capacity (DPPH test), phenolic compounds, and mineral contents of cauliflower florets to reveal the differences between these cooking methods. Cauliflower is generally consumed either boiled or cooked in dry heat. In this study, different boiling and dry heat cooking methods were tried to reveal the changes in phytochemical composition and protein and mineral contents of cauliflower florets. Depending on the cooking methods of the cauliflower florets, the total phenolic and flavonoid contents of the cauliflower florets were determined to be between 273.72 (conventional heating) and 731.01 mg GAE/100 g (microwave heating) and 142.02 (conventional heating) and 797.10 mg/100 g (conventional boiling), respectively. The antioxidant capacity results of cauliflowers were found to be between 8.30 (conventional heating) and 33.69 mmol/kg (fresh). Statistically significant differences were detected in the moisture, total phenol, total flavonoid, and antioxidant activity values of cauliflower depending on the cooking techniques applied (p < 0.05). The gallic acid and 3,4-dihydroxybenzoic acid values of fresh and cooked cauliflowers were identified to be between 10.93 (microwave heating) and 194.79 mg/100 g (boiling in pressure cooker) and 17.58 (conventional heating) and 145.80 mg/100 g (boiling in pressure cooker), respectively. In general, the lowest amounts of phenolic compounds were defined in cauliflower samples boiled with a conventional heating system, followed by cauliflower samples cooked with the microwave heating method. Considering the component amounts as a result of cooking, the highest phenolic component amounts were specified in the cauliflower sample cooked by boiling in a pressure cooker. The protein quantities of fresh and cooked cauliflowers were determined to be between 16.11 (fresh) and 19.79% (microwave heating). The K and S contents of fresh cauliflowers and cauliflowers cooked with different blanching methods were specified to be between 19,647.62 (conventional boiling) and 35,130.01 mg/kg (conventional heating) and 3196.54 (boiling in pressure cooker) and 5105.65 mg/kg (microwave heating), respectively. The K, Mg, S, Fe, Cu, Mn, and Zn results of cauliflowers cooked in an oven and microwave were higher than those cooked using the control and boiling methods.

In this study, the effect of oven and microwave roasting at different times on oil content, total phenol, flavonoid, fatty acids, phenolic components and mineral contents of purslane seeds was investigated. The total phenolic quantities of the purslane seeds roasted in the oven and microwave were characterized to be between 252.0 ± 1.80 (180 °C/5 min in the oven) and 256.6 ± 3.51 (10 min in the oven), and between 216.3 ± 0.28 (720 W/15 min in the microwave) and 203.7 ± 1.93 GAE/100 g (30 min in the microwave), respectively. The highest total flavonoid (613.8 ± 4.36 mg QE/100 g) was detected in the application of roasting in the oven for 10 min. Roasting in the oven for 5 min caused a decrease in the total flavonoid content (584.3 ± 4.95 mg QE/100 g), while roasting for 10 min caused an increase in the flavonoid content (613.8 ± 4.36 mg QE/100 g). The oil yields of purslane seed samples roasted in the oven for 5 min and 10 min were defined as 40.40 ± 0.99% and 45.00 ± 0.71%, respectively. Statistical differences were observed between the oil, total phenol and flavonoid contents of the samples depending on the roasting times in the oven and microwave (p ≤ 0.01). The protein contents of the purslane seeds were established to be between 27.89 ± 0.279% (control) and 37.24 ± 0.407% (10 min in the oven). The calcium (Ca) contents of the purslane seeds changed between 8314.99 ± 327.53 ppm (5 min in the oven) and 4340.62 ± 498.45 ppm (15 min in the microwave), while the phosphorus contents varied between 4905.13 ± 43.02 ppm (15 min in the microwave) and 4051.23 ± 6.39 ppm (unroasted). In addition, the potassium content was found to be between 4565.89 ± 153.47 (5 min in the oven) and 3904.02 ± 7.17 ppm (unroasted). It was also observed that the purslane seeds roasted in the oven for 10 min maintained a linolenic fatty acid content of up to 65.57%. Considering the bioactive properties and phytochemical components of purslane seeds roasted in both roasting systems, they are important in terms of the nutritional enrichment of foods as a food supplement.

In this study, the effects of oven dehydration on chemical and bioactive properties, fatty acids, polyphenolic compounds and minerals of sandal strawberry tree fruit were investigated. While total carotenoid contents of the sandal strawberry tree fruit are determined between 4.20 (120 °C) and 5.43 µg/g (70 °C), tannin amounts of the sandal strawberry tree fruit were recorded between 5.13 (control) and 6.37% (70 and 120 °C). While total phenolic contents of dehydrated sandal strawberry tree fruit were found between 444.16 (120 °C) and 665.13 mgGAE/100 g (control), total flavonoid amounts of dehydrated sandal strawberry tree fruit were recorded between 592.91 (control) and 788.71 mg/100 g (120 °C). Antioxidant activity values of fruit ranged from 4.10 (120 °C) to 7.30 mmol TE/kg (control). Both total phenolic amounts and antioxidant activity values of untreated (control) sandal strawberry tree fruit were found to be higher than dehydrated ones, and a linear relationship was determined between the total phenolic amounts of the samples and their antioxidant activities. The highest amounts of phenolic compounds (ferulic acid, resveratrol and kaempferol) were detected in strawberry tree fruit dehydrated at 70 °C, followed by the control group and fruit dehydrated at 120 °C in decreasing order. Gallic acid, 3,4-dihydroxybenzoic acid, catechin, caffeic acid and rutin were the main constituents of the strawberry tree fruit, followed by syringic acid, p-coumaric acid and ferulic acid in descending order. Palmitic, stearic and oleic acid amounts of dehydrated strawberry tree fruit oils compared to the control were observed to increase with the applied temperature, while the contents of polyunsaturated fatty acids (linoleic and linolenic) decreased. In general, the mineral content of dehydrated strawberry tree fruit increased compared to the control. Since the oil, carotenoid, total phenol and phenolic component contents of sandalwood tree fruit are higher in the sample subjected to dehydration at 70 °C, this temperature can be considered as the ideal one for drying. In addition, considering the fatty acids, heat treatment at 120 °C can be preferred.

In this study, the role of different roasting temperatures on oil amount, total phenolic contents, total flavonoid quantities, antioxidant capacity, polyphenol, fatty acid and mineral profiles of roasted-carob fruit powders was revealed. The oil and protein amounts of the carob powders were specified to be between 0.40 (90 °C) and 0.85% (control) to 8.40 (120 °C) and 10.27% (control), respectively. Total phenolic and flavonoid quantities of the raw (control—unroasted) and roasted carob powders were defined to be between 781.16 (control) and 903.07 mg GAE/100 g (150 °C) to 663.81 (control) and 1141.90 mg/100 g (150 °C), respectively. In addition, antioxidant activities of the carob powders were measured to be between 9.27 (150 °C) and 10.30 mmoL/kg (control). Gallic acid and 3,4-dihydroxybenzoic acid amounts of the carob powders were specified to be between 45.16 (control) and 120.66 (150 °C) to 7.06 (control) and 20.46 mg/100 g (150 °C), respectively. Palmitic, oleic and linoleic acids were the key fatty acids of carob oils. It is thought that the fatty acid compositions of carob powder oil, which is generally subjected to heat treatment, are negatively affected by high temperatures. Especially, the linoleic and linolenic acid amounts of the oil samples decreased significantly after 90 °C. The highest element was potassium, followed by Ca, P, Mg, S, Fe, Na, Pb, Cu, Zn B and Mn, in descending order.

In this study, the effect of different cooking techniques on broccoli moisture, total phenolic, total flavonoid, and radical scavenging capacity results, polyphenol contents, and their quantitative values was investigated. The total phenolic quantities of fresh and cooked broccoli samples were assessed to be between 36.32 (conventional boiling) and 423.39 mg GAE/100 g (microwave heating). The radical scavenging activities of the broccoli samples were reported between 2.55 (conventional boiling) and 4.99 mmol/kg (microwave heating). In addition, catechin and rutin quantities of the fresh and cooked broccoli samples were measured to be between 2.24 (conventional boiling) and 54.48 mg/100 g (microwave heating), and between 0.55 (conventional boiling) and 16.33 mg/100 g (microwave heating), respectively. The most abundant elements in fresh and cooked broccoli samples were K, Ca, P, S, and Mg. The results showed some changes depending on cooking techniques compared to the control. The bioactive properties of broccoli samples cooked by means of conventional boiling, boiling in vacuum bag, and high-pressure boiling were established to be lower compared to the fresh sample. Catechin, 3,4-dihydroxybenzoic acid, rutin, and gallic acid were the key phenolic compounds of fresh and cooked broccoli samples. The phenolic components of broccoli were significantly affected by the applied cooking techniques. The highest protein in broccoli samples was determined in the broccoli sample cooked by boiling in a vacuum bag. There were statistically significant changes among the mineral results of broccoli cooked with different cooking methods.