Black garlic (BG) is a product originating from fresh garlic (FG) and substantially differs in many aspects from FG due to the process called ageing. During this thermal process, the health-promoting properties of FG are enhanced, and the sensory traits are altered. However, very little is known about how the physicochemical properties of different FG varieties affect these properties of BG. Thus, the aim of this study was to investigate the influence of seven FG varieties subjected to the thermal process on the physicochemical parameters of BG. To prepare the BG samples, a fifteen-day ageing process involving a temperature gradient ranging from 30 to 82 °C was used. It was found that the antioxidant activity, the total polyphenol content, and the total soluble solids increased during ageing, while the pH level, moisture content, and lightness decreased in all the garlic varieties. The varieties of garlic differed in the studied traits significantly, both before (FG) and after ageing (BG). In the sensory analysis, significant differences between the BG varieties were observed only in the pleasantness of texture, while the remaining sensory descriptors (pleasantness of color, odor, taste and intensity of the garlic aroma, and overall acceptability) were not affected by variety. The correlations suggest that most of the FG’s studied parameters in this study do not correlate with the properties of BG and cannot be used for the prediction of the quality of BG. Additionally, HPLC-MS/MS analysis revealed substantial changes in the composition of low molecular compounds.

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Mechanically separated fish meat (MSFM) can be used for the manufacturing of ready-to-eat products, such as sausages; however, it is highly perishable. Several plant by-products, including onion peel, which is rich in polyphenol antioxidants, can be added to food to extend shelf life. This study investigated the effects of the addition of onion peel powder (OPP) to sausage made from MSFM. Sausages were divided into four groups with different amounts of added OPP: 0% (control), 1%, 2%, and 3%. Cooked sausages were stored for 28 days at 5 °C. Samples were analyzed for thiobarbituric acid reactive substances, antioxidant activity, total polyphenol content, pH, and organoleptic properties. The addition of OPP significantly increased antioxidant activity and total polyphenol content and decreased pH, indicating acidic nature of OPP. Polyphenols from OPP effectively suppressed lipid oxidation. A 1–2% addition of OPP enhanced sensory properties. After the 28-day storage, the control samples received the lowest sensory score, due to the presence of a strong fishy odor, which was not present in samples with OPP. HPLC–MS/MS analysis revealed that quercetin is the most dominant compound in OPP. Overall, the results indicate that the addition of OPP in amounts of 1–2% can extend shelf life, without the deterioration of sensory properties.

Onion skin is a waste produced in thousands of tons annually in the European Union. It is a rich natural source of flavonoids and its water extracts (as an environmentally friendly solvent) could be used as an antioxidant material for meat products. Therefore, antioxidant properties of onion skin water extracts (OSWEs) were tested on cooked pork patties. Pork patties were divided into five treatments: control (no antioxidant), 10 and 20% (w/w) of yellow OSWE, and 10 and 20% (w/w) of red OSWE. Antioxidant activity, total polyphenols, thiobarbituric acid reactive substances (TBARS), and sensory analysis were assessed. Patties with added antioxidants showed significantly (P < 0.05) higher antioxidant activity and total polyphenol content. Samples with OSWEs, after 5-day storage (5°C), had significantly (P < 0.05) lower TBARS values compared to control. Two main phenolic compounds were identified in OSWEs by liquid chromatography – mass spectrometry using electrospray ionisation in negative mode: quercetin (m/z 301) and quercetin monoglucoside (m/z 463). OSWEs demonstrated the potential to be used as a source of natural antioxidants with strong antioxidant activity in meat products.

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