Browsing by Author "Stander, Marietjie"

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    Evaluating the influence of maceration practices on biogenic amine formation in wine
    (Elsevier, 2013) Smit, Anita Y.; Du Toit, Wessel J.; Stander, Marietjie; Du Toit, Maret
    Biogenic amines are formed during winemaking from precursor amino acids, mainly by lactic acid bacteria during malolactic fermentation (MLF). Various factors can influence the amino acid content of the grape must and wine; including contact with the grape skins before, during and after alcoholic fermentation. The quantity and composition of amino acids in the must can potentially dictate the subsequent formation of biogenic amines. In this study we investigate the influence of compounds extracted from the grape skins by different maceration practices applied during winemaking on the formation of biogenic amines. Wines were made on small scale with two red grape cultivars. Treatments consisted of free-run juice (no skin contact), skin contact during alcoholic fermentation, cold maceration and extended maceration; followed by MLF in all treatments. Our results show that higher levels of precursor amino acids and biogenic amines were detected in the absence of skin contact, extended maceration and to a lesser extent in conventional maceration. Cold maceration before fermentation initially increased the extraction of amino acids and formation of biogenic amines, but resulted in the lowest concentrations of these harmful compounds in the final wines. Cold maceration therefore appears to have a protective effect against biogenic amine accumulation during MLF.
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    Polyphenolic and physicochemical properties of simple-spined num-num (Carissa edulis) fruit harvested at ripe stage of maturation
    (MDPI, 2019-07-19) Makumbele, Fulufhelo P.; Taylor, Malcolm; Stander, Marietjie; Anyasi, Tonna A.; Jideani, Afam I. O.
    Wildly grown in most regions of the world, Carissa edulis is a highly underutilised fruit with significant antioxidant characteristics. The phyto and physicochemical properties of C. edulis berries at different stages of ripening are evaluated in this work. Total flavonoids (TF), total phenolic content (TPC) and antioxidant activity were determined spectrophotometrically, while concentration of polyphenols was determined using liquid chromatography coupled to diode array detection and electrospray ionization mass spectrometry. Results showed that antioxidant activity was lowest (18.36 ± 0.12 mmol TE/g) in RS3 and decreased with TPC upon increased ripening. Conversely, TF increased with ripening progression with TF found to be highest in RS3 (5.92 ± 0.03 mg CE/g). Identified phenolic acids in C. edulis were quinic acid, protocatechuoyl-hexose, neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid and dicaffeoylquinic acid. Identified flavonoids included rutin, catechin, procyanidin dimer, procyanidin trimer, quercetin-3-O-glucosyl-xyloside, quercetin-3-O-robinobioside, quercetin-3-O-glucoside and quercetin-3-OH-3-methylglutaryl-glucoside. Physicochemical properties of C. edulis varied among samples with sugar/acid ratio of C. edulis ranging from 25.70 for RS1 to 50.36 for RS3. Ripening stage of C. edulis undoubtedly affects the phyto and physicochemical properties of C. edulis.