Articles
Effects of moderate pretreatments and fermentation on the chemical composition and bioactive properties of marula fruit juice and wine
Article number
1466_3
Pages
19 – 26
Language
English
Abstract
Marula fruit juice is highly valued for its richness in nutrients and bioactive compounds, which promote good health.
Extreme pretreatment conditions of the fruits have shown to significantly deplete total phenolic content (TPC) and antioxidant capacity of the juice.
To mitigate these losses, this study investigated the impacts of moderate temperature pretreatments (ice-cold and heat) applied to the whole marula fruits prior to juice extraction and subsequent fermentation.
Untreated whole fruits served as the control.
Following juice extraction, all samples were pasteurised at 80°C for 5 min and subsequently fermented under static conditions using Saccharomyces cerevisiae at 30°C. Physicochemical and chemical analyses were conducted pre- and post-fermentation, evaluating pH, total titratable acidity (TTA), ash content, individual sugars and ethanol yields.
Bioactive evaluations were quantified using the Folin-Ciocalteu method for TPC and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay for antioxidant activity.
Prior to fermentation, the initial pH across all the groups remained similar, though the juice derived from the ice-cold pretreated fruits exhibited slightly lower pH 3.4. The untreated control juice demonstrated the lowest TTA (0.83%, p<0.05) but retained the highest ash content at 7.6% (p<0.05). The carbohydrate of the untreated control juice was characterised by 38.37 mg mL‑1 sucrose, 39.23 mg mL‑1 glucose, and 27.16 mg mL‑1 fructose.
Regarding bioactive preservation, the juice extracted from ice-cold pretreated fruits yielded DPPH antioxidant scavenging activity of 55% and TPC of 63 mg GAE mL‑1. Following alcoholic fermentation, both metrics increased significantly (p<0.05), to 60.5% antioxidant activity and a TPC of 82 mg GAE mL‑1. The vitamin C content remained stable above 138 mg 100 g‑1 in all the juices extracted from pretreated fruits and post fermentation.
Ultimately, final ethanol yield remained slightly above 7% alcohol by volume (v/v), showing no significant differences between the fermented pretreated and control juices.
Extreme pretreatment conditions of the fruits have shown to significantly deplete total phenolic content (TPC) and antioxidant capacity of the juice.
To mitigate these losses, this study investigated the impacts of moderate temperature pretreatments (ice-cold and heat) applied to the whole marula fruits prior to juice extraction and subsequent fermentation.
Untreated whole fruits served as the control.
Following juice extraction, all samples were pasteurised at 80°C for 5 min and subsequently fermented under static conditions using Saccharomyces cerevisiae at 30°C. Physicochemical and chemical analyses were conducted pre- and post-fermentation, evaluating pH, total titratable acidity (TTA), ash content, individual sugars and ethanol yields.
Bioactive evaluations were quantified using the Folin-Ciocalteu method for TPC and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay for antioxidant activity.
Prior to fermentation, the initial pH across all the groups remained similar, though the juice derived from the ice-cold pretreated fruits exhibited slightly lower pH 3.4. The untreated control juice demonstrated the lowest TTA (0.83%, p<0.05) but retained the highest ash content at 7.6% (p<0.05). The carbohydrate of the untreated control juice was characterised by 38.37 mg mL‑1 sucrose, 39.23 mg mL‑1 glucose, and 27.16 mg mL‑1 fructose.
Regarding bioactive preservation, the juice extracted from ice-cold pretreated fruits yielded DPPH antioxidant scavenging activity of 55% and TPC of 63 mg GAE mL‑1. Following alcoholic fermentation, both metrics increased significantly (p<0.05), to 60.5% antioxidant activity and a TPC of 82 mg GAE mL‑1. The vitamin C content remained stable above 138 mg 100 g‑1 in all the juices extracted from pretreated fruits and post fermentation.
Ultimately, final ethanol yield remained slightly above 7% alcohol by volume (v/v), showing no significant differences between the fermented pretreated and control juices.
Publication
Authors
L.M. Legodi, M.L. Mamabolo, M.J. Mothapo, K.L.M. Moganedi
Keywords
marula fruits, Sclerocarya birrea, fruit pretreatment, bioactive compounds, marula fruit wine
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