Effect of Traditional Processing on Beta-Carotene Content of Sweet Potato Products: A Systematic Review with Implications for Vitamin A Deficiency in Nigeria

Background Vitamin A deficiency (VAD) remains a severe public health problem in Nigeria, contributing to childhood blindness, compromised immunity, and maternal mortality. Orange-fleshed sweet potato (OFSP) is a rich source of β-carotene, the primary provitamin A carotenoid. However, traditional processing methods—boiling, roasting, frying, drying, and fermentation—may degrade β-carotene, potentially limiting the nutritional impact of OFSP products such as sweet potato garri. This systematic review synthesises available evidence on β-carotene retention in sweet potato subjected to traditional processing methods relevant to Nigeria. Methods A systematic search was conducted in PubMed, Google Scholar, and African Journals Online using keywords related to sweet potato, β-carotene, processing, and retention. Studies reporting quantitative β-carotene retention after boiling, roasting, frying, drying, or fermentation were included. Data were extracted on processing conditions, retention percentages, and factors affecting degradation. Results Fifteen studies met the inclusion criteria. Retention varied widely by method: boiling (65–85% retention), roasting (50–75%), frying (60–80%), sun drying (30–55%), oven drying (40–70%), and fermentation (50–70%). Key factors influencing retention included temperature, duration, exposure to light and oxygen, and matrix composition (e.g., fat content). No study directly examined β-carotene retention during traditional Garri processing (fermentation + dewatering + roasting) of sweet potato. Conclusion Traditional processing methods cause moderate to substantial losses of β-carotene in sweet potato, but significant provitamin A activity can still remain, especially with optimised conditions. For sweet potato Garri to serve as a meaningful VAD intervention, processing parameters (short fermentation, moderate roasting, addition of palm oil) should be standardised. Direct measurement of β-carotene retention in sweet potato Garri is an urgent research priority.