Laboratory of Valorization and Quality Management of Food Bio-Ingredients (LaBio), DNSA/FSA, Université d'Abomey-Calavi, Cotonou, Benin.
Food Quality and Design, Wageningen University, Wageningen, The Netherlands.
PLoS One. 2018 Mar 21;13(3):e0194657. doi: 10.1371/journal.pone.0194657. eCollection 2018.
Sorghum (Sorghum bicolor) extract is traditionally used as red biocolorant in West Africa to colour foods, among which wagashi, a soft cheese. This biocolorant is a source of the phytoalexin apigeninidin and phenolic acids, and users claim that it has preservative effects next to its colouring properties. If such a claim can be scientifically substantiated, it adds a valuable functional property to this natural red colorant, thereby increasing its potential applications in the food industry. Hence, the present study evaluated the antimicrobial properties of dye sorghum extracts using challenge tests in broth and wagashi as a model of a popular food application. The alkaline extract and hot aqueous extract were used for dyeing wagashi by 87.7% and 12.3% of the traders, respectively. The dyeing procedure is perceived as a preservation strategy, and is also a means to maximise the revenues. However, results demonstrated that the application of sorghum biocolorant on wagashi had no inhibitory effect on the growth of fungi (Penicillium chrysogenum, Cladosporium macrocarpum) and Escherichia coli O157:H7. Furthermore, sorghum biocolorant in broth had no effect on growth of Listeria monocytogenes and Escherichia coli O157:H7. Consequently, the commonly used extracts for colouring soft West-African cheese did not show a preservative effect. In addition, dyeing did not affect the physico-chemical properties of wagashi. Still, the red colour hampered visual detection of microbial growth, thus clarifying the preservative effect reported by users.
高粱（高粱）提取物在传统上被用作西非的红色生物着色剂来给食物上色，其中包括奶酪 wagashi。这种生物着色剂是植物抗毒素芹菜素苷元和酚酸的来源，使用者声称它除了具有着色特性外，还有防腐作用。如果这样的说法可以在科学上得到证实，那么它将为这种天然红色着色剂增加有价值的功能性属性，从而增加其在食品工业中的潜在应用。因此，本研究使用挑战试验在肉汤和 wagashi 中评估了高粱提取物的抗菌性能， Wagashi 是一种受欢迎的食品应用模型。碱性提取物和热水提取物分别用于对 wagashi 进行染色，分别占贸易商的 87.7%和 12.3%。染色过程被视为一种保存策略，也是最大限度提高收入的手段。然而，结果表明，高粱生物着色剂在 wagashi 上的应用对真菌（青霉素、大孢枝孢菌）和大肠杆菌 O157:H7 的生长没有抑制作用。此外，肉汤中的高粱生物着色剂对李斯特菌和大肠杆菌 O157:H7 的生长没有影响。因此，用于给西非软奶酪上色的常用提取物没有显示出防腐作用。此外，染色不会影响 wagashi 的物理化学性质。尽管如此，红色还是阻碍了微生物生长的视觉检测，从而澄清了使用者报告的防腐效果。
