Spoilage-yeast metabolism, reduced-sugar formulations and implications for food preservation

腐败酵母代谢、减糖配方以及对食品保存的影响

• 批准号: BB/T014784/1
• 负责人: Simon Avery
• 金额: $ 55.9万
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FT014784%2F1
• 关键词: Spoilage; yeast; metabolism; reduced; sugar

Fungi (yeasts and moulds) spoil 5-10% of all food and drinks produced globally, costing many billions of pounds each year. This contributes significantly to food insecurity. A variety of strategies is used to preserve foods but these are not always effective. In the soft drinks industry, formulations have been developed over a number of years that help to limit the spoilage problem to current levels. The drinks are usually acidic and usually inhibit bacteria. However, yeasts can grow in these conditions and they commonly dominate in soft drinks spoilage. A principal preservative used in soft drinks is the weak acid sorbic acid. This inhibits most yeasts, but a number can still grow at the permitted levels and some can degrade the sorbic acid to products that alter flavour. The resultant chronic level of yeast spoilage in soft drinks manufacture could be set to worsen, as recent market pressures have been prompting major re-formulation of soft drinks products. The 'Soft Drinks Industry Levy' implemented by the UK government in 2018 aligned with similar moves made by certain other governments. As a result, many manufacturers have decreased the sugar content of drinks formulations from more than 10% to less than 5%. However, there is little understanding of how these re-formulations may impact preservative efficacy and spoilage. Reports from the industry indicate a rise in incidence of certain spoilage yeasts since introduction of the reduced-sugar products. Our preliminary studies have illustrated how metabolism of spoilage yeasts is markedly altered by changes in sugar content below 5%. The yeasts shift from a type of metabolism termed fermentation to another, respiration, as sugar level is decreased. Importantly, this shift coincides with marked changes in the yeasts' abilities to resist preservative. Furthermore, these effects are not the same for all individual yeast cells in a population, a phenomenon known as 'heteroresistance', which can be a particular problem for spoilage control. Besides reduced sugar, there is also growing market pressure to use natural products in place of chemical preservatives, for cleaner label drinks products. This project focuses on understanding the impacts of these changes in drinks formulations for yeast metabolism and preservative resistance, and for spoilage control. We will investigate this by testing yeasts in low sugar conditions, which can be precisely controlled using a technology known as microfluidics. This technology also allows us to examine single yeast cells, as some individual cells can be highly resistant to preservative. We will apply the latest genetic technology to single cells to find out what makes them resistant and we will then exploit that information to find alternative agents that could give better inhibition at different sugar levels. Importantly, this will encompass tests of candidate natural-product activities, including some promising candidates from our industry partner supporting this project. The proposed project could offer solutions to give more-complete inhibition of spoilage yeasts in new formulations, an area of particular interest to the industry partner. While soft drinks and resistance to preservatives (including natural products) at different sugar levels provide the exemplar for this work, the knowledge generated will help develop strategies for preventing yeast food spoilage more broadly.

真菌（酵母和霉菌）破坏了全球生产的所有食品和饮料的5-10%，每年造成数十亿英镑的损失。这在很大程度上加剧了粮食不安全。人们使用各种策略来保存食物，但这些策略并不总是有效的。在软饮料行业，多年来已经开发出有助于将腐败问题限制在当前水平的配方。这些饮料通常是酸性的，通常能抑制细菌。然而，酵母菌可以在这些条件下生长，它们通常在软饮料腐败中占主导地位。软饮料中使用的主要防腐剂是弱酸性山梨酸。这抑制了大多数酵母菌，但仍有一些可以在允许的水平上生长，有些可以将山梨酸降解为改变风味的产品。软饮料生产中酵母腐败的慢性水平可能会恶化，因为最近的市场压力促使软饮料产品的重大重新配方。英国政府于2018年实施的“软饮料行业税”与其他一些政府的类似举措保持一致。因此，许多制造商已将饮料配方的糖含量从超过10%降至低于5%。然而，很少有人了解这些重新配方可能会影响防腐剂的功效和腐败。来自该行业的报告表明，自引入低糖产品以来，某些腐败酵母的发生率有所上升。我们的初步研究已经说明了如何腐败酵母代谢显着改变糖含量低于5%的变化。随着糖水平的降低，酵母从一种称为发酵的代谢转变为另一种称为呼吸的代谢。重要的是，这种转变与酵母抵抗防腐剂能力的显著变化相吻合。此外，这些影响对于群体中的所有单个酵母细胞是不相同的，这种现象称为“异源抗性”，这可能是腐败控制的一个特殊问题。除了还原糖，使用天然产品代替化学防腐剂的市场压力也越来越大，用于更清洁的标签饮料产品。该项目的重点是了解这些变化对饮料配方酵母代谢和防腐剂抗性以及腐败控制的影响。我们将通过在低糖条件下测试酵母来研究这一点，这可以使用一种称为微流体的技术来精确控制。这项技术还允许我们检查单个酵母细胞，因为一些单个细胞对防腐剂具有高度抗性。我们将把最新的遗传技术应用于单细胞，以找出是什么使它们具有抗性，然后我们将利用这些信息来寻找替代药物，这些药物可以在不同的糖水平下提供更好的抑制作用。重要的是，这将包括对候选天然产物活性的测试，包括我们支持该项目的行业合作伙伴的一些有前途的候选物。拟议的项目可以提供解决方案，在新配方中更全面地抑制腐败酵母，这是行业合作伙伴特别感兴趣的领域。虽然软饮料和对不同糖水平的防腐剂（包括天然产品）的抗性为这项工作提供了范例，但所产生的知识将有助于更广泛地制定预防酵母食品腐败的策略。