咖啡入面团能提升面包抗氧化能力吗？Can coffee in dough enhance the antioxidant capacity of bread?
（来源：中国食品报）
转自：中国食品报
“功能性面包”近年来成了烘焙圈的热词，往面粉里加点植物粉，既可补充膳食纤维、实现低GI特性，还能蹭点“抗氧化”的光环。咖啡粉因为自带“健康”人设，天然就被划进了这个名单。
咖啡面包早已不是新鲜事，从咖啡可颂到咖啡吐司，深色切面配上焦香风味，几乎成了“高级感”的标配。但本身具有抗氧化能力的咖啡加进面团，经过发酵、烘烤，这层“功力”到底还剩多少？是营销话术，还是真有科学依据？不妨从活性机理与烘焙实测两个维度寻找答案。
咖啡因何抗氧化？3类活性物质起作用
要判断咖啡粉能否提升面包的抗氧化能力，首先需要明确咖啡中的“抗氧化主力军”是谁，它们能否经受住面包制作的一整套工序考验。
咖啡的抗氧化能力并非单一成分的功劳，而是3类生物活性物质协同作用的结果。
第一类是酚酸类化合物，以绿原酸为首。它是咖啡中含量最高的酚类物质，生豆中占比可达4%—14.4%。绿原酸的优势在于“能打”——它能通过中和自由基、抑制炎症因子、调节抗氧化酶活性等多条通路发挥作用。虽然高温烘焙会让它部分降解，但即便是中深烘焙的咖啡豆，依然保留了可观的酚酸活性。当它被磨粉加入面团，这部分“残余”的绿原酸便有了迁入面包基质的机会。
第二类是生物碱——咖啡因与葫芦巴碱。咖啡因是人们最熟悉的咖啡成分，除了提神，它本身就具有一定的抗氧化和神经保护作用。葫芦巴碱则占咖啡豆干重的1%—3%，在烘焙过程中，虽然部分脱甲基会转化为烟酸，但其本身的抗炎、抗氧化活性依然存在。更重要的是，这类生物碱热稳定性较好，不会在后续的烘烤过程中轻易“全军覆没”。
第三类是烘焙产物——二萜类物质与类黑素。咖啡醇、咖啡豆醇等二萜类物质以及美拉德反应生成的类黑素，同样具备抗氧化、抗炎的生物学效应。尤其是类黑素，已被证实能通过抑制NF-κB等炎症通路，降低促炎因子水平。而这些物质本身就是咖啡粉的“出厂配置”。
从机理上看，咖啡粉里确实装着一整套“抗氧化工具箱”，但在面包的复杂体系里，这套工具箱还能不能打开？
面团里的两道关卡——发酵与烘烤
很多烘焙师担心，酵母发酵是否会把多酚“吃掉”？高温烘烤会不会将其毁掉？
根据目前有关的研究结果，答案或许比想象中乐观。
一方面，绿原酸在食品中表现出较好的热稳定性。研究人员曾用烘焙咖啡豆水提物替代面包配方中的水，对比面团与烤后面包的多酚组成，结果发现，烘烤并未显著降低面包的酚类含量与DPPH/ABTS清除率，抗氧化能力在焙烤前后基本一致。
另一方面，面团发酵时，酵母确实会消耗掉一部分小分子营养，但多酚类物质大多牢牢吸附、分布在面筋和淀粉交织的基质结构里，实际损耗非常有限。
一项以高筋小麦粉为基底、通过添加1%—4%梯度咖啡粉制作面包的对照实验结果显示，随着咖啡粉添加量的逐步提升，面包成品的总酚含量最高可提升29.6%，DPPH清除率提升133%，ABTS清除率提升60%。其中，咖啡粉添加量为2%时，成品面包的感官综合接受度达到峰值。
马来西亚大学开展的一项同类研究中，以3%、5%、7%梯度的绿咖啡粉（GCB）替代部分小麦粉制作面包，在220摄氏度条件下烘烤30分钟后，3%添加组的面包总酚含量有明显上升，DPPH自由基清除的IC50值从11.25毫克/毫升降至3.28毫克/毫升（该数值越低，代表自由基清除能力越强）。同时，样品中的铁离子螯合能力也显著上升。这一结果表明，即便经历完整的面包制作全流程，咖啡多酚的活性保留与组分协同效应，仍可大幅拉高面包的基础抗氧化水平。
添加咖啡粉一定要把握好“度”
抗氧化能力越强，不等于面包成品口感就越好。这就好比辣椒能提味，放多了反而会呛得让人难以下咽。
那么，添加多少咖啡粉，既能使抗氧化效果明显，同时又不影响风味？答案是2%。在此添加量下，面包表面呈浅黄褐色，光泽度最佳，风味评分最高。继续提升添加量，虽然抗氧化效果还能进一步提升，但会直接牺牲面包的蓬松度、质构表现与消费者接受度。绿原酸本身呈酸性，过量添加咖啡粉会破坏面筋网络的连续性，面包比容会有明显下降，芯部会出现发绿现象，苦涩味和类似“陈味”的异味也会凸显出来。
此外，用咖啡液代替配方水，操作虽然简便，但高温萃取本身已让部分多酚损失；用超细咖啡粉直接混入干料，热暴露时间更短，酚类保留通常优于液体法。
以下给烘焙师提出3点建议：
一是优先选用中浅烘咖啡豆研磨的超细粉，按面粉总重量的1.5%—2%加入面团，既能保证抗氧化活性的合理提升，又不会破坏面包的基础口感与质构。
二是采用常规200—220摄氏度完成熟化即可，无须刻意追求表皮深褐色。烘烤过度会导致咖啡中的多酚物质碳化，连原本能提升风味的类黑素也会发生劣变，反而破坏整体风味。
三是将咖啡粉与全麦粉、燕麦、核桃碎这类食材搭配使用，谷物自带的阿魏酸能和咖啡多酚形成活性叠加，让成品的抗氧化表现更加平稳持久。
（世烘）
(Source: China Food News)
Translated from: China Food News
Functional bread "has become a hot topic in the baking industry in recent years. Adding plant flour to flour can not only supplement dietary fiber and achieve low GI properties, but also add a touch of" antioxidant "aura. Coffee powder was naturally included in this list due to its inherent "healthy" persona.
Coffee bread is no longer a novelty, from coffee croissants to coffee toast, with dark cut surfaces and a smoky flavor, it has almost become a standard feature of "high-end". But when coffee, which has antioxidant properties, is added to the dough and fermented and baked, how much of this' power 'is left? Is it marketing rhetoric or does it really have scientific basis? You can look for answers from two dimensions: the mechanism of activity and baking tests.
How does caffeine resist oxidation? Three types of active substances work
To determine whether coffee powder can enhance the antioxidant capacity of bread, it is first necessary to clarify who the "main antioxidant force" in coffee is and whether they can withstand the entire process of bread making.
The antioxidant capacity of coffee is not solely attributed to a single component, but rather the result of the synergistic effect of three types of bioactive substances.
The first type is phenolic acid compounds, led by chlorogenic acid. It is the highest content of phenolic compounds in coffee, accounting for 4% to 14.4% in green beans. The advantage of chlorogenic acid lies in its ability to neutralize free radicals, inhibit inflammatory factors, and regulate antioxidant enzyme activity through multiple pathways. Although high-temperature roasting can partially degrade it, even coffee beans that are medium to deep roasted still retain considerable phenolic acid activity. When it is ground and added to the dough, this "residual" chlorogenic acid has a chance to migrate into the bread substrate.
The second type is alkaloids - caffeine and cucurbitacin. Caffeine is the most familiar coffee ingredient to people. In addition to refreshing, it itself has certain antioxidant and neuroprotective effects. Fenugreek accounts for 1% -3% of the weight of coffee dried tofu. During roasting, although part of demethylation will be converted to nicotinic acid, its anti-inflammatory and antioxidant activities still exist. More importantly, these alkaloids have good thermal stability and will not easily be completely destroyed during the subsequent baking process.
The third category is baked goods - terpenoids and melanoids. Diterpenoid substances such as caffeic acid and caffeic acid, as well as melanoids produced by the Maillard reaction, also have biological effects of antioxidant and anti-inflammatory. Especially melanin, it has been proven to reduce pro-inflammatory cytokine levels by inhibiting inflammatory pathways such as NF - κ B. And these substances themselves are the "factory configuration" of coffee powder.
From a mechanistic perspective, coffee powder does indeed contain a complete set of "antioxidant toolboxes", but in the complex system of bread, can this toolbox still be opened?
Two levels in dough - fermentation and baking
Many bakers are concerned whether yeast fermentation will "eat up" polyphenols? Will high-temperature baking destroy it?
According to current research findings, the answer may be more optimistic than imagined.
On the one hand, chlorogenic acid exhibits good thermal stability in food. Researchers have used roasted coffee bean water extract instead of water in bread formula to compare the polyphenol composition of dough and baked bread. The results showed that roasting did not significantly reduce the phenolic content and DPPH/ABTS clearance rate of bread, and the antioxidant capacity was basically the same before and after roasting.
On the other hand, during dough fermentation, yeast does consume some small molecule nutrients, but most polyphenolic substances are firmly adsorbed and distributed in the matrix structure interwoven with gluten and starch, and the actual loss is very limited.
A control experiment using high gluten wheat flour as the base and adding 1% -4% gradient coffee powder to make bread showed that as the amount of coffee powder gradually increased, the total phenolic content of the bread product could be increased by up to 29.6%, the DPPH clearance rate increased by 133%, and the ABTS clearance rate increased by 60%. When the amount of coffee powder added is 2%, the sensory acceptance of the finished bread reaches its peak.
In a similar study conducted by a Malaysian university, green coffee powder (GCB) with gradients of 3%, 5%, and 7% was used to replace some wheat flour to make bread. After baking at 220 degrees Celsius for 30 minutes, the total phenolic content of the bread in the 3% addition group increased significantly, and the IC50 value for DPPH radical scavenging increased from 11.25 mg/mL to 3.28 mg/mL (the lower the value, the stronger the free radical scavenging ability). At the same time, the chelating ability of iron ions in the sample also significantly increased. This result indicates that even after undergoing the entire bread making process, the activity retention and synergistic effect of coffee polyphenols can still significantly increase the basic antioxidant level of bread.
Adding coffee powder must be done in moderation
The stronger the antioxidant capacity, the better the taste of the finished bread. It's like chili peppers can enhance flavor, but adding too much can make it difficult to swallow.
So, how much coffee powder can be added to achieve significant antioxidant effects without affecting the flavor? The answer is 2%. At this addition level, the surface of the bread appears light yellow brown, with the best glossiness and the highest flavor rating. Continuing to increase the addition amount, although the antioxidant effect can be further improved, will directly sacrifice the fluffiness, texture performance, and consumer acceptance of the bread. Chlorogenic acid itself is acidic, and excessive addition of coffee powder can disrupt the continuity of the gluten network. The specific volume of bread will significantly decrease, and the core will appear green. Bitter and "aged" odors will also be highlighted.
In addition, using coffee liquid instead of formula water, although the operation is simple, the high-temperature extraction itself has already caused some polyphenol loss; Mixing ultrafine coffee powder directly into dry ingredients results in shorter heat exposure time and better retention of phenols compared to liquid methods.
Here are 3 suggestions for bakers:
Firstly, it is recommended to use ultra-fine powder ground from medium and light roasted coffee beans, and add it to the dough at a ratio of 1.5% to 2% of the total flour weight. This can ensure a reasonable increase in antioxidant activity without damaging the basic taste and texture of the bread.
The second option is to use a conventional temperature range of 200-220 degrees Celsius to complete the aging process, without the need to deliberately pursue a dark brown skin color. Overroasting can lead to carbonization of polyphenolic substances in coffee, and even melanoidins, which originally enhance flavor, can deteriorate, ultimately damaging the overall flavor.
Thirdly, coffee powder is used in combination with whole wheat flour, oats, and crushed walnuts. The inherent ferulic acid in grains can form an active superposition with coffee polyphenols, making the antioxidant performance of the finished product more stable and long-lasting.
(Shi Hong)