In November 2015 the US FDA sought public comments on the use of the term “natural” in food labeling. Over 7,000 comments were submitted to the FDA illustrating wide and varied opinions on the term natural. Some found it surprising the FDA does not have an existing definition of “natural” food, but this is not a unique issue in the United States. No major regulatory agency in the world that oversees food labeling defines natural ingredients in food, with the exception of natural flavors. The US FDA, European Food Safety Authority (EFSA), Japanese Ministry of Health, and other regions have clear requirements for labeling flavors as “natural.” The different global definitions of natural flavors can vary significantly and methods for analyzing and confirming natural status are likewise diverse. A brief description of the some key regional natural flavor definitions follows as well as information on analytical verification methods.
2015年11月，美国FDA就食品标签中“天然”一词的使用征求公众意见。超过7000条评论被提交给FDA，说明了对“天然”一词广泛而不同的看法。有些人对FDA没有“天然”食品的现有定义感到惊讶，但这并不是美国独有的问题。除了天然香料外，世界上没有监管食品标签的主要监管机构对食品中的天然成分进行定义。
美国食品药品监督管理局(FDA)、欧洲食品安全局(EFSA)、日本厚生劳动省等地区对标注“天然”香料有明确要求
。
全球对天然香料的定义各不相同，分析和确认天然状态的方法也各不相同
。本文简要介绍了一些关键的区域对天然香料定义，以及分析验证方法的信息。
US Natural Flavors 美国天然
Natural flavors are defined in the United States under regulation 21 CFR 101.22. The key definitions in this regulation are “The term natural flavor or natural flavoring means … any product of … plant material, meat, …, eggs, dairy products, or fermentation products thereof, whose significant function in food is flavoring….” This definition identifies many types of natural raw materials and some methods for producing raw materials but can be summed up fairly easily.
美国联邦法规21 CFR 101.22对天然香料进行了定义。本法规中的关键定义是“
术语天然香料或天然调味剂是指…任何…植物材料，肉类，…，鸡蛋，乳制品或其发酵产品，其在食品中的重要功能是调味....
”这个定义确定了许多种类的天然原材料和生产原材料的一些方法，但可以相当容易地总结。
Natural Flavors Definition (USA) 天然香料定义（美国）
Under US regulations, natural flavors are flavors derived from natural raw materials that contain no artificial constituents. Artificial within the meaning of this regulation is synthetic or petrochemical. The raw materials that meet the natural definition include all animal products such as meat, egg and dairy. It also includes all botanical sources and all microbiological sources, including fermentation products. As long as the raw material source is not mineral or petrochemical, the source is considered natural.
根据美国法规，
天然香料是指从不含人工成分的天然原料中提取的香料
。
本条例所称人工是指合成的或石化的
。符合自然定义的原材料包括所有动物产品，如肉、蛋和奶制品。它还包括所有植物来源和所有微生物来源，包括发酵产品。
只要原料来源不是矿物或石化，就被认为是天然的
。
Note also, that products from Genetically Modified Organisms (GMO) including those modified using synthetic biology
1
are considered natural. GMO raw materials do not impact the natural status of flavors.
还要注意的是，
来自转基因生物(GMO)的产品，包括那些使用合成生物学进行改造的产品，都被认为是天然的
。
转基因原料不会影响香精的天然状态
。
There is little restriction on manufacturing processes in declaring flavors as natural. For example, isolation of natural flavors through chemical transformation by inorganic catalysts meets the US natural flavor requirement. As an example, 2-methyl-2-pentenoic acid (FEMA# 2923) manufacturing by the base-catalyzed condensation of propionaldehyde isolated from fusel oil is considered natural. In this case, the raw material (fusel oil) is considered a natural raw material since it is the by-product of alcohol fermentation. The intermediate is isolated by distillation, a physical process, then undergoes chemical transformation via a catalyst, followed by oxidation by heating in air, and finally further purification by distillation.
在宣称香料为天然香料的生产过程中，几乎没有什么限制。例如，通过无机催化剂的化学转化分离天然香料，就满足了美国对天然香料的要求。例如，
从杂醇油中分离的丙醛通过碱催化缩合生产2-甲基-2-戊烯酸(FEMA# 2923)被认为是天然的
。在这种情况下，原料(杂醇油)被认为是天然原料，因为它是酒精发酵的副产品。中间体通过蒸馏分离，这是一个物理过程，然后通过催化剂进行化学转化，接着在空气中加热氧化，最后通过蒸馏进一步提纯。
Figure 1.
Synthesis of natural 2-methyl-2-penenoic acid
图1 天然2-甲基-2-戊烯酸的合成
Analytical Verification of US Natural Flavors 美国天然香料的分析验证
Analytical verification of US natural flavors is most commonly done by carbon 14 (14C) isotopic analysis. 14C is formed in the upper atmosphere by interaction with cosmic rays. The atmospheric concentration of 14C (primarily in carbon dioxide) is about one part per trillion (ppt). Atmospheric CO
2
is absorbed by plants which then take on a 14C concentration equal to atmosphere 14C. This concentration is transferred to any other organism in the food chain, and ultimately to any products derived from the food chain – such as natural flavors. Since 14C has a half-life of 5,730 year, any petroleum-based raw materials would be completely depleted of 14C and the lack of 14C indicates a material of synthetic origin. 14C analysis is often reported as percent modern carbon (pmc), indicating the degree to which 14C is depleted and thus the degree to which synthetic raw materials are used.
美国天然香料的分析验证最常用的方法是碳14 (14C)同位素分析
。14C是在上层大气中与宇宙射线相互作用而形成的。大气中碳的浓度(主要是二氧化碳)大约是万亿分之一(ppt)。大气中的二氧化碳被植物吸收，然后植物吸收的碳浓度等于大气中的碳浓度。这种浓度转移到食物链中的任何其他生物体，并最终转移到食物链中的任何产品，例如天然香料。
由于14C的半衰期为5730年，任何以石油为基础的原材料都将完全耗尽14C，缺乏14C表明材料的合成来源
。14C分析通常报告为现代碳百分比(pmc)，
表明14C耗尽的程度，从而表明使用合成原料的程度
。
In analyzing 14C results one must be aware of certain factors, however. Atmospheric 14C has not been constant in the last several decades. Above-ground nuclear testing artificially increased the 14C concentration in the atmosphere, peaking in 1963. Materials derived from older natural sources, such as massoia lactone (FEMA# 3744), which is derived from the bark of massoia trees, could show an unexpectedly high 14C concentration versus the current atmospheric concentration. Since the bark could be decades hold, the massoia lactone may have been isolated at a time when the 14C concentration was higher than today. Additionally, in some regions with heavy fossil fuel use, and poor atmospheric circulation, the local 14C level may be lower than expected. Although it is possible also, to add a 14C source to a flavor in order to give a false positive for natural, this type of adulteration is very difficult and expensive to do. Overall 14C analysis represents one of the best tools for authenticating natural raw materials were used in producing the flavor.
然而，在分析14C结果时，必须意识到某些因素。在过去的几十年里，大气中的碳含量并不是恒定的。
地面核试验人为地增加了大气中的碳- 14浓度，在1963年达到峰值
。从较老的天然来源中提取的材料，如从马尾松树皮中提取的马索亚内酯(FEMA# 3744)，与目前的大气浓度相比，可能显示出意想不到的高14C浓度。
由于树皮可以保存几十年，马索亚内酯可能是在14C浓度高于今天的时候被分离出来的
。此外，在一些大量使用化石燃料和大气环流不良的地区，当地的14C水平可能低于预期。
虽然也有可能在香精中添加14C源，以产生天然的假阳性，但这种类型的掺假是非常困难和昂贵的
。总的来说，
14C分析是鉴定用于生产香精的天然原料的最佳工具之一
。
EU Natural Flavors 欧盟天然香精香料
Natural flavors are defined in the EU in regulation (EC) 1334/2008. This regulation defines three criteria for natural flavor; 1) they must be “obtained by appropriate physical, enzymatic or microbiological processes”, 2) they must be “from material of vegetable, animal or microbiological origin”, and 3) they must “correspond to substances that are naturally present and have been identified in nature.”
天然香料在欧盟法规(EC) 1334/2008中有定义
。该法规定义了天然香料的三个标准;1)
它们必须“通过适当的物理、酶促或微生物过程获得”
，2)
它们必须“来自植物、动物或微生物来源的材料”
，以及3)
它们必须“对应于自然存在并已在自然界中识别的物质”
。
The second criteria is in practice the same as the US requirement of natural source raw material. Like the US, GMO is acceptable for raw materials for natural flavor declarations. Unlike the US, however, the EU requires that natural flavors be manufactured only by traditional food preparation processes. This includes such processes as heating/cooking, physical processes like cutting, grinding, or pressing, physical separations like distillation or recrystallization, solvent extraction, enzymatic processes, and fermentation. The EU precludes the use of synthetic and inorganic catalysts in manufacturing natural flavors. Other chemical catalysts such as singlet oxygen, ozone, or UV radiation are similarly not allowed when manufacturing natural flavors. As an example, natural flavors can be purified by adsorption onto activated carbon, but the adsorption cannot be used to facility a chemical transformation. So the conversion of citronellal (FEMA# 2307) to isopulegol (FEMA# 2962) on silica gel is not acceptable for natural flavors. The EU does allow for the use of natural organic acids or bases to improve the yield of natural flavors, so long as they are not required for the chemical transformation.
第二个标准实际上与美国对天然原料的要求相同。与美国一样，天然香料声明的原材料中也可以使用转基因。
然而，与美国不同的是，欧盟要求天然香料只能通过传统的食品制备工艺生产
。
这包括加热/烹饪等过程，切割、研磨或压榨等物理过程，蒸馏或重结晶等物理分离过程，溶剂提取，酶促过程和发酵
。
欧盟禁止在生产天然香料时使用合成和无机催化剂。其他化学催化剂，如单线态氧、臭氧或紫外线辐射，在生产天然香料时同样是不允许的
。例如，
天然香料可以通过吸附到活性炭上来纯化，但这种吸附不能用于化学转化
。因此，
香茅醛(fema# 2307)在硅胶上转化为异戊二醇(fema# 2962)对于欧盟天然香料是不可接受的
。
欧盟允许使用天然有机酸或碱来提高天然香料的产量，只要它们不需要进行化学转化
。
An example of an acceptable EU natural flavor manufacturing process is the manufacture of methyl cyclopentalone (FEMA# 2700) from sugarcane. Sugarcane is crushed and ground into a pulpy mass called bagasse. Upon heating, a sugary organic-chemical mix can be isolated (distilled). Yeast (
saccharomycetaceae
) is then used to yield fermentation products that are isolated by distillation, including the caramellic/sweet/coffee tasting methyl cyclopentenolone. Here only physical and microbiological processes are used, so the end material is considered natural in the EU.
可接受的欧盟天然香料制造工艺的一个例子是
从甘蔗中生产甲基环戊烯醇酮
(FEMA# 2700)。
甘蔗被碾碎并磨成一种叫做甘蔗渣的糊状物质。加热后，可以分离出含糖的有机化学混合物(蒸馏)。然后使用酵母(酵母菌科)产生通过蒸馏分离的发酵产物，包括焦糖/甜味/咖啡味的甲基环戊烯醇酮
。这里只使用物理和微生物过程，因此最终材料在欧盟被认为是天然的。
Figure 2.
Synthesis of natural methyl cyclopentenolone
图2 天然甲基环戊烯诺酮的合成
Identified in Nature 在天然中被识别
In addition to the raw material and manufacturing process requirements in the EU regulations, the EU also states that natural flavors must “correspond to substances that are naturally present and have been identified in nature.” The latter part of this requirement, “identified in nature” can be verified by comparing the flavoring substance to literature references. Fenaroli’s Handbook of Flavor Ingredients is a good resource for finding natural occurrence as is The Good Scents Company website (thegoodscentscompany.com). For materials that may have optical or geometric isomers “correspond to substances that are naturally present” would include all isomers in any ratio as long as all the isomers are found in nature or are known to form through natural processes when isolated. For example, δ –decalactone (FEMA# 2361) occurs naturally in both the S(-) enantiomer (96.6% EE in raspberries) and R(+) (94.0% EE in peaches). Because both enantiomers are found in nature, a flavor of exclusively S or R or any combination including racemic mixtures meets the “identified in nature” requirement.
除了欧盟法规中的原材料和制造工艺要求外，欧盟还规定天然香料必须“与天然存在并在自然界中被识别的物质相对应”
。这一要求的后一部分，“在自然界中识别”可以通过将调味物质与文献进行比较来验证。
Fenaroli的《香料成分手册》是一个很好的寻找天然成分的资源，好香味公司的网站(thegoodscentscompany.com)也是。
对于可能具有光学或几何异构体的材料，
“对应于自然存在的物质”将包括任何比例的所有异构体，只要所有异构体都是在自然界中发现的，或者在分离时已知是通过自然过程形成的
。例如，
δ -癸内酯(FEMA# 2361)天然存在于S(-)对映体(树莓中EE含量为96.6%)和R(+)对映体(桃子中EE含量为94.0%)中
。
因为这两种对映体都是在自然界中发现的，所以只有S或R的风味或任何包括外消旋混合物的组合都符合“在自然界中识别”的要求
。
Ammonium, sodium, potassium and calcium salts of flavors as well as chlorides, carbonates and sulfates are considered “identified in nature” as long as the parent flavor is identified in nature. For example, methyl ethyl pyruvic acid (FEMA# 3870) naturally occurs in asparagus, cocoa, and some cheeses. Sodium 3-methyl-2-oxovalerate (FEMA# 3870) could be considered natural, even though it is not identified in nature, as long as it meets the other criteria.
铵盐、钠盐、钾盐和钙盐以及氯化物、碳酸盐和硫酸盐都被认为是“在天然中被识别的”，只要母体风味在天然中被识别。例如，
甲基乙基丙酮酸(FEMA# 3870)天然存在于芦笋、可可和一些奶酪中
。
3-甲基-2-氧戊酸钠(FEMA# 3870)可以被认为是天然的，即使它没有在自然界中被发现，只要它符合其他标准
。
Analytical Verification of EU Natural Flavors
欧盟天然香料的分析验证
Because EU natural flavors have three criteria, analytical verification can be very difficult. 14C analysis can be used to verify the raw material source is natural, but it is very difficult to confirm the material was manufactured using an acceptable, traditional process. Several methods are used to discern the manufacturing process, but they all have their limitations.
由于欧盟天然香料有三个标准，分析验证可能非常困难。
14C分析可用于验证原料来源是天然的，但很难确认该材料是使用可接受的传统工艺制造的
。有几种方法用于辨别制造过程，但它们都有其局限性。
Chiral Analysis 手性分析
Since some chiral materials are found in nature in only one enantiomer, chiral analysis can be used to verify the material meets the identified in nature criteria. If other enantiomers are found in nature, however, any enantiomeric combination is acceptable. Since enzymatic methods can result in enantiomeric ratios not found in nature, and materials may racemate over time, particularly if heated, like during a distillation/purification, identification of a racemic mixture is not sufficient to declare a material is not natural.
由于某些手性材料在自然界中只存在于一种对映体中，因此可以使用手性分析来验证该材料是否符合自然界中确定的标准。然而，如果在自然界中发现其他对映体，则任何对映体组合都是可以接受的。
由于酶促方法可以产生自然界中没有的对映体比例，并且材料可能随着时间的推移而外消旋，特别是在加热的情况下，如在蒸馏/纯化过程中，外消旋混合物的鉴定不足以声明材料不是天然的
。
Fingerprint Analysis 指纹图谱分析
Some synthetic methods yield known impurities indicative of the synthetic process. For example, when mineral acids are used to convert 2-methyl butanol (FEMA# 3998) to 2-methylbutyric acid (FEMA# 2695) the reaction also yields 2-hydroxy-2-methylbutyric acid. Presence of 2-hydroxy-2-methylbutyric in 2-methylbutryic acid is therefore indicative of a process not acceptable as natural in the EU. Although the fingerprint analysis is a good method for a few well-known synthetic processes it is limited to only those known reaction schemes.
有些合成方法产生已知的杂质，表明合成过程。例如，
当使用无机酸将2-甲基丁醇(FEMA# 3998)转化为2-甲基丁酸(FEMA# 2695)时，该反应也会产生2-羟基-2-甲基丁酸
。因此，
在2-甲基丁酸中存在2-羟基-2-甲基丁酸表明该过程在欧盟是不可接受的
。虽然指纹分析对一些已知的合成过程是一种很好的方法，但它仅限于那些已知的反应方案。
Site-Specific DNMR 位点特异性DNMR
Some natural processes result in a known hydrogen-deuterium ratio at specific molecular sites. Determination of naturalness, however, can be quite challenging. Different acceptable natural manufacturing methods such as extraction, fermentation, or enzymatic conversion and different natural raw materials can result in a wide range of hydrogen-deuterium ratios. This method is therefore good for a positive test; verifying a known natural method was used, but a negative result may not be definitive for discounting naturalness.
一些天然过程会在特定的分子位置产生已知的氢氘比。然而，确定天然程度是相当具有挑战性的。
不同的可接受的天然制造方法，如提取、发酵或酶转化，以及不同的天然原料，可以产生大范围的氢氘比
。因此，这种方法对阳性测试很好；使用了已知的天然方法进行验证，但否定结果可能不能确定是否为天然性。
Stable Isotope Ratio Analysis (SIRA) 稳定同位素比例分析
Stable isotope ratio analysis is similar to site-specific DNMR in that is evaluates the stable isotopic ratio of flavor molecules. Atmospheric oxygen, for example, has a known, stable isotopic ratio. Oxidation of alcohols to acids using mineral acids results in an oxygen isotopic ratio that differs from the natural atmospheric ratio. Like DNMR, SIRA has similar shortcomings. Different, acceptable manufacturing methods can result in different isotope ratios. Fermentation, for example, may scramble oxygen isotope ratios. Like DNMR, SIRA is good for positive results, showing a stable isotope ratio resulted from a known natural manufacturing method, but negative results may not be definitive.
稳定同位素比分析类似于位点特异性DNMR，它是评估风味分子的稳定同位素比
。例如，大气中的氧就有一个已知的稳定同位素比。利用无机酸将醇氧化为酸，产生的氧同位素比率与天然大气比率不同。和DNMR一样，SIRA也有类似的缺点。不同的、可接受的制造方法可以产生不同的同位素比率。例如，
发酵可能会扰乱氧同位素比率
。与DNMR一样，SIRA有利于阳性结果，显示由已知的天然制造方法产生的稳定同位素比率，但阴性结果可能不是决定性的。
EU Natural Flavor Summary 欧盟天然香料小结
The EU definition of natural flavors is stricter than that in the US. As a result, EU natural flavors meet the US requirement, but the reverse is not necessarily true. EU natural has requirements on the manufacturing method as well as the raw material origin. Confirmation of the natural method can be very difficult and all the analytical methods have their shortcomings. Additionally the EU requires that materials declared as natural flavors be identified in nature. This excludes some flavors such as vanillyl butyl ether (FEMA# 3796) which is produced from the fermentation of vanillyl alcohol (FEMA# 3737) but there is no identified natural occurrence of vanillyl butyl ether.
