|
葡
萄
醋
Laura
Dallagiovanna, Valeria Mazzoleni
Istituto
di Enologia e Ingegneria alimentare, Università Cattolica del Sacro
Cuore
29100
– Piacenza (Italy)
E-mail:
valeria.mazzoleni@pc.unicatt.it
人类很早就知道食醋对人体的益处，从出现时起醋就不仅用于调味，而且还用于医疗和抗污染变质的目的。
醋一直被当作食品保鲜剂，目前它被广泛用于泡菜的生产，并成为很多调味汁和色拉酱的成份。醋的有效保鲜作用得益于其中所含的醋酸，在不低于6％（V/V）的浓度下，由于其未解离分子对微生物（特别是细菌和酵母菌）的毒性，强烈抑制了微生物所引起的食品败坏。
近年来一些医学专家特别强调了醋在饮食中的重要性，它有利于食品中某些营养成分的稳定。葡萄醋中的多酚类物质能够通过他们的清除作用，有助于维生素C和E的稳定，这两种维生素可以对抗细胞在生物化学过程中产生的有害自由基的作用。因此，与葡萄酒相似，醋作为地中海饮食的一部分，对一些慢性的变质病原菌起抑制作用，达到对这类饮食的保护作用。
还有很多关于醋中的酚类成份具抗癌作用（原位与体外）的报道，无论是在消化道水平上，还是在组织水平上，都表现出效果。
生产与消费
尽管葡萄醋在全世界都生产和消费，却很难给出关于产量的精确信息，原因是大量的葡萄醋仍然是家庭产品。欧洲以葡萄酒生产食醋，尤其在酿造大国，如意大利、法国、西班牙和希腊等更是如此，其它国家的食醋生产主要以其它各种农产品（大麦芽，水稻芽、苹果酒，乙醇）生产的初级酒精为原料。意大利每年生产大约6万吨醋，绝大多数来源于葡萄酒，是世界领先的葡萄醋生产国。德国作为欧洲领先的食醋生产者，年产量达13万吨，主要以酒精为原料。其它国家如中国和日本，食醋均以稻米为原料。
意大利的食醋生产非常分散，虽然在北部地区相对集中，这反映了饮食传统的地理特点。
意大利的食醋消费量是欧洲最低的国家之一：年均消费据估计大约为每人1升
（低于丹麦、比利时、德国和法国的每人每年2升或更多的水平），并呈现每年1％缓慢增长的趋势。日常用醋以1升的玻璃瓶包装，品质更高的食醋为半升的瓶装。
近来消费者的喜好发生了一些变化，他们趋向于购买来自D.O.C.和D.O.C.G.葡萄酒产区的优质葡萄醋或加香醋，其它的趋势还包括消费者喜欢以白葡萄酒制成的色泽为禾草黄色的醋，人们认为这种醋比用红葡萄酒生产的‘红醋’更为柔和。
分类
根据意大利的立法‘醋’特指葡萄酒经醋酸发酵所获得的产品。目前，根据欧盟的指示，意大利的立法不仅允许将来自葡萄酒的产品命名为葡萄醋，而且对来自其它原料（如苹果等）的产品，根据原料命名为“XX醋”。依据法律，醋的酸度不得低于6％（以醋酸重量、体积比计），同时酒精残量不得高于1.5％（体积百分比）。各种葡萄醋的分类如下：
◇
葡萄醋：
来自于低质葡萄酒、稍发生酸化的葡萄酒或酒精度低于8％（体积百分比）的葡萄酒。这类葡萄醋的酒精残量很低（0.2-0.3%），酸度为6％。
◇
优质葡萄醋：产自优质葡萄酒，其原料包括D.O.C.和D.O.C.G.级的极优质葡萄酒。通常这类葡萄醋要在木桶或不锈钢容器中经历一个成熟过程。其酒精残量高（0.5-1.0%），酸度大约为7％。
◇
加香葡萄醋：产自优质葡萄醋，其中浸渍了芳香草本植物或香料（如：龙蒿、百里香、胡椒等。）
◇
无色葡萄醋：只用于生产泡菜、沙司和色拉酱。
◇
特殊醋：这类醋中最富盛名的种类是产自Modena
和
Reggio Emilia地区的传统香醋，它来自于葡萄的酒精发酵和醋酸发酵，葡萄可经部分发酵或火力加热浓缩。
用于食醋原料的葡萄酒的特征
用于生产食醋的白葡萄酒或红葡萄酒可以是好酒或挥发性酸度高于市售葡萄酒标准的葡萄酒（根据欧盟的规定其限度为白葡萄酒1.08g/L醋酸，红葡萄酒为1.20g/L），原料酒可以为澄清或轻微浑浊状态。此外，葡萄酒还必须干（不含糖）、无抗菌剂，各项金属离子指针不得高于法定的标准。此外，还不能含有过高的单宁或酚类物质。在葡萄醋生产过程开始前葡萄酒需用水进行稀释，以达到理想的酒精含量，这意味着对普通醋为7－9％，对优质葡萄醋则稍高一点。
醋酸发酵
醋酸发酵的基本反应需要醋酸菌的存在，反应如下：
乙醇＋氧气
→
醋酸＋水
氧气和温度是反应的限制因子。Acetobacter
和
Gluconobacter属的醋酸细菌在30℃表现最大活力，处于微酸的pH值下，当酒精含量在7－10％之间时，它们对二氧化硫的存在非常敏感。
生产技术
a) 酸化
生产工艺为葡萄酒通气，以达到最优醋酸化速度，这个过程严格依赖于葡萄酒中氧的含量。
一种最近被重新应用于优质葡萄醋生产的传统方法，前瞻到“滴流过程”trickling
process）的应用，它在木桶的低端设置隔架，充填多孔性物质（刨花，葡萄梗，玉米芯），而醋酸菌就在这些多孔性物质上生长（图1）
葡萄酒从顶端灌入，经多孔性物质过滤、被收集，在容器的底部部分发酵。液体随后进行循环直至达到期望的酸度。容器永远不完全倒空，所以醋的残留总可以启动新的醋酸化循环。由于较长的醋酸化时间和显著的产量损失（大约20％）－这与挥发性成份特别是乙醇的蒸发有关，这个表面过程有其不足之处。此外，由于容器中碎屑分布的不均一，以及细菌产生的粘性物质，系统可能被堵塞，需要阶段性地进行清理，因此造成昂贵的系统保养开销。积极的方面是产品相对澄清，生产出的醋只需要相当简单的稳定处理。
一套曾经得到极为广泛使用的可以上溯至40年代的系统，被称为“淹没菌株醋酸化”（submerged
culture acetification），在这个系统中细菌存在于液体中，得益于强制注入的空气在微生物、葡萄酒喝氧气之间创造出的紧密接触。利用这个体系可以获得高产（95－98％）、更快的醋酸化过程和稳定的产品质量保证（图2）。这个系统的一个缺点是所获得的产品较浑浊，需要一个较复杂的稳定过程。此外，由于充入的用于加速生产过程的氧气所造成的氧化，用这种方法生产出的葡萄醋感官品质和化学特征较差。
最近，为了降低贮藏成本，业界已趋向于通过一种“两步发酵法”（two
stage fermentation process）生产高酸含量的醋，产品的醋酸度高于15％。在第一步我们让细菌生长并进行部分醋酸化；在第二步细菌的繁殖降低直至停止，而醋酸的生产仍然进行直至达到期望的酸度。
我们还有一些醋酸化系统处于试验阶段，比如：一个使用发酵塔的连续醋酸化体系，无内部部分强化通气。更快的醋酸化还可以通过增加生物反应器中的细菌浓度来达到：如使用细胞固定化技术或细胞回收循环。
b)
澄清与装瓶
由工业法生产出的葡萄醋是浑浊的，因为其中含有呈悬浮态的粘质、纤维类物质、蛋白质和细胞等。这意味着需要一个稳定的过程使葡萄醋得到澄清并成熟。
各种处理包括：
＞
自然澄清，将醋静置于容器中，然后通过倒桶去除固体沉淀；
＞
通过过滤或离心的机械进行澄清；
＞
通过添加佐剂进行澄清；
＞
物理稳定法如进行巴斯德处理或冷却处理；
＞
去除金属离子；
＞
用活性炭脱色，这种方法只用于生产无色葡萄醋。
葡萄醋的澄清方法从过滤系统到澄清剂都与葡萄酒的稳定处理非常相似。在过去的几年中膜过滤设备逐渐被葡萄醋行业所了解和采用。这些设备不仅能够使葡萄醋达到微生物稳定，而且能够同时减少化学杀菌剂的使用。
为提高感官品质，优质葡萄醋可在木桶中经历一个为期6－8个月的陈酿成熟过程，然后再于不锈钢容器中完成6－8个月的进一步成熟。
装瓶是生产的最后步骤。它非常重要，因为在包装瓶中葡萄醋的成熟过程将继续进行，并最终在基本还原的条件下结束。
葡萄醋的成份
葡萄醋是澄清的液体。其色泽可以为淡黄色、金黄色、桃红色或红色，表现既刺激又宜人的香气以及辣酸的口感。
葡萄醋与葡萄酒的成份相似（表1），少量的不同来源于醋酸发酵过程中所形成的物质，如醋酸和醋醛，醋的香气和典型的刺激性口感主要来源于醋酸的存在。葡萄醋的柔和性则有赖于来自葡萄酒的甘油的存在，其含量在2－6g/L之间。
含氮组分以一组自由氨基酸为代表，而多酚类物质（单宁、花色素苷和黄酮类物质）来自葡萄酒，在葡萄醋中可以被检出，数量与所采用的澄清工艺有关。
葡萄醋的品尝
通过感官分析我们可以对葡萄醋的典型性和质量进行评判。然而，与葡萄酒的品尝不同，葡萄醋的品尝要困难得多。原因在于葡萄醋强烈的风味使品尝变得困难，而且安排一个品尝小组也比较困难。
在过去的几年中一些研究者，基于定量描述性分析的原则以及在发酵领域所获得的经验，如图3所示，建立起了一种非结构描述表（香气轮图）。
[Translated
by 马会勤
-Carlo Queruli]
图一
FIGURE
1 - Plan of the equipment operating with surface process
(Trickling Process)
A
grate; B porous material; C circulating pump; D squirt gun; E water
refrigerant; F condenser
图二
FIGURE
2 – Plan of the equipment for the production of vinegar with
submerged culture (Acetator Frings)
A
Wine tank; B Acetator; C Vinegar tank
a
aerator, b defoamer, c cooler, d automatic detector of alcool
degree.
图三
FIGURE
3 - Unstructed sheet proposed for the sensory analysis of red
and white vinegars.
The
descriptors between brackets refer to the white vinegar.
Descriptors:
1)
Clarity
2)
Colour intensity
3)
Red (Straw yellow)
4)
Yellow (Gold yellow)
5)
Brick red (Amber yellow)
6)
Odour intensity
7)
Odour pungency
8)
No odour defects
9)
Floral note
10)
Fruity
11)
Vinous
Character (Vegetative odour)
12)
Balance
of odour
13)
Balance of taste
14)
Sapidity
15)
Taste persistence
↑TOP↑
WINE
VINEGAR
Laura
Dallagiovanna, Valeria Mazzoleni
Istituto
di Enologia e Ingegneria alimentare, Università Cattolica del Sacro
Cuore
29100
– Piacenza (Italy)
E-mail:
valeria.mazzoleni@pc.unicatt.it
The
beneficial action of vinegar on the human body has long been known,
right since it was used not only as a food
but also for medicinal and anti-contamination purposes.
Vinegar
has always been used as a preserving agent for food products and at
the moment it is widely used in the industry for pickling and as an
ingredient in various sauces and dressings. The preserving action of
vinegar owes its success to the fact that the acetic acid it
contains, if at a level of at least 6% (v/v), stops microbic
alterations in so much as that its undissociated molecule is toxic
for the micro organisms (particularly bacteria and yeasts).
In
recent years some medical researchers have highlighted the
importance of vinegar in the diet, in that it favours the
stabilisation of certain nutritional components in food. The
polyphenols contained in wine vinegar can aid, through their
scavenger effect, the stabilisation of the vitamins C and E, which
fight the harmful action of free radicals deriving from biochemical
action of the cells.
In
this way, like wine, vinegar is part of the Mediterranean diet,
playing a protective role in this type of diet as far as regards
some chronic degenerative pathologies.
There
have also been extensive descriptions of the anti-cancerous effects
(in vivo and in vitro) of many phenolic compounds present in
vinegar- effects that show themselves at a gastrointestinal level or
at peripheral tissue level.
Production
and Consumption
Although
wine vinegar is produced and consumed all over the world, it is hard
to give precise information on
the quantity produced, in that a large amount of vinegar is
still fruit of homemade production. Vinegar made from wine is
produced in Europe, particularly in the countries with a high
oenological production, such as Italy, France, Spain and Greece,
whilst in other countries it is produced from alcoholic primary
ingredients of a varied nature (barley malt, rice malt, cider, ethyl
alcohol…….). Italy produces about 600.000 hl of vinegar per
year, the vast majority from wine and it is the world’s leading
producer of wine vinegar. Germany, Europe’s leading vinegar
producer, with a production of over 1.300.000 hl/year, mainly uses
ethyl alcohol as primary ingredient. In other countries such as
China and Japan, vinegar is produced from rice.
The
Italian vinegar industry is very fragmented, albeit more
concentrated in the northern regions, something that reflects the
geographical distribution of food traditions.
As
far as consumption is concerned, Italy is rates as one of the lowest
consumers in Europe: the annual Italian vinegar consumption is
assessed to be about one litre per head (against 2 litres or more
per head in countries such as Denmark, Belgium, Germany and France)
with a very slight increasing tendency of about l % per year. The
most commonly used vinegars is packed in one-litre glass bottles,
while higher quality vinegar in half-litre bottles.
However,
consumer preferences have been changing recently and they are
tending to go either for quality vinegars produced from D.O.C. and
D.O.C.G. wines or for aromatised vinegars. There is also a
preference toward straw vinegars (from white wine), which are
considered to be suppler than red ones (from red wine).
Classification
According
to Italian legislation the term “vinegar” is reserved to the
product obtained from the acetic fermentation of wine. Currently,
according to the Community Directives, the Italian legislation also
allows not only the denomination
“wine vinegar” for products deriving from wine but also
the denomination “……. vinegar ” preceded by the substance of
origin, for vinegars coming from other primary ingredients
(e.g. apples). By
law, the vinegars must not have an acidity level lower than 6 %
(expressed in w/v of acetic acid) nor residual alcohol higher than
1.5 vol. %.
The
various types of wine vinegars are:
◇
Common
Vinegar:
produced from acetification of low quality or slightly altered wines
or with an alcohol degree lower than 8 vol. %. These vinegars have a
very low alcohol residue (0.2-0.3 vol.%) and an acidity of 6%.
◇
Quality
vinegar:
produced from sound, good quality wines, including D.O.C. or D.O.C.G.
wines. Generally these vinegars undergo a maturation process in wood
and stainless steel containers. They have a high alcohol residue
(0,5-1,0 vol.%) and an acidity of around 7%.
◇
Aromatised
Vinegar:
produced from quality vinegar, they are infused in aromatic herbs or
spices (e.g. estragon, thyme, pepper) .
◇
Colourless
Vinegar:
only used for production of pickles, sauces and dressings.
◇
Special
Vinegar:
in this range of vinegars the most prestigious types are traditional
Balsamic Vinegars from Modena or Reggio Emilia, obtained from
alcoholic and acetic fermentation
of grapes, possibly partially fermented or concentrated by direct
fire.
Characteristics
of wine used for vinegar production
White
or red wine used for the production of vinegar may be sound wine,
wine with a volatile acidity higher than the level permitted for
wines ready for the market (according to Community Regulation the
limit is 1,08 g/l of acetic acid for white wines and 1,20 g/l for
red ones) and it can be clear or slightly cloudy. In addition it
must be dry, free of antimicrobial agents, not contain any metals
above limits permitted by the law and must not be particularly rich
in either tannic or phenolic substances. Before vinegar making
process begins, the wine needs to be diluted with water until it
reaches the ideal degree of alcohol, which means between 7 and 9
vol. % for common vinegars and a slightly higher level for quality
vinegars.
Acetic
Fermentation
The
fundamental reaction of acetic fermentation, that needs the presence
of acetic acid bacteria, is as follows:
Ethanol
+ Oxygen
Acetic Acid + Water
The
oxygen required, together with the temperature, is a limitative
factor of the reaction. The acetic acid bacteria, between the genera
Acetobacter and Gluconobacter,
shows optimum activity at 30°C,
at a pH level slightly acid, at an alcoholic degree between 7
and 10 vol.%; they are very sensitive to the presence of sulphur
dioxide.
Production
Technology
a)
Acetification
The
production technology exploits the aeration of wine, with the aim to
optimise the speed of acetification, which depends very strictly on
the quantity of oxygen present in the wine.
A
traditional method, which has recently come back into use for the
production of quality vinegars, foresees the use of a trickling process based on the use of a wood tank fitted with a
grate on the lower part and filled with porous material (wood
shavings, grape stalks, corn cobs) where the acetic acid bacteria
growth (Figure 1). The wine, fed from the upper part, percolates
through the porous material and is collected, partially fermented,
on the bottom of the tank. The liquid is then recycled until the
desired acidity is obtained. The tank is never completely emptied,
so that the vinegar residue can always start up a new acetification
cycle. This surface process has its drawbacks due to the fact that
we have long acetification times and a marked product loss (about
20%) – this is linked to the evaporation of volatile constituents,
in particular ethanol. Furthermore, due to the uneven distribution
of chippings in the tank and the accumulation of mucilaginous
substances produced from the bacteria, the system may get clogged
and it will need to be periodically cleared and undergo costly
maintenance service. The positive aspect is that the vinegar
produced is relatively clear and requires more simple stabilising
operations.
A
system very widely used, which dates back to the 40’s, is the submerged
culture acetification, where the bacteria are present into the
liquid, thanks to a forced insufflation of air that creates a close
contact between microorganisms, wine and oxygen. With this process
we get high yields (95-98%), faster acetification and the assurance
of a constant product (Figure 2). One of the negative aspects of the
system is that the product obtained is cloudy and needs to undergo
more complex stabilisation. What is more, vinegars produced in this
way have inferior sensory and chemical characteristics due to the
oxidation caused by the high quantity of air introduced to speed up
production times.
Recently,
in order to reduce storage costs, the industry has gone towards the
production of vinegars with a high degree of acidity by means of a two
stages fermentation process, which produces vinegars with
acidities above 15 %. In the first stage we have bacteria growth and
a partial acetification. In the second stage bacteria multiplication
slows down until it stops. However, the production of acetic acid
continues until the acidity desired is reached.
We
still have some acetification systems in experimental phase: for
example a system of continuous acetification with the use of fermenting
towers free of internal parts with forced aeration. Faster
acetifications can also be obtained by increasing the bacteria
concentration in the bioreactor: cell immobilization or cell-recycle.
b)
Clarification and bottling
The
vinegar produced by industrial methods is cloudy because it contains
suspensions of mucilage, cellulosic substances, protein and cells.
This means we need to have a stabilization phase in which the
vinegar can be clarified and matured.
Various
types of treatments are:
◇ Spontaneous
clarification, which is obtained by letting the vinegar rest in tank
and then removing solid matter by mean of a racking;
◇ Mechanical
clarification by filtering or centrifuging;
◇ Fining
by means of adjuvants;
◇ Physical
stabilisation as pasteurisation or refrigeration;
◇ Removal
of metals;
◇ Decolourising
with activated carbon, only for the production of colourless
vinegars.
The
clarification methods, the filtering systems and the fining agents
are very similar to those used in wine stabilization. In the last
few years membrane filters were introduced in the vinegar industry.
These filters allow the microbial stability of the vinegar and, at
the same time, a reduction of chemical antiseptic agents.
To
improve their sensory characters, the quality vinegars can undergo maturation
in wood casks for 6-8 months and then carry out further maturation
period in stainless steel containers for 6-8 months.
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