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Liquid smoke is a water-soluble yellow to red liquid used as a
flavoring A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive that is used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of ...
as a substitute for cooking with wood smoke while retaining a similar flavor. It can be used to flavor any meat or vegetable. It is available as pure condensed smoke from various types of wood, and as derivative formulas containing additives.


History

Pyrolysis Pyrolysis is a process involving the Bond cleavage, separation of covalent bonds in organic matter by thermal decomposition within an Chemically inert, inert environment without oxygen. Etymology The word ''pyrolysis'' is coined from the Gree ...
or thermal decomposition of wood in a low oxygen manner originated prehistorically to produce
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ca ...
. Condensates of the vapors eventually were made and found useful as preservatives. For centuries, water-based condensates of wood smoke were popularly called " wood vinegar", presumably due to its use as food
vinegar Vinegar () is an aqueous solution of diluted acetic acid and trace compounds that may include flavorings. Vinegar typically contains from 5% to 18% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting ...
. In 1658, Johann Rudolf Glauber outlined the methods to produce wood vinegar during charcoal making. Further, he described the use of the water insoluble tar fraction as a wood preservative and documented the freezing of the wood vinegar to concentrate it. Use of the term " pyroligneous acid" for wood vinegar emerged by 1788. In the United States, in 1895, E. H. Wright inaugurated the era of commercial distribution of pyroligneous acid under a new name, liquid smoke. Among Wright's innovations were the standardization of the product, marketing and distribution. Wright's Liquid Smoke, since 1997 owned by B&G Foods, and its modern-day successors have always been the subject of controversy about their contents and production, but in 1913, Wright prevailed in a federal misbranding case. Case judge Van Valkenburg wrote: Historically, all pyroligneous acid products, Wright's product and many other condensates have been made as byproducts of charcoal manufacturing, which was of greater value. Chemicals such as
methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...
,
acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...
and
acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...
have been isolated from these condensates and sold. With the advent of lower cost
fossil fuel A fossil fuel is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or microplanktons), a process that occurs within geolog ...
sources, today these and other wood derived chemicals retain only small niches. Today there are many manufacturing locations around the world, most of which pyrolyze wood primarily to generate condensates which are further processed to make hundreds of derivative products. These are now referred to less as liquid smoke products, and instead as smoke flavorings, smoke flavors, and natural condensed smoke.


Production

The condensed products from the
destructive distillation Destructive distillation is a chemical process in which decomposition of unprocessed material is achieved by heating it to a high temperature; the term generally applies to processing of organic material in the absence of air or in the presence o ...
of wood are called "liquid smoke" or "pyroligneous acid". There are no standards of identity, prescribed production methods, or tests which distinguish between liquid smoke and pyroligneous acid; they can be considered to be the same. However, the numerous variables that are manipulated during pyrolysis do lead to a wide range of compositions of the condensates. In addition, implementation of many further processing steps by concentration, dilution, distillation, extraction, and use of
food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used f ...
s has led to the many hundreds of different products on the market worldwide. Wood, particularly hardwood, is by far the most widely used biomass pyrolyzed to make liquid smoke. Commercial products are made using both batch and continuous methods. Commercial products are made using a range of reactors from rotary calciners, heated screws, batch charcoal kilns, to fast pyrolysis reactors. The process type and conditions of processing lead to greater variances between the condensates than the differences between the common wood types that are in use. Variables such as feed rate, vapor residence time, particle size, oxygen infiltration, and temperature can have substantial effects on yield and composition of the condensates. Wide ranges of chemical composition are reported throughout the literature and unless the process and conditions are cited, there is limited utility of such results. Commercial manufacturers strive to control their manufacturing variables in order to standardize product compositions. Water is added either during condensation or after to cause separation of three fractions. Once water is added, the aqueous phase becomes the largest and most useful fraction. It contains wood-derived
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
s of higher
chemical polarity In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. Polar molecules must contain one or more polar ...
such as those found in
carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
,
aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...
, and
phenol Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire. The molecule consists of a phenyl group () ...
chemical classes. Many compounds together are responsible for the flavor, browning, antioxidant, and antimicrobial effects of smoke and liquid smoke. The smallest condensed fraction is the lowest-polarity upper phase which a mix of
phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified ...
s and other oily, waxy substances. The lower phase is commonly referred to as tar. It is an intermediate-polarity mixture of phenolic polymers, secondary and tertiary reaction products, some of the water-soluble polar compounds partitioned in the amount of which is governed by individual
partition coefficient In the physical sciences, a partition coefficient (''P'') or distribution coefficient (''D'') is the ratio of concentrations of a chemical compound, compound in a mixture of two immiscible solvents at partition equilibrium, equilibrium. This rati ...
s, water and the bulk of the
polycyclic aromatic hydrocarbon A Polycyclic aromatic hydrocarbon (PAH) is any member of a class of organic compounds that is composed of multiple fused aromatic rings. Most are produced by the incomplete combustion of organic matter— by engine exhaust fumes, tobacco, incine ...
s. Wood tar has been used as a preservative, water repellent, and antiseptic. Tar from birch was produced as a commodity product on large scale in northern Europe. Today commercial liquid smoke products are still prepared from this phase. Liquid smoke condensates are made commercially for the global
meat industry The meat industry are the people and companies engaged in modern industrialized livestock agriculture for the production, packing, preservation and marketing of meat (in contrast to dairy products, wool, etc.). In economics, the meat industry is ...
in the U.S. and Europe and are regulated by governments. Liquid smoke is still referred to as wood vinegar, and is made and used indigenously in places including Japan, China, Indonesia, Malaysia, Brazil, and Southeast Asia.


Use


Food

The application of liquid smoke to food has grown to encompass a wide variety of methods employing thousands of commercial formulations worldwide. Liquid smoke is used extensively by topical application to replace direct wood-smoking of food. In addition to flavor, reaction color, anti-microbial, and texture effects are obtained by topical addition followed by thermal processing. Dipping products in diluted solutions or soaking them in brines containing liquid smoke followed by heating was done long before the modern industrial era using Wright's liquid smoke and pyroligneous acid precursors. Allen patented a method of regenerating smoke using air atomization, which is still the leading technology for using condensed smoke products to treat processed meat, cheese, fish, and other foods in batch smokehouses. As the meat-processing industry has consolidated, continuous processes have evolved, and direct applications of solutions of liquid smoke via showering or drenching systems installed on continuous lines are the usual methods of application. In North America, there are more than thirty-five processed-meat plants utilizing bulk tanks to receive tankers of liquid smoke for topical application as an alternative to direct wood smoking. Topical application by impregnation of fibrous, laminated, and plastic casings is also used; meat products are stuffed into these casings and thermally processed. The use of natural condensed smoke preparations internally in food is another way to impart smoke flavor, used when other technical functions of smoke do not need to be expressed in a finished food. This can be done directly by adding into blenders with meat or other foods, or injecting whole muscle meat. The smoke flavors can also be incorporated into sauces such as barbeque or dry seasonings. Aqueous smoke solutions can also be extracted into oil, spray-dried using maltodextrin carriers, or plated onto foods and food ingredients such as malt flour, yeast, or salt.


Non-food

Extensive references to beneficial uses of pyroligneous acid in plants for seed germination, pest control, microbial control, plant structural enhancements are reported. Livestock benefits such as antimicrobial preservation of feed, nutrient digestibility, and other claims are found. Scientific agricultural studies can be found in peer-reviewed journals, but many agricultural benefits such as
soil quality Soil quality refers to the condition of soil based on its capacity to perform ecosystem services that meet the needs of human and non-human life.Tóth, G., Stolbovoy, V. and Montanarella, 2007. Soil Quality and Sustainability Evaluation - An integ ...
improvement, better seed germination, and healthier foliage are widely promoted without attribution. Broad claims of medical benefits to humans in digestive ailments, dental infections, liver, heart, skin ailments, ears, eyes are found, but the literature is devoid of accepted scientific studies for such testimonial claims in humans.


Safety

The first government-sanctioned assessment of liquid smoke was undertaken by the United States
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA) in 1981. The committee commissioned by the FDA to evaluate information on the products concluded there was no evidence demonstrating the products were a hazard to the public the way they were being used. Today, these products stand as
Generally Recognized as Safe Generally recognized as safe (GRAS) is a United States Food and Drug Administration (FDA) designation that a chemical or substance added to food is considered safe by experts under the conditions of its intended use. An ingredient with a GRAS d ...
(GRAS) in the United States and may be used at levels necessary to produce the intended technical effects. Manufacturing plants where liquid smoke is made are regulated and inspected by the FDA. The
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
established procedures for the safety assessment and the authorization of smoke flavorings used or intended for use in or on foods in 2003. The
European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002 ...
(EFSA) was charged with evaluating information on primary condensate smoke flavorings. Information on twelve products from ten applicants were evaluated by EFSA. Opinions were published on all twelve. The products considered were what each applicant considered their own primary product prior to any further processing or derivatization. All twelve products were determined to be genotoxic positive by
in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...
methods. However, when evaluated by
in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, an ...
methods ten were found to not be of concern by EFSA. The AM-01 product was judged inconclusive and FF-B was considered weakly genotoxic. Based upon the NOAEL determinations for each product and supplemental information supplied by some manufacturers, usage limits for most products have been established and are conveyed by manufacturers to users. Most of these primary products and their derivatives remain in commercial use. Only products which are the subjects of these evaluations are authorized to be used in commerce within the EU.


References


External links


Leffingwell & Associates, Smoke Flavor I.
Includes chemical and chromatography information. {{DEFAULTSORT:Liquid Smoke Food additives Smoked food Wood products