Trim size: 216mm x 279mm Toldra c06.tex V1 - 07/03/2014 11:36 A.M. Page 39 6 Principles of Smoking Zdzisław E Sikorski and Izabela Sinkiewicz Department of Food Chemistry, Technology, and Biotechnology, Gdansk´ University of Technology, Gdansk,´ Poland 6.1 Introduction condensate and so move the in form of tiny solid particles or liquid droplets to the dispersed phase. The phenolic fraction, about 240 items, contains mainly guaiacol Treatment of a large variety of foods with wood smoke has been and its derivatives, phenol, 2,5-dimethylphenol, cresols, syringol and practiced for centuries—predominantly meats, poultry, and fish, but itsderivatives,pyrocatechins,resorcinol,pyrogallol,hydroquinone, also scallops, cheeses, prunes, paprika, and the malt used to produce and hydroxy-dimetoxyphenylo-ketones. The composition of the whiskey and some sorts of beer. The process usually includes salting phenolic fraction depends on the temperature of smoke generation. and partial drying; it may also be coupled with heating. The aim is Increasing the temperature decreases the content of syringol and to increase the shelf life of the products, prevent food poisoning, 4-methylguaiacol and the percentage of trans-isoeugenol. The and add a desirable smoky flavor. Smoking is applied at both an highest yield of smoke phenols occurs in the temperature range industrial scale in food processing plants and at the small scale of 480–520 ∘C. The smoke aldehydes and ketones are also numerous. traditional home cooking. With the advent of canning, freezing, Formaldehyde is generated by the oxidation of methanol, one of and the refrigeration chain, the preservative effect of smoking has themainproductsofthedrydistillationofwood.Thegroupof gradually lost its importance. The process parameters required to carbonyl compounds includes inter alia acetaldehyde, benzalde- obtain a very long shelf life through smoking are very severe and hyde, acetone, and furanone. The acid fraction contains mainly may decrease the nutritional value of a product and increase the acetic acid, other components being various short-chain carboxylic health risks for the consumer. and ketocarboxylic acids. Among the alcohols are a variety of low-molecular-weight aliphatic compounds. Several components have been identified also in the ester fraction. 6.2 Wood-smoke composition The group of hydrocarbons comprises various aliphatic compounds and polycyclic aromatic hydrocarbons (PAHs). Wood Smoke develops from the charring of wood: beech, oak, alder, hick- smoke contains about 60 identified PAHs, differing in number ory, or maple, as well as fruit trees. Pinewood is used only seldom. To of aromatic rings and structure, as well as in physical and bio- produce the desirable flavor that is characteristic of some products, logical properties. Among them are the following 16 potentially juniper berries or pinecones are added to the smoldering material. mutagenic and/or carcinogenic ones: cyclopenta[cd]pyrene, The wood usually takes the form of shavings or sawdust. Today, these benzo[a]nthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluor- are available commercially in different assortments of standardized anthene, benzo[k]fluoranthene, benzo[a]pyrene (BaP), benzo[ghi] mesh size and moistness. In old-type kilns and friction-type genera- perylene, dibenzo[ah]anthracene, dibenzo[ae]pyrene, dibenzo[ah] tors,woodlogsarealsoused. pyrene, dibenzo[ai]pyrene, dibenzo[al]pyrene, indeno[1,2,3-cd] The thermal decomposition of the woody material, followed by pyrene, 5-methylchrysene, and benzo[c]fluorene. The structure oxidation, generates hundreds of solid, liquid, and gaseous com- of these compounds determines their biological activity, because pounds, differing in boiling point, solubility, chemical properties, in the living organism they are activated on different routes, and the role they play in food smoking. These are mainly H2O, which are catalyzed by various enzymes. The concentration of CO, CO2, alcohols, carbonyl compounds, carboxylic acids, esters, PAH in wood smoke depends mainly on the temperature of hydrocarbons, nitrogen oxides, and phenols. The yield of the various the smoldering wood and on the access of air. Increasing the componentsdependsonthespeciesofwoodandthesmoldering smoke-generation temperature leads to a larger proportion of the parameters. Mixed with air, they form a complex aerosol. The mass high-molecular-weight compounds in the total PAH. The content proportion of the dispersing and dispersed phases of the aerosol of PAHs in the smoke can be minimized by keeping the glowing dependsonthechemicalcompositionoftheconstituentsandon temperature below 400 ∘Candremovingthetar. temperature: heating increases the concentration of components Wood smoke can be condensed and purified, yielding various in the gaseous phase, while cooling causes many compounds to preparations. These are used for smokeless smoking of meats. HandbookofFermentedMeatandPoultry, Second Edition. Edited by Fidel Toldrá. © 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd. 39 Trim size: 216mm x 279mm Toldra c06.tex V1 - 07/03/2014 11:36 A.M. Page 40 40 Handbook of Fermented Meat and Poultry TheconcentrationofPAHsinsuchpreparationscanbeeffectively from 30 to 72 μg/g of the sum of guaiacol, 4-methylguaiacol, controlled. According to EU Directive 2065/2003, the BaP content in syringol,eugenol,andtrans-isoeugenol (Hitzel et al., 2012), while smoke preparations must not exceed 10 ng/g (European Parliament, hot-smoked frankfurter-type sausages contain 19.6–57.6 μg/g, 2003). depending on the process parameters (Pohlmann˝ et al., 2012). Compounds with an additional aldehyde group in their structure are more effective antimicrobials than phenols. The sensitivity of 6.3 The preserving effect different species and strains of microorganism towards various phenolsmaysignificantlydifferinbrothandinsmokedmeat Smoking of foods can be regarded as “hurdle technology” products. The growth inhibitory concentration of some smoke (Figure 6.1). Smoked products are not sterile. The preserving effect phenols in broth towards Listeria monocytogenes is in the range of results from the consecutive or simultaneous action of several of the 10–100 μg/g.However,asyetitisnotpossibletopredictexactly following factors: thermal inactivation of the product’s microflora, the concentration of total smoke phenols that is necessary for an water activity, pH, antibacterial activity of additives used prior to inhibitory effect on, for example, L. monocytogenes or Clostridium smoking, concentration of antimicrobial and antioxidant smoke botulinum in foods. Cold smoking may decrease the population of components in the product, barrier properties of the packing, L. monocytogenes on the surface of the products, but might also lead and storage temperature. Therefore, the high-quality life and the to proliferation of these bacteria in meats cured with contaminated practical storage time of various smoked foods extends from a brine. The growth of L. monocytogenes has been shown in various few days in refrigeration conditions to several months at room ready-to-eat smoked products. temperature, depending on the kind, initial freshness, microbial Smoke carbonyl compounds, especially formaldehyde, are also contamination, and form of the raw material, on the parameters known to retard the proliferation of microorganisms. Smoked meats of salting and curing, on loss of water due to dripping or drying, may contain up to 125 μg/g formaldehyde. Most sensitive are the temperature, duration, and smoke density in the smokehouse, and vegetative forms of bacteria; molds and yeasts are more resistant. on the conditions of packaging and storage of the product. Manymoldswereisolatedfromfullyripened,lightlysmoked Numerous components of wood smoke have antimicrobial Norwegian dry-cured meats, and the predominant species were activity in concentrations similar to those found in smoked meats. foundtobelongtothegenusPenicillium (Asefa et al., 2009). Among the most active are various phenols, especially guaiacol and Generally, smoke components alone cannot protect lightly its derivatives, cresol, pyrocatechols, and pyrogallol. The contents smoked foods from spoilage and microbial hazards for long. At and distributions of the phenols and their derivatives in smoked the concentrations found in foods, the smoke constituents do not meats are related to their solubility in the lipid and water phases of decrease the population of various pathogenic microorganisms by the products, as well as to the smoking conditions. Mini-salamis several log cycles, or efficiently restrain their growth. A significant in sheep casings, 18–20 mm in diameter, smoked for 30 minutes antilisterial effect can be achieved by adding potassium lactate and at 22 ∘C with smoldering smoke from beechwood chips, contain sodium diacetate to the sausage formulation and by 2 minutes’ 1 2 3 4 5 6 7 8 9 Log number of bacteria / g 10 11 Downloaded from mostwiedzy.pl Time of storage Figure 6.1 Effect of preservative treatments on the growth of bacteria in foods: (1) untreated food, room temperature; (2) refrigeration; (3) chemical preser- vation and refrigeration; (4) chemical preservation, modified atmosphere, and refrigeration; (5) drying or salting, room temperature; (6) marination or lactic acid fermentation, room temperature; (7) drying or salting and refrigeration; (8) freezing; (9) heat pasteurization, room temperature; (10) heat pasteurization and chemical preservation, room temperature; (11)