Smoke and liquid smoke. Study of an aqueous smoke flavouring from the aromatic plant Thymus vulgaris L

An aqueous smoke flavouring from Thymus vulgaris L was obtained. The qualitative and quantitative composition of its dichloromethane extract was studied by gas chromatography and gas chromatography/mass spectrometry. In addition to the common smoke components such as aldehydes, ketones, diketones, esters, acids, furan and pyran derivatives, alkyl aryl ethers, phenol, guaiacol and syringol derivatives, some terpenic compounds were detected. Differences between this aqueous liquid smoke and others from various kinds of wood are due not only to the absence or presence of some compounds but also to the proportions of the different groups of components present in the mixture. Some aldehydes, esters, guaiacol and its derivatives and terpenic compounds contribute to the overall odour of this liquid smoke more significantly than the ketones, furan and pyran derivatives, acids, phenol and its derivatives and syringol. The yield in smoke components obtained from the pyrolysis of Thymus vulgaris L at 488 °C is of a similar order to that obtained from other woods. © 1999 Society of Chemical Industry     

Textural and physicochemical changes in salmon (Salmo salar) treated with commercial liquid smoke flavourings

The textural and physicochemical properties of fillets of farmed Atlantic salmon (Salmo salar) treated with two commercial liquid smoke flavourings (LS1 and LS2) were examined after 15, 30 and 45 days of storage at 2 °C in oxygen impermeable bags. Salmon flesh treated with LS1 was characterized by high water-soluble protein, fat and moisture contents, plus low hardness, fracturability, gumminess and chewiness, and a low alkali-insoluble protein content. These characteristics were similar to those of control salmon (not treated with liquid smoke flavouring). Storage time changed these properties similarly in both. Salmon flesh treated with LS2 was characterized by high hardness, fracturability, gumminess, chewiness and alkali-insoluble protein levels, plus low water-soluble protein, fat and moisture contents. Storage time appeared to have a far less important effect on salmon flesh treated with LS2.     

Functionality of liquid smoke as an all-natural antimicrobial in food preservation

The smoking of foods, especially meats, has been used as a preservation technique for centuries. Today, smoking methods often involve the use of wood smoke condensates, commonly known as liquid smoke. Liquid smoke is produced by condensing wood smoke created by the pyrolysis of sawdust or wood chips followed by removal of the carcinogenic polyaromatic hydrocarbons. The main products of wood pyrolysis are phenols, carbonyls and organic acids which are responsible for the flavor, color and antimicrobial properties of liquid smoke. Several common food-borne pathogens such as Listeria monocytogenes, Salmonella, pathogenic Escherichia coli and Staphylococcus have shown sensitivity to liquid smoke in vitro and in food systems. Therefore liquid smoke has potential for use as an all-natural antimicrobial in commercial applications where smoke flavor is desired. This review will cover the application and effectiveness of liquid smoke and fractions of liquid smoke as an all-natural food preservative. This review will be valuable for the industrial and research communities in the food science and technology areas.     

巴氏消毒乳储存过程中化学与微生物变化

通过研究不同储存温度的巴氏消毒乳感官品质、生化指标和微生物数量,来确定影响巴氏消毒乳品质的主要因素。结果表明,在5 d的储存期内,巴氏消毒乳在4℃和8℃储存条件下感官品质变化趋势几乎一样,在12℃储存条件下感官品质下降趋势较4℃和8℃储存条件下快。巴氏消毒乳中脂肪酶的活力、TBARS值和蛋白水解程度均随着储存时间的延长而逐渐升高,SDS-PAGE显示主要蛋白未见明显分解,金黄色葡萄球菌未检出,嗜冷菌的数量逐渐减少,菌落总数呈现对数生长趋势并在储存的第4天达到稳定期。巴氏消毒乳中残存的脂肪酶、蛋白酶和微生物是影响巴氏消毒乳品质的主要因素。     

Spray application of liquid smoke to reduce or eliminate Listeria monocytogenes surface inoculated on frankfurters

In a simulated post process contamination scenario liquid smoke was sprayed on the frankfurters after peeling, and then inoculated with Listeria monocytogenes (Lm). Samples that did not receive a liquid smoke spray remained at approximately 2 log cfu/cm² during the 48 h of storage while the levels on the liquid smoke treated frankfurters continued to decline until they were below detection level (1 cfu/100 cm²). A shelf-life study lasting 140 days indicated that liquid smoke suppressed the growth of Lm for up to 130 days. An application of 2 or 3 ml liquid smoke at packaging resulted in at least a 1 log reduction of Lm within 12 h post packaging.     

Effect of storage environment on carrot root rots and biochemical changes during storage

 The optimum temperature and relative humidity for the development of carrot root rot during storage were found to be 20°C and 60%, respectively, and rot development increased as these environmental factors increased in magnitude. Temperature and relative humidity both enhance the biodeterioration of the carrot root through an increase in the diameter the rotted area of infected roots. The rot during storage was found to be caused by Rhizopus oryzae, Trichoderma harzianum, Botryodiplodia theobromae, Aspergillus niger and Aspergillus flavus. The fungi enter through wounds and natural openings. The amounts of total soluble sugar in rotted carrot root were substantially decreased 2 – 4 days after infection and paper chromatography showed the presence of glucose, maltose, sucrose, lactose and galactose in healthy carrot roots, while only lactose and galactose were present in infected roots. The ascorbic acid, total nitrogen, crude protein, crude fibre, fat and mineral contens in infected carrot roots reduced as the storage period was prolonged. Received: 16 October 1996     

Modeling changes in rheological properties of potatoes during storage under constant and variable conditions

The changes in rheological properties of potatoes stored at 5, 15, 25 °C and variable (fluctuating) temperature for 16 or 26 weeks were evaluated in terms of elasticity and viscosity parameters using axial compression and creep tests. Cylindrical test specimens (15 mm diameter and 30 mm long) were used. A third-degree polynomial best fitted the force-deformation curves in axial compression test (R²=0.98-0.99) whereas a four-element (Burgers) mechanical model adequately described the creep response of potatoes (R²=0.95-0.99). The tangent modulus of elasticity in axial compression and elasticity and viscosity parameters in creep tests in general decreased significantly (P<0.05) with increase in storage time both under constant and variable storage conditions. The changes in rheological properties of potatoes stored under constant storage condition were sufficiently described by a modified exponential model (R²=0.89-0.96) except for the viscosity parameter of the Maxwell component of the four-element model. The logarithm of degradation rate constant, k, and the constant, n, were linearly related to storage temperature. For the variable storage condition, a bulk mean temperature (T_bm) was calculated to account for a series combination of storage time and temperature to which the potatoes were subjected. The changes in rheological properties due to variable storage temperature were then described as a function of T_bm and storage time, t_s, using stepwise multiple regression. The result indicated that except the viscosity parameter of the Maxwell component of the four-element model, it was possible to describe the changes in rheological properties as a function of T_bm and t_s (R²=0.84-0.99).     

Quality changes of burnt aromatic coconut during 28-day storage in different packages

The shelf-life of unwrapped, film-wrapped and vacuum-packed burnt aromatic coconut was studied at 5±1 °C and 80-90% relative humidity. Regardless of the packaging treatments, weight loss of whole burnt coconut increased with storage time. Transmittance and lightness (L*) values of coconut water decreased (P<0.05) with longer storage time. The pH of coconut water and coconut meat from the vacuum-packed treatment decreased as storage time increased. Sensory analysis showed that, for all treatments, the yellowness intensity of coconut water increased whereas its transparency decreased with time. The sourness intensity of vacuum-packed coconut water increased on later days of storage. Only the film-wrapped coconut, having the shortest shelf-life, had mold on its shell and husk at the end of storage. This study showed that the unwrapped, film-wrapped and vacuum-packed burnt coconuts could be stored for up to 14, 18 and 28 days, respectively, under the conditions used in this study.     

Evaluation of changes during storage of probiotic dahi at 7°C

Low-fat probiotic dahi (an Indian traditional fermented milk product like yogurt) prepared with lactococci starter and two adjunct probiotic cultures of Lactobacillus acidophilus and Lactobacillus casei was stored at 7°C. The survival of bacterial species was affected during storage of dahi, in which viable counts increased up to 2 days and gradually decreased from 2 days, up to 8 days. The quality of refrigerated dahi was assessed by a panel of trained judges. On storage, pH significantly decreased over storage time, indicating that the dahi samples did not develop much acidity under the storage conditions of the study. However, after 8 days of storage, the samples were disliked by the panel, which reported slight bitterness, which may have been due to proteolysis. Proteolysis increased during storage. More α_s1-casein was degraded than β-casein. On the basis of the results of this study we can conclude that dahi stored up to 8 days may be acceptable to consumers.     

Identification of phenolics in Chinese toon and analysis of their content changes during storage

The tender leaves and sprouts of Chinese toon are considered to be a popular vegetable with a unique flavour. The phenolics of Chinese toon were separated and identified by HPLC–MS/MS. Gallic acid, its derivatives and quercetin-3-O-rhamnoside, were found to be the main phenolics in Chinese toon. The changes of the phenolics in Chinese toon during storage at 0, 5, 10 and 20 °C were also studied by HPLC. Results showed that, during storage, the contents of phenolics in Chinese toon first increased and then decreased as storage was prolonged.     

Factors affecting elimination of polycyclic aromatic hydrocarbons from smoked meat foods and liquid smoke flavorings

This review deals with effects of environmental and physicochemical factors affecting polyaromatic hydrocarbon (PAH) elimination from smoked meat products and liquid smoke flavoring (LSF). In the introductory part, some essential information are aimed at principles of food smoking and PAH formation during smoke generation as a result of incomplete wood combustion. Also, an application of alternative technology for food aromatization using LSF is briefly mentioned. Similarly, latest European legislation, biological effects, and analytical aspects of PAHs are mentioned concisely. The main part is devoted to physicochemical factors affecting the PAH content in smoked meat products, such as light, additional cooking, and packaging, which are able to decrease considerably PAH content in some meat products. The most important effect on PAH concentration decrease in LSF has low-density polyethylene (LDPE) package due to sorption processes on a surface of the plastic with subsequent diffusion into the plastic bulk. A less effective material is polyethylene terephthalate (PET), when only a surface adsorption process comes into account. Moreover, this process is affected also by other compounds presented in liquid media able to compete for the adsorption center on the PET surface.     

Stability of carotenoids in tomato juice during storage

The stability of carotenoids in tomato juice during storage was studied. Tomato juice was processed by hot-breaking of tomatoes at 82 °C, screening, heating at 121 °C for 40 s and then storing in the dark or under light at 4, 25 and 35 °C for 12 weeks. Results showed that the amounts of all-trans-lutein and its cis isomers decreased with increasing storage time for all the treatments. Light enhanced the degradation and isomerization of all-trans-lutein, and 13-cis-lutein was more susceptible to formation than 9-cis-lutein. Similar trends were observed for β-carotene and lycopene. However, light exposure promoted the formation of di-cis-, 9-cis- and 13-cis-β-carotene. For lycopene, 15-cis-lycopene was the major isomer formed during dark storage at 4 °C, while 9-cis- and 13-cis-lycopene were favoured at 25 °C and 5-cis- as well as 13-cis-lycopene dominated at 35 °C. Under light storage, both 9-cis- and di-cis-lycopene (II) were the main isomers generated at 35 °C, whereas 13-cis- and 15-cis-lycopene were the most abundant at 4 and 25 °C.     

Changes in unreacted starch content in corn during storage

In the dry grind process, corn is ground, mixed with process water and cooked; starch is enzymatically hydrolyzed to sugars, and subsequently fermented to ethanol by yeast. The conversion of starch into ethanol, however, is not complete as distillers dried grains with solubles (DDGS) often contain more than 5% starch. The amount of unreacted starch represents inefficiencies in the process and reducing this amount is important to improving profitability of the ethanol industry. Additionally, dry grind facilities have reported seasonal variation in ethanol yields. In order to minimize variation in ethanol yields and the amount of unreacted starch in DDGS, it is important to understand the effects that storage temperature and time have on the digestibility of the corn starch. While starch quality is largely controlled by genetics and growing conditions, postharvest practices (handling, storage, and processing conditions) also affect starch composition and structure. In this study, changes in unreacted starch content of corn during storage were monitored to provide an explanation for the seasonal variation in ethanol yields observed by dry grind facilities. Yellow dent corn was harvested in 2011 and 2012 and stored indoors, outdoors, and under refrigeration for 5–12 mo. Results with the 2011 harvest corn showed unreacted starch content ranging from 2.17 to 14.1% over a 48 wk period. Unreacted starch was more influenced by storage time, initially decreasing at a rate of 0.31% per wk during the first 10 wk and steadily increased at an average rate of 0.16% per wk for the duration of storage. Results with the 2012 harvest corn, however, showed a higher average unreacted starch content of 13.0% during 20 wk of storage and no appreciable change in unreacted starch content regardless of storage temperature.     

Biochemical changes in an intermediate moisture cecina-like meat during storage

Biochemical and microbiological changes in two cecina-like products were evaluated during storage. Two products were prepared, one by salting and the other by infusion in a salt-glycerol solution. The samples were vacuum packed and tested monthly for pH, colour, haematin complex, soluble nitrogen and microbiological spoilage. Proteolysis and increase in pH showed a high correlation for both samples. Temperature-dependent changes in colour and concentration of haematin complex during storage were also found in both samples. The activation energy for haematin transformation was found to be around 1 kcal/mol. Based on the low activation energy for haematin complex degradation (around 1 kcal/mol) for both samples, this process may be regarded as a low energy biochemical process.     

Nutritional characterization and changes in quality of Salicornia bigelovii Torr. during storage

Salicornia bigelovii Torr. (sea-beans or drift seeds in English, sea-asparagus in Chinese) is an oil-seed plant tolerant to seawater irrigation and perishable with a shelf life of only about 6 days at ambient temperature (25 °C). To provide a potential food supplement, nutritional value of S. bigelovii were determined together with its postharvest quality as affected by storage temperatures (0 °C, 2 °C, 8 °C and 25 °C). Nutritional analyses showed that S. bigelovii contained high vitamins and minerals, which made it an ideal nutritional and diet supplement. Storing S. bigelovii at low temperatures could be a practical technique to extend storage life by reducing the quality degradation. After conducing sensory evaluations and determining ascorbic acid and chlorophyll contents, the optimal temperature for storing S. bigelovii was around 2 °C. This research will help to develop technically effective and energy efficient methods for prolonging the shelf life of S. bigelovii.     

Character impact odorants of boiled chicken: changes during refrigerated storage and reheating

 The most potent odorants of freshly boiled chicken and boiled, refrigerated and reheated chicken showing warmed-over flavour (WOF) were screened by dilution experiments. In total, 20 odorants were selected for quantification by stable isotope dilution assays. Calculation of odour activity values (ratio of concentration to odour threshold) indicated methanethiol, (E,E)- and (E,Z)-2,4-decadienal, (E,E)-2,4-nondienal, 2-furfurylthiol, hexanal, octanal and acetaldehyde as the character impact odorants of freshly boiled chicken. Refrigerated storage and reheating of boiled chicken led to a loss of meaty, chicken-like and sweet odour notes and to the formation of green, cardboard-like, metallic off-odours. These changes were mainly caused by a sevenfold increase of hexanal and a sixfold decrease of both (E,E)-2,4-decadienal and 2-furfurylthiol. Sensory experiments confirmed this conclusion. Received: 11 February 1997     

Character impact odorants of boiled chicken: changes during refrigerated storage and reheating

 The most potent odorants of freshly boiled chicken and boiled, refrigerated and reheated chicken showing warmed-over flavour (WOF) were screened by dilution experiments. In total, 20 odorants were selected for quantification by stable isotope dilution assays. Calculation of odour activity values (ratio of concentration to odour threshold) indicated methanethiol, (E,E)- and (E,Z)-2,4-decadienal, (E,E)-2,4-nondienal, 2-furfurylthiol, hexanal, octanal and acetaldehyde as the character impact odorants of freshly boiled chicken. Refrigerated storage and reheating of boiled chicken led to a loss of meaty, chicken-like and sweet odour notes and to the formation of green, cardboard-like, metallic off-odours. These changes were mainly caused by a sevenfold increase of hexanal and a sixfold decrease of both (E,E)-2,4-decadienal and 2-furfurylthiol. Sensory experiments confirmed this conclusion. Received: 11 February 1997     

Effects of catching methods on quality changes during storage of cod (Gadus morhua)

The catching method, storage time and composition of fish are factors that influence the quality of fish. Different opinions have been expressed concerning the effect of catching methods on the fish quality. In this work cod caught at the same time and location, using different catching methods (gillnet and longline) has been stored for up to 16 days. The same soaking time was used for both fishing gears. No differences due to fishing gear was observed in the quality attributes QIM score, water content, TVN, DMA, TMA, TMAO, Freshmeter-readings, total viable count, sulphide producing bacteria and P. phosphoreum during storage. The catching method had significant influence on pH only. It is shown that the pH of the fish caught by gillnet is lower than pH of fish caught by longline. It is also shown that fish caught by gillnet have higher K-factor than fish caught by longline. The pH of the fish muscle is closely correlated to K-factor; higher K-factor supports lower pH.It is also shown that by using the quality parameters water content, TVN, DMA, QIM score, Freshmeter-readings, TVC, sulphide producing bacteria, and P. phosphoreum, the storage time in ice can be predicted with a correlation of 0.99 and a prediction error of 0.8 day.     

Sensory changes in liquid milk during storage and the effect on consumer acceptance

The acceptance of dairy products by consumers is generally determined by the product's sensory characteristics. These characteristics are a result of various changes in the product and the surrounding environment. The purpose of this paper is to report on a detailed sensory and consumer investigation of the changes in liquid skimmed milk held over an eight day period at three different storage temperatures: 1°C, 5°C and 10°C. Results of an objective sensory profile and subsequent data analysis revealed that sensory changes in milk could be described and quantified, clearly indicating the product's shelf-life profile. Product acceptability as perceived by consumers was undertaken on a subset of samples, illustrating the points at which consumers noticed significant changes. Overall, as the samples went through their shelf-life at the higher temperature they became less acceptable. The final part of the experiment used statistical modelling procedures to interpret and understand the data. As expected, it was shown that products became more stale during storage, and that temperature of storage affected the rate of staling, this being most marked at the higher temperature. Staleness was related to the attributes vegetable, sour, cardboard, chalky and mouthcoating.