Note Changes in the Physicochemical and Volatile Flavor Characteristics of Scomberomorus Niphonius During Chilled and Frozen
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Food Sci. Technol. Res., 18 (5), 747–754, 2012 Note Changes in the Physicochemical and Volatile Flavor Characteristics of Scomberomorus niphonius during Chilled and Frozen Storage * Bin ZHANG, Shang-Gui DENG and Hui-Min LIN Department of Aquatic Product Processing and Storage, College of Food and Pharmacy, Zhejiang Ocean University, Zhoushan 316000, China Received April 8, 2012; Accepted June 1, 2012 Changes in chemical, textural, and volatile flavor properties were investigated for mackerel fish (Scomberomorus niphonius) stored in cold rooms (5℃ and 0℃) and freezers (−20℃ and −55℃). Corre- lation and multivariate analysis showed a significant time-dependent relationship between total volatile base nitrogen (TVBN)/ trimethylamine (TMA) (Y) and storage time (X) for fish stored in cold rooms, with R = 0.996 − 0.997 values of Gompertz model (Y = a*exp(−exp(b − cX)), and there was a good linear rela- tionship between TVBN and TMA. Combined with the textural properties, the polynomial fitting model (Y = a + bX + cX2 +…, R = 0.982 − 0.991) was applied and elucidated the correlation between the hard- ness/springiness (Y) and TVBN (X), the rational function model (Y = (a + bX)/(1 + cX + dX2), R = 0.975 − 0.979) used for the chewiness (Y) and TVBN (X). The electronic nose analysis revealed that the variation of muscle volatile flavor compounds was found out along the PC1 to the right, and then along the PC2 to the upward and further to the downward based on the principal component analysis (PCA). Further- more, the linear discriminant analysis (LDA) had better distinction effect for the changes of fish flavor than PCA. Results from this study suggested that the texture analysis in combination with electronic nose techniques might be utilized as a rapid expeditious process for predicting quality and shelf life of the fresh fish or other aquatic products. Keywords: Scomberomorus niphonius, TVBN, TMA, texture properties, electronic nose Introduction specific spoilage organisms from various sources (Tzikas et The pelagic mackerel fishes are important fishery re- al., 2007; Shi et al., 2008). sources which are wildly distributed in all temperate and Freshness is the most common and fundamental criterion tropical seas, such as the East China Sea, Pacific coast of for the quality and acceptability of fish or fishery products. Japan, and regions of Indian and Russia (Bae et al., 2011). Microbiological, biochemical, and sensory analysis have The fish constitutes desirable components of a healthy diet, been used to evaluate the freshness and quality of fish during including polyunsaturated fatty acids, essential amino acids, handling and storage (Ozogul et al., 2011). The biochemical vitamins, and minerals. However, this species is highly per- properties, such as total volatile base nitrogen (TVBN) and ishable during processing and storage, due to large amounts trimethylamine (TMA), have been frequently used as the in- of non-protein nitrogen, high content of fat and autolytic dicators for the quality of fish, due to the correlation between enzymes in tissues, which deteriorates rapidly post-mortem organoleptic characteristics and microbial spoilage. How- resulting in formation of an obvious off-taste and soften tex- ever, with respect to the degree of spoilage or microbial me- ture (Simeonidou et al., 1998). What’s more, these problems tabolites, the biochemical analyses are tedious or time-con- will be accelerated by storage conditions such as abominable suming and may encounter serious safety concerns through temperature and moisture in environment and overgrowth of the contact of chemical reagents, such as toluene and trichlo- roacetic acid used in TVBN and TMA determination (Malle *To whom correspondence should be addressed. et al., 1987). The sensory evaluation is the most popular way E-mail: [email protected] of assessing quality of fish, which provides the fast, simple 748 B. ZHANG et al. and visible quality information for the consumers (Goulas et homogenate filtrate was measured using a digital pH-meter al., 2007), but it is often subjective and inaccurate, therefore, (PHS-25, Shanghai Precision & Scientific Instrument Co. requires trained panels to perform analysis. In addition, the Ltd., Shanghai, China). sensory evaluations also may introduce serious safety risk Biochemical analysis The total volatile base nitrogen factors as those of toxin production (such as biogenic amines (TVBN) was determined by steam-distillation of trichloro- in mackerel fish). Texture of raw fish can be measured by acetic acid (TCA)-fish extract, using the modified method of different methods (puncture, compression, shear and tensile Malle et al. (1987). The fish muscle (10.0 g) was added to stress). Among them, the shearing force and compression 100 mL of 0.60 mol/L TCA solution and homogenized at a methods are recommended for use with fresh fish (Martinez speed of 10,000 rpm for 2.0 min (0 − 4℃). The homogenate et al., 2007). Some of the information is available about the was centrifuged at 5000 g for 5 min (LD5-2A Centrifuge, texture assessment of mackerel fish, but little is known about Beijing Lab Centrifuge Co., Ltd., Beijing, China). Five mil- the correlation among the textural characteristics, spoilage liliters of supernatant were transferred to a Kjeldahl-type dis- degree and storage behavior (Mishima et al., 2005). tillation tube followed by additions of 5.0 mL of 0.80 mol/L It is necessary to use the chemical and physical methods NaOH solution, a drop of phenolphthalein indicator and two when the purpose is to adequately define and assess the fish drops of silicon oil. Steam-distillation was pipetted into the quality, and ensure that those results show good agreement inner ring for 6.0 − 7.0 min. The distillate was collected in a with the objective tests. Thus, the objectives of this study flask containing 10.0 mL of 0.50 mol/L boric acid solution. were to investigate changes in the quality of mackerel fish Finally, the boric acid distillate was titrated with 0.01 mol/L during storage at different temperatures over time based on HCl solution until the color turned to bluish violet. biochemical analysis and establish a model for rapid assess- The trimethylamine (TMA) was determined according to ment of quality and shelf life using textural and volatile fla- the procedure of AOAC with minor modifications (AOAC vor characteristics obtained from this study. 1972). Ten grams of fish muscle were blended with 70 mL of distilled water and then homogenized at a speed of 10,000 Materials and Methods rpm for 1.0 min. The homogenate was mixed with 10.0 mL Samples preparation and storage Fresh mackerel of 40% (w/v) TCA solution, vibrated for 5.0 min and filtered (Scomberomorus niphonius) of 30 − 35 cm in body length through a Whatman 1.0 filter paper (0 − 4℃). The filtrate with 400 − 500 g in body weight were bought at the Nan- (5.0 mL), referred as sample extract, was placed in a 25-mL zhen fishing port in Zhoushan city, China. The fish samples colorimetric tube. To the sample extract, 10.0 mL of 10% (about 200 fish, be stiff in) were kept in ice and transported (v/v) formaldehyde solution, 10.0 mL of anhydrous toluene immediately to the laboratory. The following preparation and 10.0 mL of 7.2 mol/L potassium carbonate solution were process was carried out in a cold room at a temperature of 0 added. The mixture was shaken for approximately 1.0 min, − 4℃. The fresh fish (K-value about 7.0%) were carefully and left to stand for another 20.0 min. Five milliliters from packed in polyethylene bags and divided into four treatment the toluene layer were transferred into a dry tube contain- batches for storage at 5, 0, −20 and −55℃, respectively. ing 5.0 mL of 0.02% (w/v) picric acid toluene solution and Before being analyzed, frozen samples (−20℃ and −55℃) measured using a spectrophotometer (UV 2102 PC, UNICO, were thawed overnight at refrigerator temperature (4℃). The Shanghai, China) at 410 nm. samples stored at 5 and 0℃ were randomly taken and ana- Texture profile analysis Texture profile analysis (TPA) lyzed every day, while the samples stored at −20 and −55℃ of the fish was measured by using a texture analyzer (TMS- were randomly chosen and analyzed every ten days. The PRO, FTC, Sterling Virginia, USA). The sample was place fish were headed and filleted manually using a sterile scalp on the instrument’s platform and a P/50 cylindrical Perspex and forceps. Specimens of dorsal ordinary muscles (taken probe (50 mm diameter) was selected to simulate chewing from three fish) with lapse of time were used for pH, TVBN, process. TPA was performed with the following conditions: TMA and volatile flavor measurements. Each property was constant test speed 1.0 mm/s, sample deformation 30%, hold conducted at least three times in a randomized design and all time between cycles 3.0 s, and trigger force 0.05 N. Tex- measurements were carried out at least twice. ture analysis parameters were calculated using FTC-PRO pH measurement The pH value of fish muscle was de- software (FTC, Sterling Virginia, USA) from the force-time termined according to the method of Benjakul et al. (1997). curves generated from each sample as described by Bourne Ten grams of each sample were blended with 40 mL of (1978). distilled water in a blender (T18 ULTRA–TURRAX, IKA, Electronic nose analysis Electronic nose determination Staufen, Germany) for 60 s at 0 − 4℃. The pH value of was performed with a PEN3 instrument (Airense, Schwerin, Quality Assessment of Mackerel Fish 749 Germany). Processed fish muscle samples were cut into pH of fresh mackerel had a value of 6.12, which increased uniform pieces of approximately 5.0 g, and filled into a 10- significantly to 7.11 in samples stored at 5℃ on the 6th day mL vial which was kept at room temperature (25 ± 2℃) and to 6.96 in samples stores at 0℃ on the 7th day.