Indole production and deepwater pink shrimp (Parapenaeus longirostris) decomposition

Indole levels have been used to confirm the sensory evaluation of shrimp decomposition and a limit of 250 g/kg has been used in several countries to differentiate passable shrimp from shrimp in the first state of decomposition. However, no data exist on the correlation between sensory quality and indole content in deepwater pink shrimp (Parapenaeus longirostris) which validate the use of this defect level. The sensory, microbiological and biochemical changes were determined in microbiologically contaminated (4 and 7 log cfu/g ) deepwater pink shrimp stored at 0, 5, 10 and 15°C. Indole, TMA-N, TVB-N, pH, TVC, Enterobacteriaceae and Pseudomonas spp. increased with time and temperature. At low temperature storage, final indole levels in severely decomposed shrimp (TVB > 60 mg/kg) were much lower than the suggested defect level of 250 g/kg shrimp. Increased microbiological contamination (7 log cfu/g) induced faster and higher indole production at all temperatures. At higher storage temperatures, indole formation was greatly accelerated resulting in very high indole levels. High indole levels indicate decomposition; however decomposed shrimp may not necessarily contain indole. The shelf life of shrimp ranged from 15 h at 15°C to 6 days at 0°C. An indole defect level >90 g/kg shrimp should be used for deepwater pink shrimp.     

Changes in 4-hexylresorcinol residues during processing of deepwater pink shrimp (Parapenaeus longirostris)

Hexylresorcinol has been used as an alternative to sulphites for prevention of melanosis or black-spot of the shrimp carapace. In order to estimate consumption of 4-hexylresorcinol, residual levels have been evaluated in deepwater pink shrimp (Parapenaeus longirostris) following dip treatments and different processing technologies (freezing, cooking and washing). The effect of 4-hexylresorcinol on the microbial growth in the dipped shrimp as well as change in the inhibitory solution during repeated utilization was also followed. The use of 4-hexylresorcinol at concentrations of 0.10 or 0.25 mg/kg led to the detection in pink shrimp of residue levels considerably higher than the limit level of 2 mg/kg. Furthermore, the processing technologies studied also showed a very low efficiency in the reduction of residues from the initial loads to acceptable values. Though the tested initial bacterial load of the shrimp was higher than it is normally expected onboard the solution of 4-hexylresorcinol did not evidence any tendency for an increase of the bacterial counts even after 29 h of utilization. No decrease in the 4-hexylresorcinol concentration is visible even after 8 dips and 29 h of solution use.     

Effect of age and cut on cooking loss, juiciness and flavour of South African beef

The juiciness and flavour characteristics of 15 aged primal beef cuts of electrically stimulated carcasses, from three different age groups, were assessed (n=61). Cooking losses were determined and proximate analyses (moisture, fat, nitrogen and ash) were performed. Tender cuts were cooked by a dry heat method, and less tender cuts were cooked by moist heat methods. A trained panel (n=10) evaluated sensory quality characteristics including initial and sustained juiciness, aroma and flavour. Flavour intensity was the biggest discriminant between the three age groups and declined with an increase in age. Initial impression of juiciness decreased with increased age of the animal and cooking losses increased nonlinearly with age, irrespective of the muscle. In contrast sustained juiciness increased with increased age. Cuts cooked according to a dry heat cooking method were reported juicier (both initial and sustained) than those cooked by moist heat methods.     

Melanosis inhibition and 4-hexylresorcinol residual levels in deepwater pink shrimp (Parapenaeus longirostris) following various treatments

Inhibition of melanosis was studied in pink shrimp (Parapenaeus longirostris) treated on shipboard with various concentrations of 4-hexylresorcinol (4-HR)-based formulations. Treatments, applied by dipping and dusting, were carried out at sea immediately following the catch. A selection of the most effective treatments was made to determine the level of 4-HR residues in the muscle and viscera. 4-Hexylresorcinol proved effective at extending shelf-life over that of untreated shrimp at all the concentrations tested. However, the minimum dose of 4-HR to avoid melanosis for at least one week was found to be 0.5%, with a residual level in muscle ranging from ≈80 to 90 mg/kg at day 2 of storage to >200 mg/kg after 7 days. Residues around 2–3 mg/kg were shown to be effective to prevent melanosis in pink shrimp only for 2 days from a commercial point of view.     

Stereoisomeric flavour compounds LXXVI: direct enantioseparation, structure elucidation and structure-function relationship of 4-tert-butyl-α-methyldihydrocinnamaldehyde

 Using enantioselective gas chromatography and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin (DIAC-TBDMS-β-CD) as the chiral stationary phase, the direct enantioseparation of 4-tert-butyl-α-methyldihydrocinnamaldehyde was achieved. The threshold values and odour characteristics of the enantiomers were investigated by enantioselective gas chromatography/olfactometry. In order to elucidate stereochemical features, the carbonyl-function was oxidized to the corresponding acid and diastereomeric amides were generated with (S)-2-amino-2-phenyl-ethanol [L(+)-α-phenylglycinol] as the enantiopure reagent. After separation and isolation by high-performance liquid chromatography, absolute configurations were deduced from X-ray structure elucidation of a pure stereoisomer. Amide cleavage, reduction and selective oxidation yielded the enantiomers of 4-tert-butyl-α-methyldihydrocinnamaldehyde. Received: 7 October 1996 / Revised version: 18 November 1996     

Influence of heat treatment on carnosine, anserine and free amino acid composition of beef broth and its role in flavour development

 In an attempt to determine the most important free amino acids (FAAs) in the development of the flavour of beef broths, the amino acid compositions of beef broths prepared at different temperatures and cooking times, with flavours of different intensities, were studied. From our data, broths obtained at temperatures above 75  °C and cooking times longer than 120 min had significantly lower levels of most of the FAAs studied (P<0.05). Statistical analysis of the sensorial and analytical data (principal component analysis, chi-square analysis) permitted the different FAAs to be grouped in relation to the flavour. There was a significant association between elevated levels of glutamic acid, asparagine (P<0.01), lysine and methionine (P<0.05) and the development of beef broth flavour. However, this was inversely related to levels of cysteine, proline, serine, M-histadine, tyrosine, valine, arginine and aspartic acid whereas reduced levels of β-alanine, asparagine, tyrosine, threonine, methionine, cysteine, leucine, isoleucine, tryptophan, glutamic acid, histidine, lysine and phenylalanine were associated with sapid properties not characteristic of beef broths (astringent, warmed-over flavours). A significant correlation (P<0.01) between sensory evaluation and carnosine and anserine levels was also observed. Received: 29 December 1998 / Revised version: 29 April 1999     

The effect of several cooking treatments on subsequent chilled storage of thawed deepwater pink shrimp (Parapenaeus longirostris) treated with different melanosis-inhibiting formulas

This work deals with the effect that different cooking methods have on quality of shrimps (Parapenaeus longirostris) during the chilled storage. Vacuum-cooking (sous-vide) and steaming were compared with the traditional cooking process in boiling water. The effect of prior treatment with several melanosis-inhibiting agents (with a commercial sulphite- or 4-hexylresorcinol-based formula) was also tested. Neither the melanosis-inhibiting blends nor the cooking methods used significantly affected the water-holding capacity, firmness or moisture content of the cooked shrimps. Spraying with a 4-hexylresorcinol-based formula was effective in preventing microbial growth during storage. Vacuum-cooking was also shown to be the most effective way of preventing microbial growth although the TVB-N content of cooked shrimps increased significantly. By discriminant analysis, a combination of prior spraying with 4-hexylresorcinol-based formula followed by vacuum-cooking, proved to be the best method for obtaining shrimps with a very good appearance and high microbial quality. The foregoing may be very important for the cooking industries.     

Onboard processing of deepwater pink shrimp (Parapenaeus longirostris) with liquid ice: Effect on quality

This study investigated the effect on the quality of deepwater pink shrimp (Parapenaeus longirostris) of onboard chilling with liquid ice versus the traditional chilling with flaked ice. Quality was estimated by physical, chemical, microbiological and sensory parameters after 24 h and 4 days of chilled storage. Application of liquid ice immediately after catch for the fast chilling of pink shrimp reduced the formation of nitrogenous compounds and slowed down the increase in pH and the development of microorganisms during iced storage. On the other hand, texture (breaking force, hardness and elasticity) showed only minor changes. Pink shrimp chilled with liquid ice showed, however, loss of characteristic bright colours and development of dull tones in the carapace that depreciates the product's commercial value. Nevertheless, application of liquid ice onboard was advantageous over the utilization of the traditional type of ice, and seems particularly applicable when shrimp is to be used as a raw material for the type of processing that requires elimination of the carapace.     

Several melanosis-inhibiting formulas to enhance the quality of deepwater pink shrimp (Parapenaeus longirostris)

The aim of this work was to assess the effect of several melanosis-inhibiting formulations on quality of deepwater pink shrimp (Parapenaeus longirostris) during storage. The formulations tested were as follows: one containing 4-hexylresorcinol (0.1%) in combination with organic acids (citric, ascorbic and acetic) and chelating agents (ethylenediaminetetraacetic acid [EDTA] and di-sodium di-hydrogen pyrophosphate [PPi]); a commercial formula based on sulphites (3%), and another formulation containing a mixture of chitosan (0.3%) and commercial sulphites. Non-treated shrimp were used as control. The 4-hexylresorcinol-based formulation was more effective than 3% of commercial sulphite solutions in preventing melanosis. This treatment prolonged the sensory acceptability of shrimp by up to six days in ice storage. During chilled storage, the treatment with the 4-hexylresorcinol-based formula inhibited the growth of microorganisms by 1.5–2 log cycles as compared to commercial sulphites, especially H₂S-producers and pseudomonads. At the end of the experimental period, TVB-N levels were slightly higher in the lot treated with 4-hexylresorcinol (33 mg/100 mg) and reflected greater endogenous enzymatic activity, since the counts of the spoiler microorganisms remained around log 5 cfu/g or even lower. In general, the incorporation of chitosan to sulphites did not improve or produce a marked effect on shrimps during storage. During the sensory analysis, the panellists rated all the lots very similar, although the 4-hexylresorcinol formulation was the only one with a neutral odour at the end of the period. The 4-hexylresorcinol-based formulation induced yellow-green colorations to some extent in the cephalothorax, possibly due to the effect of organic acids and chelants, while the rest of the lots presented greyish/blackish colorations. Therefore, the formulation based on 4-hexylresorcinol may safely substitute traditional sulphites to improve the quality of fresh shrimp and prolong their shelf life during storage.     

Changes in the profile of volatile compounds in wines stored under oxygen and their relationship with the browning process

 Eight young white wines produced in Aragon from Macabeo and Chardonnay grapes were stored under an oxygen atmosphere in the dark at room temperature. Changes in the colour and volatile compound composition were recorded over a period of 13 weeks. Significant changes in the volatile compound composition were detected through analysis of variance (ANOVA) of repeated measures, considering both grape variety and browning tendency as discriminant categories. The amounts of fatty acids and fermentation esters in the wine were significantly changed by the oxidative storage. Some of these changes can be attributed to acid-ester hydrolysis equilibria, but not others, such as the decrease in concentrations of octanoic and decanoic acids. The oxidative storage also affected most of the unsaturated fatty-acid-derived compounds: trans-2-octenal, trans-2-nonenal, trans-2-decenal and 1-octen-3-ol were all found to increase in the first stages of storage, while hexanol decreased slightly. Volatile phenols behaved very differently: while phenol and 4-ethylphenol initially increased and later decreased, eugenol increased through the process and 4-vinyl-guaiacol disappeared. Benzaldehyde and furfural increased while methionol and terpenols disappeared. Only furfural was found to be linked with the tendency of the wine to brown, while only linalool and benzaldehyde were found to be linked whith the grape variety. The levels of some odorants previously isolated by sniffing detection were temptatively monitored, and significant changes in their concentrations were found to occur during the process. Received: 16 December 1996 / Revised version: 27 March 1997     

Changes in the profile of volatile compounds in wines stored under oxygen and their relationship with the browning process

 Eight young white wines produced in Aragon from Macabeo and Chardonnay grapes were stored under an oxygen atmosphere in the dark at room temperature. Changes in the colour and volatile compound composition were recorded over a period of 13 weeks. Significant changes in the volatile compound composition were detected through analysis of variance (ANOVA) of repeated measures, considering both grape variety and browning tendency as discriminant categories. The amounts of fatty acids and fermentation esters in the wine were significantly changed by the oxidative storage. Some of these changes can be attributed to acid-ester hydrolysis equilibria, but not others, such as the decrease in concentrations of octanoic and decanoic acids. The oxidative storage also affected most of the unsaturated fatty-acid-derived compounds: trans-2-octenal, trans-2-nonenal, trans-2-decenal and 1-octen-3-ol were all found to increase in the first stages of storage, while hexanol decreased slightly. Volatile phenols behaved very differently: while phenol and 4-ethylphenol initially increased and later decreased, eugenol increased through the process and 4-vinyl-guaiacol disappeared. Benzaldehyde and furfural increased while methionol and terpenols disappeared. Only furfural was found to be linked with the tendency of the wine to brown, while only linalool and benzaldehyde were found to be linked whith the grape variety. The levels of some odorants previously isolated by sniffing detection were temptatively monitored, and significant changes in their concentrations were found to occur during the process. Received: 16 December 1996 / Revised version: 27 March 1997     

Effect of fat content on flavour release from sausages

The influence of fat content (5%, 10% and 15%) of sausage on the release of 10 volatile compounds with different physicochemical properties (log P and log ρL ranged between 1.01 and 4.23, and −0.66 and 1.69, respectively) was studied under static headspace (raw and cooked sausages) and in-mouth conditions (cooked sausages). Increasing fat content caused a general increase in the volatile compound concentrations of the sausages (fat acted as a reservoir) but a decrease in the compound concentration in the headspace and in the nosespace. The opposite effect was found for 3-methylbutanal and ethyl-2-methylbutanoate, which are more polar (low values for log P) and volatile (large values for log ρL) than the other compounds. Static headspace data revealed that the effect of fat content was larger in the raw samples than in the cooked sausages. The time to reach the maximum response for the compounds in the nosespace during mastication was not affected by fat content.     

Effect of different cooking methods on the flavour constituents of mushroom (Agaricus bisporus (Lange) Sing) soup

The effect of different cooking methods on the flavour of mushroom soup was assessed. The results indicated that the levels of free amino acids and 5’‐nucleotides in the microwaved mushroom soup were (P < 0.05) higher than those in boiled and autoclaved mushroom soup. The number of volatile compounds identified in the boiled mushroom soup was (P < 0.05) higher than those in autoclaved and microwaved mushroom soup. The main aroma‐active compounds found in mushroom soup were 1‐octen‐3‐one (mushroom‐like), 3‐octen‐2‐one (cooked mushroom‐like), 2,6‐dimethyl pyrazine (roast nut), benzeneacetaldehyde (floral), dihydro‐5‐methyl‐2(3H)‐furanone (sweet) and some unknown compounds with popcorn and sauce flavour. In addition, boiled, autoclaved and microwaved mushroom soup possessed thirteen, ten and nine aroma‐active compounds (with flavour dilution factors > 1), respectively. Thus the flavour of mushroom soup is dependent on the cooking methods as proved by gas chromatography and olfactometry analysis.     

Effect of different chemical compounds as coadjutants of 4‐hexylresorcinol on the appearance of deepwater pink shrimp (Parapenaeus longirostris) during chilled storage

Different chemical compounds (kojic acid, cumic acid, phytic acid, sodium metabisulphite, magnesium carbonate, sorbic acid and different protease inhibitors) were used as coadjutants in 4‐hexylresorcinol (4‐HR)‐based melanosis‐inhibiting formulas tested for inhibiting melanosis in pink shrimp (Parapenaeus longirostris). The experiment was performed on board ship. Increasing concentrations of 4‐HR delayed the occurrence of melanosis during storage. However, 4‐HR could not prevent the appearance of a yellow‐greenish colouration in the cephalothorax that diminishes the consumer acceptability of shrimps. The incorporation of protease inhibitors (ethylenediaminetetraacetic acid, disodium dihydrogen pyrophosphate, iodoacetic acid, egg white and phenylmethylsulphonyl fluoride) into the 4‐HR‐based mixtures improved the acceptability after storage, suggesting that protease activity post‐mortem contributes to the reduction in the final acceptability of crustaceans.     

Indole levels in deepwater pink shrimp (Parapenaeus longirostris) from the Portuguese coast. Effects of temperature abuse

Deepwater pink shrimp (Parapenaeus longirostris) is an important commercial species in Portugal with a catch volume over 1000 tons and a high market value, estimated in 2000 as being equivalent to 11 million Euros. Indole levels have been used to confirm the sensory evaluation of shrimp decomposition and a limit of 250 µg/kg has been used in several countries to differentiate passable shrimp from shrimp in the first stage of decomposition. No data exist on indole levels in this species and taking into account that a considerable amount of the catches are exported as fresh to Spain, it was necessary to evaluate the indole production in order to identify the usefulness of this index as an indicator of temperature abuse in this species. Biochemical, physico-chemical, microbiological and sensory changes were evaluated in fresh deepwater pink shrimp stored at 2 °C and at room temperature (22 °C). Cooked deepwater pink shrimp chill-stored was studied too. The results indicated that indole was produced at levels of 167 µg/kg when raw shrimp was chill-stored for 7 days, while levels around 7400 µg/kg were produced after 32 h in raw shrimp stored at room temperature. Indole production of deepwater pink shrimps, showed a close parallel with microbiology data, mainly with Enterobacteriaceae production. We concluded that, in the conditions studied, the indole could be considered a useful indicator in assessing the history of shrimp if high temperature is suspected or bad hygiene conditions have been applied. Nevertheless, a low content of indole does not necessarily imply good quality.     

Trace elements in edible tissues of three shrimp species (Penaeus semisulcatus,Parapenaeus longirostris and Paleomon serratus)

Accumulation levels of trace elements in edible tissues of three shrimp species (Penaeus semisulcatus, Parapenaeus longirostris and Paleomon serratus) from the Gulf of Antalya, Turkey were investigated. Copper (Cu), cadmium (Cd), zinc (Zn), iron (Fe) and manganese (Mn) concentrations were determined by atomic absorption spectrophotometry. The lowest Cu (1.33 mg kg^?1) and Cd (0.23 mg kg^?1) and highest Mn (1.52 mg kg^?1) concentrations were found in P. longirostris, the lowest Zn (6.25 mg kg^?1), Fe (1.84 mg kg^?1) and Mn (0.25 mg kg^?1) concentrations in P. serratus and the highest Cu (6.19 mg kg^?1), Cd (2.36 mg kg^?1), Zn (30.84 mg kg^?1) and Fe (33.89 mg kg^?1) concentrations in P. semisulcatus. The Cd levels detected in P. semisulcatus and P. serratus were above legislative limits. Our results show that there were significant differences in trace element concentrations among the three shrimp species. The highest levels of the five trace elements investigated, with the exception of Mn, were found in edible tissue of P. semisulcatus. Copyright © 2007 Society of Chemical Industry     

Nutritional quality of red shrimp,Aristeus antennatus (Risso), pink shrimp,Parapenaeus longirostris (Lucas), and Norway lobster,Nephrops norvegicus (Linnaeus)

The proximate composition, amino acid and fatty acid profiles, lipid classes and cholesterol and glycogen contents were determined in the edible part of red shrimp, Aristeus antennatus (Risso), pink shrimp, Parapenaeus longirostris (Lucas), and Norway lobster, Nephrops norvegicus (Linnaeus), in two distinct periods of the year. The proximate composition did not vary significantly between species or between periods of sampling. Significant differences in glycogen content were obtained between winter and summer; the lowest values were attained in winter (1.2, 1.1 and 1.0% wet weight for red shrimp, pink shrimp and Norway lobster respectively). With the exception of Norway lobster, an opposite trend was obtained for cholesterol content, ie lower values in summer (60.8 and 57.8 mg per 100 g wet weight for red shrimp and pink shrimp respectively). The major essential amino acids (EAA) were arginine, lysine and leucine and the limiting amino acid was methionine in all three crustacean species. The most important non‐essential amino acids (NEAA) were glutamic acid, aspartic acid, proline and glycine. In respect to lipid classes, phospholipids and free cholesterol predominated. The major fatty acids were 16:0, 18:1n‐9, 20:5n‐3 and 22:6n‐3. The polyunsaturated fraction was dominant (42.1–48.4%), followed by the monounsaturated (26.3–34.6%) and saturated (22.9–27.4%) fatty acids. In conclusion, the nutritional quality of these shellfish species is similar, they are valuable protein and lipid sources for the human diet and are adequate elements of the traditional Portuguese diet. Copyright © 2003 Society of Chemical Industry     

Effect of sampling fat location and cooking on fatty acid composition of beef steaks

To investigate the impact of sampling fat location and cooking on fatty acid composition of beef steaks, 21 raw steaks from crossbred steers were dissected to obtain outer (OSC) and inner subcutaneous fat (ISC), seam fat, marbling, and lean muscle. Twenty-one cooked steaks were dissected to obtain OSC, ISC, seam fat, surface and inner muscle. Trans-vaccenic acid and c9, t11-CLA percentages were lower (P < 0.05) in lean muscle than subcutaneous (s.c.) fat or marbling. Monounsaturated: saturated fatty acid ratios were lower (P < 0.05) in seam fat and marbling than s.c. fat or lean muscle. Linoleic and linolenic acid levels were highest in lean muscle and longer chain n−6 and n−3 fatty acids were only detected in lean muscle. Cooking did not change fatty acid composition dramatically except that n−6: n−3 ratio in s.c. and seam fat decreased after cooking (P < 0.05).