The Effect of Stunning Methods on Rigor Mortis and Texture Properties of Atlantic Salmon (Salmo Salar)

Shear force and rigor mortis were used to evaluate the post‐mortem changes of muscle texture in Atlantic salmon (Salmo salar). The fish were either stunned with carbon dioxide (CO₂), electricity, or percussion prior to slaughter. The pre‐mortem stress during CO₂ stunning resulted in an earlier onset and resolution of rigor mortis, and accelerated post‐mortem softening of the muscle tissue as compared to the other stunning methods. No significant differences, either in development of rigor mortis or shear force, were seen between fish that were stunned with electricity or by percussion. Consequently electricity can be used for stunning fish prior to slaughter.     

The Effect of Stunning Methods and Season on Muscle Texture Hardness in Atlantic Salmon (Salmo salar L.)

Commercially collected records of Atlantic salmon (Salmo salar L.) muscle texture hardness were used to evaluate the effect of slaughter procedures and seasonality on texture quality. A database collected by Marine Harvest® contained flesh hardness records of Atlantic salmon slaughtered at processing plants in Norway from summer 2010 to summer 2011. The fish were slaughtered either by (1) percussion followed by automated bleeding (“Percussive”) or (2) live chilling with exposure to carbon dioxide (CO₂) followed by manual severing gill arches and bleeding (“CO₂”) or (3) live chilling with exposure to CO₂ followed by percussive stunning and at the end automated bleeding (“CO₂·percussive”). Hardness in salmon muscle cutlets was measured in Newtons (N) by Materials Testing Machine Zwick 500N. The hardness in salmon varied significantly over the study period (P < 0.05, mixed effect model) and showed the softest value of 21.2 (± 0.7) Newton (N) in summer 2011 and hardest 24.1 (± 0.2) N in autumn 2010. Slaughter procedures had a significant effect on salmon muscle hardness (P < 0.05, mixed effect model), where percussion followed by automated bleeding resulted in the hardest value (24.0 ± 0.4 N) as compared with CO₂ stunning (21.8 ± 0.2 N) and combination of CO₂ and percussive stunning (23.1 ± 0.15 N). CO₂ is suspected as a causal factor in accelerated postmortem softening of the salmon muscle.     

Quorum Sensing Involved in the Spoilage Process of the Skin and Flesh of Vacuum‐Packaged Farmed Turbot (Scophthalmus maximus) Stored at 4 °C

Fish skin has both positive and negative effects on the shelf‐life of the fish. This study aimed to investigate the spoilage process of the skin and flesh of refrigerated farmed turbot (Scophthalmus maximus) with vacuum packaging. Microbial community changes were analyzed by combining culture‐dependent and culture‐independent methods. The results indicated that the shelf‐life of vacuum‐packaged refrigerated turbot was 16 d; skin mucus was the interference factor of turbot quality. The culture‐dependent analysis demonstrated that the total viable counts and the population of H₂S‐producing bacteria, Pseudomonas spp., Enterobacteriaceae spp., and lactic acid bacteria in skin had a range of 0.45 to 1.40 log (CFU/g) higher than the microbial numbers in flesh after 16 d in storage. 16S high throughout sequencing results demonstrated that the compositions of spoilage microbes were similar in skin and flesh. Shewanella spp., followed by Carnobacterium spp., was the dominant spoilage organism at day 16. Quorum sensing (QS) signaling activity increased during the storage. Exogenous N‐butanoyl‐L‐homoserinelactone(C4‐HSL) and N‐hexanoyl‐Lhomoserine lactone (C6‐HSL) significantly accelerated the spoilage process of refrigerated turbot, while the addition of 4, 5‐Dihydroxypentane‐2, 3‐dione (DPD) prolonged the lag phase duration. Therefore, QS may be involved in the spoilage process of refrigerated turbot.     

Aktivit?t und subcellul?re Verteilung einiger Mitochondrien-Enzyme im Skeletmuskel. III. Einflu? des Gefrierens und Auftauens von Rindermuskel

Zusammenfassung Proben desM. Longissimus-dorsi des Rindes wurden vor und nach Eintreten desrigor mortis bei –20° C eingefroren und bei Zimmertemperatur aufgetaut. Die Änderung der mit Phosphatpuffer extrahierbaren Aktivität der Mitochondrien-enzyme Aconitase (AC), Fumarase (FU), Glutamatdehydrogenase (GLDH), Malatdehydrogenase (MDH) und Succinodehydrogenase (SDR) durch Gefrieren und Auftauen wurde studiert. Gefrieren und Auftauen führten zu keiner wesentlichen Änderung der extrahierbaren Aktivität der untersuchten Enzyme, jedoch zu einer Zunahme der SDH-Aktivität im nicht zentrifugierten Muskelhomogenat.Durch Bestimmung der Enzymaktivitäten im Preßsaft des unzerkleinerten Muskels wurde die subcelluläre Verteilung der Enzyme ermittelt. Gefrieren des Muskels vor und nach Eintritt desrigor mortis und Auftauen bewirkten eine Freisetzung von AC, FU und MDH aus ihrer Bindung an die mitochondrialen Membranen. GLDH, ein Enzym der mitochondrialen Matrix, trat bei Gefrieren des Gewebes vor Eintritt desrigor mortis und Auftauen in das Sarkoplasma über; nach Eintritt desrigor mortis war GLDH bereits ohne Gefrierenfreigesetzt. Die Freisetzung der Enzyme beruht offenbar auf einer Schädigung der Mitochondrien-membranen durch Gefrieren und Auftauen. Eine völlige Desintegration der Membranen scheint jedoch nicht einzutreten, da weder die subcelluläre Verteilung noch die Gesamtaktivität von SDH durch den Gefrierprozeß verändert werden. Wiederholtes Gefrieren und Auftauen hatte nur bei AC eine verstärkte Freisetzung des Enzyms zur Folge. Diese Resultate werden im Hinblick auf elektronenmikroskopische Befunde anderer Autoren diskutiert.Der Einfluß desrigor mortis (ohne Gefrieren) auf Gesamtaktivität und subcelluläre Verteilung der Enzyme war der gleiche wie er in einer vorangehenden Untersuchung beobachtet worden war.

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Activity and subcellular distribution of some mitochondrial enzymes in skeletal muscle. III. Influence of freezing and thawing of bovine muscle

Summary Samples of bovine muscle were frozen at –20° C before and after onset ofrigor mortis and subsequently thawed at room temperature. The changes in the extractable activity of the mitochondrial enzymes aconitase (AC), fumarase (FU), glutamic dehydrogenase (GLDH), malate dehydrogenase (MDH), and succinic dehydrogenase (SDH) by freezing and thawing were determined. Freezing and thawing did not cause significant changes in the extractable activities of all the enzymes investigated, but did increase the SDH activity in the non-centrifuged muscle homogenate.The subcellular distribution of the mitochondrial enzymes was investigated by determination of the enzyme activities in the press-juice of the intact muscle. Freezing of the muscle before and after onset ofrigor mortis and subsequent thawing caused a release of AC, FU, and MDH from the mitochondrial membranes. GLDH, an enzyme of the mitochondrial matrix also went into the sarcoplasma when freezing the tissue before the onset ofrigor and thawing; afterrigor this enzyme was already released without freezing. The release of these enzymes indicates some damage of mitochondrial membranes due to freezing and thawing. A complete disintegration of the membranes, however, did not occur because the activity and the subcellular distribution of SDH was not changed by freezing and thawing. Repeated freezing and thawing of the tissue resulted in an increased release of AC only. These results are discussed with regard to electron microscopic studies of other authors.The influence ofrigor mortis (without freezing) on the activity and subcellular distribution of the mitochondrial enzymes was the same as observed in a previous investigation.

     

Using the Essential Oil of Aloysia triphylla (L'Her.) Britton to Sedate Silver Catfish (Rhamdia quelen) during Transport Improved the Chemical and Sensory Qualities of the Fish during Storage in Ice

Exposure of silver catfish to 40 μL/L of the essential oil of Aloysia triphylla (AT) during in vivo transport delayed the onset and resolution of rigor mortis as well as the degradation of IMP into HxR compared to the control. The fish that were treated with 30 or 40 μL/L of AT received lower sensory demerit scores after 10 d of storage in ice compared to the control, and the fish that were treated with 40 μL/L of AT had a longer sensory shelf life than did the control. These results indicated that using AT as a sedative in the water in which the silver catfish were transported extended their freshness and increased their shelf life during refrigerated storage.     

Effects of Chilling and Partial Freezing on Rigor Mortis Changes of Bighead Carp (Aristichthys nobilis) Fillets: Cathepsin Activity,Protein Degradation and Microstructure of Myofibrils

To investigate the effects of chilling and partial freezing on rigor mortis changes in bighead carp (Aristichthys nobilis), pH, cathepsin B, cathepsin B+L activities, SDS‐PAGE of sarcoplasmic and myofibrillar proteins, texture, and changes in microstructure of fillets at 4 °C and –3 °C were determined at 0, 2, 4, 8, 12, 24, 48, and 72 h after slaughter. The results indicated that pH of fillets (6.50 to 6.80) was appropriate for cathepsin function during the rigor mortis. For fillets that were chilled and partially frozen, the cathepsin activity in lysosome increased consistently during the first 12 h, followed by a decrease from the 12 to 24 h, which paralleled an increase in activity in heavy mitochondria, myofibrils and sarcoplasm. There was no significant difference in cathepsin activity in lysosomes between fillets at 4 °C and –3 °C (P > 0.05). Partially frozen fillets had greater cathepsin activity in heavy mitochondria than chilled samples from the 48 to 72 h. In addition, partially frozen fillets showed higher cathepsin activity in sarcoplasm and lower cathepsin activity in myofibrils compared with chilled fillets. Correspondingly, we observed degradation of α‐actinin (105 kDa) by cathepsin L in chilled fillets and degradation of creatine kinase (41 kDa) by cathepsin B in partially frozen fillets during the rigor mortis. The decline of hardness for both fillets might be attributed to the accumulation of cathepsin in myofibrils from the 8 to 24 h. The lower cathepsin activity in myofibrils for fillets that were partially frozen might induce a more intact cytoskeletal structure than fillets that were chilled.     

Effect of Slaughter Method on Postmortem Changes of Grass Carp (Ctenopharyngodon idella) Stored in Icesti

ABSTRACT: The effect of 2 slaughter methods (immersion in ice-water slurry and electrical stunning followed by ice slurry asphyxiation) on the quality of grass carp ( Ctenopharyngodon idella ) stored in ice for 20 d was evaluated using sensory and chemical analysis. Electricity immediately stunned the fish and did not induce blood spots in the flesh. Fish killed by electricity showed a faster initial rate of ATP degradation and entered into rigor mortis earlier, but did not show significant differences in the sensory score when compared with fish killed by immersion in ice-water slurry. Thus, no differences were observed in the shelf life of carps between the 2 slaughter methods evaluated. The limit for acceptability of grass carp stored in ice was around 13 to 16 d. Grass carp accumulated more inosine than hypoxanthine. K, Ki, P , Fr, and H values were highly correlated with storage time and with the TFRU sensory scores in both groups; these could be used to assess the freshness quality of grass carp.     

The influence of death struggle on the rate of glycolysis in chicken breast muscle

Experiments were conducted to study the effect of killing procedures on the biochemical metabolites of broiler chicken breast muscle. The degree of struggle at death profoundly affected the onset of rigor mortis both in intact carcases and in muscles stored off the bird. Evidence was obtained that the amount of ATP present in the muscle, and hence the time of onset of rigor, could be estimated by measurement of the pH value of the muscle.     

The effects of carbon monoxide on Atlantic salmon (Salmo salar L.)

Atlantic salmon were exposed to carbon monoxide (CO) before the fish were percussively killed and gill cut. The fish were compared against a control group treated identically, without CO. Salmon exposed to CO expressed no adverse reactions and were easily stunned by percussion. CO-treated salmon had an earlier onset of rigor mortis and a faster decrease in muscle pH than the control group. No significant difference in drip loss was found between salmon treated with CO and the control. A significantly deeper red colour of both gills and fillets of CO-treated salmon was observed 10 days post mortem. Significantly higher levels of plasma lactate and potassium were found in CO-treated salmon compared to control, as well as a lower level of pCO₂. Exposure to CO did not increase plasma cortisol, sodium, haematocrit or glucose; however, lactate was high. Exposure of salmon or other fish to CO could improve quality and welfare when slaughtered.     

Flesh Quality in Snapper, Pagrcrs auratus, Affected by Capture Stress

Muscle metabolites in resting, tank acclimated snapper, Pagrus auratus, were monitored for 72 hr postmortem and compared with values from exercised or commercially caught fish. The physiological status of the live animal was quantified by plasma cortisol and blood chemistry. Cortisol levels were lowest in unstressed controls (6.8 ± 2.1 ng mL^?1) while exercised laboratory fish had highest levels (67.7 ± 11.2 ng mL^?1). Control fish maintained a constant K-value for 72 hr in chilled storage; all other groups had significant increases. Onset of rigor development and muscle ATP depletion was delayed in unstressed fish and was more rapid in line-captured than exercised fish. Commercial users minimizing stress would maintain high flesh quality.     

Fruit calcium concentration and chilling injury during low temperature storage of pineapple

The concentration of calcium and its distribution in different parts of the fruit were determined in Queen‐type Mauritius and Cayenne‐type Kew pineapple varieties. Calcium content was measured before and after storage for 17 days at 10 °C followed by 2 days at 28 °C. Total calcium concentrations were significantly (p < 0.05) higher in Kew than in Mauritius pineapple. This difference corresponded to a significantly (p < 0.05) lower incidence of chilling injury in the former. The calcium content in fruits at harvest was significantly (p < 0.05) higher in the shell region for both varieties. Browning symptoms associated with chilling injury were observed in the core and in the flesh adjacent to the core, where lower concentrations of calcium were recorded. Chilling injury was minimal in the flesh near the shell, where calcium concentrations were significantly (p < 0.05) higher. Following storage, calcium concentrations in the core and flesh regions decreased, while a significant (p < 0.05) increase in concentration was recorded in the shell region of the susceptible Mauritius variety. Copyright © 2003 Society of Chemical Industry     

Water dynamics of turbot flesh during frying,boiling, and stewing processes and its relationship with color and texture properties: Low‐field NMR and MRI studies

Water dynamics in turbot flesh during frying, boiling and stewing was assessed by nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques. Protons associated with different types of water were distinguished by T₂ relaxation spectra, and significant differences of water mobility were detected. Principle component analysis revealed a clear discrimination between samples of different cooking methods. MRI provided further visualization of internal information for turbot flesh during cooking. The linear regression analysis demonstrated a strong correlation between the NMR parameter A₂₃ and b* value (R² = .972) during frying process, A₂₃ and L* (R² = .963), T₂₂ and b* (R² = .991) during boiling process, T₂₂ and b* (R² = .883) during stewing process. Moreover, a good correlation was found between A₂₁ and cohesiveness (R² = .924) during the frying process, A₂₃ and resilience (R² = .879) during boiling process, as well as between A₂₃ and chewiness (R² = .946) during stewing process.

Practical applications

Water mobility and distribution can significantly affect turbot flesh physical and biochemical status leading to change the texture, color, tenderness and taste during cooking process. Therefore, it is very important to develop a fast, nondestructive method to monitor the water dynamics, reduce the cooking time, save energy and visualize the structure change of turbot flesh during cooking. In this study, a rapid and nondestructive NMR and MRI method were developed to analyze the water dynamics of turbot flesh during frying, boiling and stewing for the first time. The water states, distribution and mobility were analyzed by the NMR and MRI. Different cooking methods displayed different water dynamics in turbot flesh, which could be identified when NMR combined with chemometrics principal component analysis. The facile method by using both NMR and MRI for analysis of turbot flesh may have great potential for rapid and nondestructive analysis of other food processing.     

Tenderness in relation to the temperature of rigor onset in cold shortened beef

Beef sternomandibularis muscle was cold shortened at 2°C for 24 h and then transferred to 37°C until rigor mortis was complete. In spite of a final shortening of 33%, the mean shear value after cooking was identical with that of unshortened meat which had gone into rigor at 15°C. Meat sent into rigor at 2°C with the same degree of shortening had twice the shear value. Thus raising the temperature to 37°C in the final stages of rigor completely nullifies the toughness seen in cold shortened meat, without affecting the shortening. Small changes in cooking loss run parallel to tenderness. The effects are not due to ageing, and may arise from modification of actin–myosin bonding. It is concluded that conditions during the last stages of rigor onset are more important to tenderness than the rest of the post-mortem history of the muscle.     

Effects of essential oils on the survival of Salmonella Enteritidis and Listeria monocytogenes on fresh Atlantic salmons (Salmo salar) during storage at 2 ± 1 °C

In this study, the effects of coriander, garlic, rosemary, and orange peel oils on the survival of Salmonella Enteritidis and Listeria monocytogenes were examined 2 ± 1 °C during storage of inoculated fresh Atlantic salmon samples (96 hr). At the end of storage population decrease in Salmonella Enteritidis was significantly lower (p < .05) in the essential oil groups compared with control group. Salmonella Enteritidis count of rosemary oil treated group was higher than (p < .05) other groups (coriander, garlic, and orange peel oils) at the end of storage. Essential oils decreased the population of L. monocytogenes while the population in untreated samples were higher at the end of storage period (p < .05). Results of this study indicated that treatment of salmon fish samples with essential oils may be an effective natural antimicrobial application to control Salmonella Enteritidis and L. monocytogenes.

Practical applications

In the present study, it was concluded that essential oils had an antimicrobial effect Salmonella Enteritidis and Listeria monocytogenes. Use of essential oils during storage of fish or fish products may play an important role against Salmonella Enteritidis and L. monocytogenes. Essential oils are easily applicable and a cheaper method. The results of this experiment propose that addition of essential oils to fish flesh can be recommended to seafood processors and fish market retailers.     

The connective tissues of fish.

'Gaping' is a phenomenon in which the connective tissues of fish fillets fail to hold the blocks of muscle together. Slits appear across the surface of the muscle which cannot then be mechanically skinned, or, in the case of smoked salmon fillets, sliced.
Seasonal increases in the gaping of salmon fillets coincide with a fall in the postmortem pH of the flesh, occurring in June-July.
Extensive gaping can be caused by fish entering rigor mortis at too high a temperature. In trout, this temperature is considerably higher than in gadoids, suggesting that gaping from high-temperature rigor may in practice be fairly rare in salmonids.
The thermal denaturation temperature ( T _D) of acid-soluble collagen isolated from the turbot farmed in warmed water does not differ significantly from that of the connective tissues of those reared at normal temperatures. This observation is discussed in relation to gaping.     

Gilthead seabream (Sparus aurata): suitability for freezing and commercial alternatives

The quality of portion‐size farmed gilthead seabream (Sparus aurata) during frozen storage and the influence of post‐mortem treatments were studied in order to find new ways of marketing this species. Portion‐sized gilthead seabream, fasted for 48 h prior to slaughter, were frozen and stored at ?20 °C for up to one year. Whole fish were frozen immediately after rigor mortis; gutted fish were frozen immediately after rigor and after 5 days of storage in ice. All lots were stored at ?20 °C for up to one year. The myofibrillar protein of this species was very stable and a slight decrease of solubility in salt solutions was found only after one year of frozen storage. A slight decrease in water‐holding capacity and a slight increase in shear strength were observed, but these were lower than in other species. These changes were reflected as increased toughness and reduced juiciness in sensory analysis of the cooked fillets after one year. The main changes in the cooked fillets were observed in odour and flavour. No significant detrimental effect due to the guts was detected during frozen storage. Storage in ice prior to freezing was reflected in sensory assessment of the raw fish, mainly in terms of initial higher demerit points for fishy odour, gills and eyes; however, no effect was observed in the cooked fillets. Copyright © 2004 Society of Chemical Industry     

Double freezing of cod fillets: Influence on sensory,physical and chemical attributes of battered and breaded fillet portions

Fillet samples were processed on board a research vessel from cod (Gadus morhua) in different states of rigor mortis. In addition, headed and gutted fish in different states of rigor were frozen and, after ten days of frozen storage, the fish were thawed, processed into fillets and refrozen. During subsequent frozen storage at –24°C of breaded and battered portions processed from the different fillet batches several quality attributes were tested using sensory, physical, and chemical methods. The measurements indicated differences in the quality attributes depending on refreezing and rigor states. Especially the sensory texture attributes gumminess and, with some restrictions, firmness were found to be suitable for distinguishing single frozen (SF) from double frozen (DF) samples. This finding was supported by the outcome of the measurement of penetration force where generally a significantly (p < 0.05) higher force was necessary to penetrate the DF compared to SF samples. DF samples were generally lighter (higher L*) than SF samples. The colour difference δE between both sample types was at least very clear and therefore visible. However, no clear differences between SF and DF samples were found when evaluating the flavour attributes and using instrumental texture profile analysis for texture characterisation. Also, all chemical parameters measured did not allow to clearly distinguish between single and double frozen samples. Therefore, it can be stated that, at least when using cod as raw material for processing battered and breaded portions, the different methods for preparing the fillet blocks will, if at all, only affect the textural quality of the final products.     

Distribution of lipids and trace minerals in different muscle sites of farmed and wild turbot (Psetta maxima)

Lipid and trace mineral composition were studied in different sites of the edible flesh of farmed and wild turbot (Psetta maxima). Lipid matter (total content, sterols, tocopherols) showed to accumulate in the edge zone (EZ), except for phospholipid (PL), which provided a distribution that was found to be independent from the kind of turbot and the zone considered. Fatty acid composition of total lipids showed a non‐homogeneous distribution, as the EZ exhibited a different fatty acid group composition (higher monounsaturated and lower polyunsaturated and ω3/ω6 ratio values) than the other zones considered; fewer differences were observed by considering the PL fatty acid composition. Most minerals (Ca, Cu, Fe, Mn and Se) studied showed to be homogeneously distributed along the muscle sites of the wild fish, while more differences were obtained when considering the farmed one. For both kinds of turbots, the most important difference was obtained in the case of Zn, as a largely higher content in the EZ than in the other zones was detected. A close relationship between Zn and total lipid contents (r² = 0.90 and 0.76 for farmed and wild turbots, respectively) was observed.     

Effects of different cooling techniques on bacterial succession and other spoilage indicators during storage of whole, gutted haddock (Melanogrammus aeglefinus)

Effective cooling of newly caught fish is of great importance to inhibit bacterial growth and therefore increase quality, safety and shelf life of the product. In this study, two commercial cooling media (liquid ice A and B) were tested and their performance was compared to conventional plate ice during chilled 8-day storage of whole, gutted haddock. Temperature was monitored, and deteriorative changes were followed by conventional microbiological counts [(total viable psychrotrophic; specific spoilage organisms and physicochemical methods (pH, TVB-N, TMA, salt content)]. A cultivation-independent method (16S rRNA clone analysis) was used to study the effect of cooling treatments on the bacterial community of haddock initially and at the end of storage. The results show that the bacterial growth behaviour observed for differently cooled fish was not supported by their temperature profiles. Growth of the SSOs, Photobacterium phosphoreum and H₂S-producing bacteria was delayed at early storage, independently of the cooling methods. With further storage, little or no count differences were seen among traditionally iced fish and those cooled in liquid ice with a top ice layer. At the end of storage, significant (p < 0.05) increase in P. phosphoreum and H₂S-producing bacteria counts of skin and flesh sampled from liquid ice with no top ice layer was observed along with higher salt, TVB-N and TMA flesh content. Cultivation-independent analysis confirmed the dominance of P. phosphoreum in fish stored in liquid ice B with no top layer (up to 76% dominance) and liquid ice A with top layer (44% dominance). Psychrobacter and Flavobacterium dominated the microbiota of fish stored in conventional plate ice and liquid ice B with ice top layer. The study shows that the use of liquid ice prepared from brine provides faster initial cooling of whole fish but may create unfavourable conditions under extended storage where the active spoiler P. phosphoreum becomes dominant. Plate ice may therefore be an optimal medium for extended fish storage.     

Volatile chemical and carotenoid profiles in watermelons [Citrullus vulgaris (Thunb.) Schrad (Cucurbitaceae)] with different flesh colors

Twelve watermelon [Citrullus vulgaris (Thunb.) Schrad (Cucurbitaceae)] cultivars with different flesh colors were analyzed by HPLC, GC-FID, and GC-MS for their differences in carotenoid, soluble sugar, organic acid, and flavor. Results showed that all-trans violaxanthin, 9-cis-violaxanthin, and luteoxanthin were the main carotenoid esters in watermelons with yellow flesh. However, watermelons with red flesh were rich in all-trans lycopene and their cis-isomers. High concentrations of β-carotene and pro-lycopenes were found in watermelon with orange-yellow flesh. Large variations in the sucrose concentration were observed among the different watermelons. Sucrose and/or fructose were the dominant sugars, while citric acid and malic acid were the main organic acids in watermelon flesh. Limonene was detected in the watermelon flesh of all investigated genotypes. Interestingly, partial correlation analysis of the chemical concentrations revealed 2 significant (p<0.01) positive correlations between β-ionone and β-carotene, and between (E)-geranyl acetone and prolycopenes.