Differential lipid damage in various muscle zones of frozen hake (Merluccius merluccius)

 A comparison of the lipid damage produced in different hake zones was carried out during frozen storage at –11 and –18  °C. Three light muscle zones and the dark muscle were considered. Lipid oxidation [conjugated dienes; thiobarbituric acid index (TBA-i); fluorescence formation] and hydrolysis (free fatty acids, FFA) were determined. The most predominant lipid damage in all zones was hydrolysis, at the end of storage reaching values of about 40% (for the light muscle zones) and 12% (for the dark muscle) of the total lipids at –11  °C. Significant (P<0.05) correlation value (r=0.67–0.85) relationships between the frozen storage time and the FFA content were obtained for the four muscle zones at both temperatures. A comparison of the regression lines slopes in the different zones showed that a lower (P<0.05) lipolitic activity was produced in the dark muscle compared to the three light zones at both temperatures. A low lipid oxidation development was produced in the three light muscle parts, so that no significant differences between them could be assessed. However, the dark muscle showed a higher oxidation development (TBA-i and fluorescence formation) as a result of a higher lipid content and the presence of prooxidant constituents. Received: 16 June 1998     

Effect of previous gutting on rancidity development in horse mackerel (Trachurus trachurus) during frozen storage at −20 °C

Gutting was applied to fresh horse mackerel (Trachurus trachurus) to study its effect on rancidity development during a prolonged frozen storage (up to 12 months at −20°C). To do so, chemical (free fatty acids, FFA; peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescence ratio, FR) and sensory (odour and taste) analyses were carried out. The results showed that the gutting of horse mackerel led to a higher degree of oxidation in the frozen product, according to the chemical (PV, TBA-i and FR) and sensory (odour and taste) analyses. However, a lower extent of lipid hydrolysis (FFA formation) was detected at the end of the storage (twelfth month) as a result of gutting. It is concluded that the gutting of a medium-fat fish species such as horse mackerel is not recommended as previous treatment to frozen storage.     

Influence of storage time and temperature on lipid deterioration during cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) frozen storage

Lean fish deterioration during frozen storage (−30 and −10 °C) for up to 1 year was studied by the assessment of lipid changes. Comparison between a formaldehyde (FA)-forming species (cod) and a non-FA-forming one (haddock) was carried out. Lipid damages were measured on the basis of free fatty acids (FFA), peroxide value (PV), thiobarbituric acid index (TBA-i) and fluorescent compounds. In both species at −30 °C, most lipid damage indices showed significant correlations with the storage time. However, at −10 °C, only the FFA and fluorescence detections provided significant correlations with the storage time. Comparison between the fish species showed higher lipid oxidation (PV and TBA-i) and hydrolysis (FFA content) in haddock than in cod at −10 °C; however, a higher fluorescence development was observed in cod at the same temperature. At −30 °C, little differences in lipid damage indices were detected between the two species. © 1999 Society of Chemical Industry     

Effect of brine pre-treatment on lipid stability of frozen horse mackerel (<Emphasis Type="Italic">Trachurus trachurus</Emphasis>)

The rancidity development during the frozen storage (-20 °C) of an under-utilised medium-fat fish species (horse mackerel; Trachurus trachurus) was investigated. Special attention was given to a pre-freezing treatment consisting of an immersion in NaCl solution (5%, 10%, and 20%) and its effect on lipid damage during the fish frozen storage. Lipid hydrolysis (free fatty acid content) and oxidation (conjugated dienes formation; peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescence formation, FR) were studied up to 270 days of frozen storage. Oxidative rancidity measured by the PV, TBA-i, and FR showed an increase with the frozen storage time and also as a result of an increasing salt content in fish muscle. A high peroxide formation was observed at day 210 of frozen storage, especially in the case of 20% NaCl treated samples. Lipid hydrolysis also increased with the frozen storage time; at the end of the experiment (270 days), a decreasing effect of muscle salt content on lipid hydrolysis was observed. Employment of appropriate antioxidant additions is recommended if salting pre-treatment is to be needed to avoid a large lipid oxidation development and ensure a longer shelf-life time.     

Lipid Hydrolysis and Oxidation Related to Astaxanthin Content in Light and Dark Muscle of Frozen Stored Rainbow Trout (Oncorbynchus mykiss)

Astaxanthin decreased significantly during frozen storage in both light and dark muscle of farmed rainbow trout (Oncorhynchus mykiss). Astaxanthin sunolementation did not affect lipid hydrolysis and oxidation during frozen storage of fish muscle. Deposition of astaxanthin was higher in dark muscle than in light muscle. Astaxanthin decreased in both supplemented and nonsupplemented fish. The sum of trans-astaxanthin and its cis-isomers decreased during frozen storage, indicating mechanisms other than trans-cis isomerization were causes. α-Tocopherol decreased to the same extent in both light and dark muscle for both diets.     

Effect of dietary levels of fat, α-tocopherol and astaxanthin on colour and lipid oxidation during storage of frozen rainbow trout (Oncorhynchus mykiss) and during chill storage of smoked trout

 Female rainbow trout (Oncorhynchus mykiss) with an initial weight of 0.8–0.9 kg were raised in two experiments including a total of 2550 fish divided into 17 groups. The fish were raised for 6 months on 13 different feeds (four fish groups were replicates) varying in dietary levels of fat (27% or 32%), astaxanthin (40, 70 or 100 mg astaxanthin/kg feed) and vitamin E (α-tocopherol; 100, 300 or 600 mg all-rac-α-tocopheryl acetate/kg feed). The levels of fat, astaxanthin and α-tocopherol in the fillets all increased with increasing dietary levels of each feed component. Furthermore, astaxanthin deposition was found to be significantly improved by increasing the dietary fat level from 27% to 32%, but was not affected by dietary levels of α-tocopherol. The highest deposition of α-tocopherol was found in fish fed the lowest level of astaxanthin (40 mg/kg), whereas α-tocopherol deposition was unaffected by the dietary fat level. Frozen storage (–28  °C) of gutted, cleaned and glazed raw fish for 18 months significantly reduced astaxanthin and α-tocopherol levels, while lipid oxidation, measured as thiobarbituric acid reactive substances (TBARS) was limited. In the first experiment, the highest TBARS levels were found during frozen storage in fish fed the lowest level of astaxanthin (40 mg/kg versus 70 mg/kg or 100 mg/kg); unaffected by dietary levels of α-tocopherol (100 mg/kg versus 600 mg/kg), whereas the dietary astaxanthin level (70 mg/kg versus 100 mg/kg) did not influence lipid oxidation in frozen fish in the second experiment. After brine injection, fillets of fish were smoked and a vacuum-packed (95%), sliced product in a transparent laminate was produced. The quality (pigmentation and lipid oxidation) during 3 weeks of illuminated, chill storage (3  °C) was compared for smoked products produced from fresh fish and from fish stored at –28  °C for 12 months and 18 months. Smoked fillets from fish fed 32% fat were found to be less red than those from fish fed 27% fat, and the astaxanthin content and surface redness of the smoked product decreased during chill storage. Lipid oxidation was pronounced in smoked trout, but a high level of α-tocopherol in the fillet significantly reduced lipid oxidation during chill storage of the smoked product. Lipid oxidation in smoked fillets from fish fed 32% fat was more pronounced than in fish fed 27% fat, but increasing the dietary α-tocopherol level from 300 mg/kg feed to 600 mg/kg feed effectively counteracted the negative effect of the high-fat diet on lipid oxidation in the smoked product. Astaxanthin did not affect lipid oxidation in the chill-stored smoked product, in contrast to the frozen, raw fish. Astaxanthin seems to protect against the very early stages of lipid oxidation, while α-tocopherol is more important as an antioxidant at more advanced stages of lipid oxidation. Received: 8 January 1998 / Revised version: 23 March 1998     

Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged. Received: 16 March 1998 / Revised version: 17 June 1998     

Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged.     

Lipid oxidation in high-pressure processed chicken breast muscle during chill storage: critical working pressure in relation to oxidation mechanism

 The oxidative stability of chicken breast muscle subjected to high-pressure treatment at 300, 400, 500, 600, 700 or 800 MPa for 5 min or 10 min, or to heat treatment (80  °C for 10 min) and subsequent storage at 5  °C was evaluated over a 2-week period. Lipid oxidation in pressure-treated chicken breast muscle monitored as formation of thiobarbituric acid reactive substances depended to a high degree on the working pressure and less on the pressurizing time. The pressure treatment at 800 MPa for 10 min was found to enhance lipid oxidation to the same extent as the heat treatment. Pressure treatment at 600 MPa and 700 MPa resulted in less oxidation. Chicken breast muscle exposed to pressure at or below 500 MPa showed no indication of rancidity, similar to what was found for untreated meat during chill storage; accordingly 500 MPa is a critical pressure for pressure treatment of chicken breast muscle. Analysis of non-heme iron in pressure-treated chicken breast muscle revealed that the notable increase in lipid oxidation caused by high pressure above 500 MPa did not result from the release of iron ions during high-pressure treatment. Furthermore, no influence of high-pressure treatment on the catalytic activity of metmyoglobin on lipid oxidation was observed in a model system, and it is concluded that increased lipid oxidation is probably related to membrane damage. Received: 23 August 1999     

Use of β-hydroxyacyl-CoA-dehydrogenase (HADH) activity to differentiate frozen from unfrozen fish and shellfish

 Further work on an enzymic method to differentiate frozen from unfrozen fish and shellfish is reported. The method is based on the release of the β-hydroxyacyl-CoA-dehydrogenase (HADH) from mitochondria during freezing. Enzymic activity was evaluated in fresh and frozen thawed samples from sole (Solea solea), sea bream (Pagellus centrodontus), hake (Merluccius merluccius), gilt headed bream (Sparus aurata), sea bass (Dicentrarchus labrax), salmon (Salmo salar), prawn (Penaeus japonicus) and Norwegian lobster (Nephrops norvegicus). Changes in the HADH activity of fresh and frozen thawed samples were compared after freezing at –196  °C for 15 min. Two values were obtained: U (by dividing: HADH activity of samples frozen at –196  °C, then thawed/HADH activity of unfrozen samples) and F (by dividing: HADH activity of samples frozen at –18  °C, thawed, then frozen at –196  °C /HADH activity of samples frozen at –18  °C, then thawed). Statistical analysis showed significant differences (P≤0.05) between both quotients for gilt headed bream, salmon, sea bream, sole and prawn, and an arbitrary limit was set at 2 to differentiate frozen thawed from unfrozen samples. The application of this limit made it possible to discriminate the unfrozen from the frozen thawed state of around 90% of the total samples analysed. Best results were obtained for prawn (100% of samples differentiated). In the present paper, a laboratory routine is proposed based on the comparison of the HADH activity of a sample analysed straight away and that of a sample frozen at –196  °C and then thawed. The reported method is simple and fast. The entire laboratory procedure can be performed in 45 min. Received: 20 July 1998 / Revised version: 2 November 1998     

Kinetics of softening of potato tissue by temperature fluctuations in frozen storage

 Pre-packed and unpacked potato tissues were frozen, subjected to temperature fluctuations and then thawed. Temperature fluctuations ranged from –24  °C to –18  °C and from –18  °C to –6  °C. The number of fluctuacions ranged from 0 (that is to say, only freezing and thawing processes) to 32 at each above fluctuation range, simulating practical frozen storage conditions. Compression, shear and tension tests were carried out to measure the extent of structural damage caused to the potato tissue. Plots of log (rheological parameters and moisture content) versus number of temperature fluctuations showed two distinct regions; the first was a rectilinear plot with a steep negative slope up to four fluctuations. The second was also a rectilinear plot with a shallow negative slope beyond four fluctuations. For higher number of fluctuations, most of rheological parameters reached a value almost constant. These two-stage softening rate curves are consistent with the biphasic model and qualitatively similar to those for thermal softening of the vegetables. This study shows that two substrates S_a and S_b may be involved in providing firmness to potato tissue in freezing and frozen storage conditions. By analogy with earlier works, the term "frozen storage firmness" can be proposed to describe the amount of firmness that is resistant to degradation by freezing with temperature fluctuations during frozen storage and final thawing of the product. Received: 30 April 1999     

Effect of a Polyphenol–Vacuum Packaging on Lipid Deterioration During an 18-Month Frozen Storage of Coho Salmon (<Emphasis Type="Italic">Oncorhynchus kisutch</Emphasis>)

A packaging system combining a polyphenol-rich film and vacuum (PPRF–VP) was applied to farmed coho salmon (Oncorhynchus kisutch) muscle for an 18-month storage (−18 °C). For it, two different concentrations of polyphenol compounds (namely, p-coumaric and ferulic acids) obtained from a barley husk extract were applied (PPRF–VP conditions) and compared to vacuum packaging without polyphenol presence (vacuum control; VP condition) and to packaging in the absence of vacuum and polyphenols (control; CP condition). The study was addressed to lipid hydrolysis and oxidation development and to lipid changes related to nutritional value. Both PPRF–VP conditions provided an inhibitory effect (p < 0.05) on conjugated diene and fluorescent compound formation in frozen salmon. Compared to CP condition, vacuum packaging (PPRF–VP and VP conditions) led to lower (p < 0.05) peroxide and anisidine values and to an inhibitory effect (p < 0.05) on α- and γ-tocopherol losses. No effect (p > 0.05) of polyphenol presence and vacuum packaging could be inferred on free fatty acid formation (hydrolysis development) and on polyunsaturated fatty acid retention (polyene index assessment). A low rancid odour development was observed in all kinds of fish samples, this being lower (p < 0.05) in fish kept under vacuum (PPRF–VP and VP) conditions.     

Principal component analysis to study the effect of temperature fluctuations during storage of frozen potato

 The effects of temperature fluctuation ranges, number of fluctuations carried out, and packaging during frozen storage on the texture of potato tissue in terms of compression, shear, and tension rheological parameters were assessed through data generated according to a factorial design using principal component analysis (PCA). Five ranges of fluctuation (–24  °C to –18  °C, –18  °C to –12  °C, –12  °C to –6  °C, –24  °C to –12  °C and –18  °C to –6  °C) applied 2, 4, 8, 16, 24, and up to 32 times on unpacked and pre-packed frozen potatoes, were considered. The controls were unpacked and prepacked frozen tissues thawed immediately without undergoing any fluctuation. In addition, several geometrical, technological, and chemical parameters were determined. PCA showed that maximum shear force, F_s was the best rheological parameter for differentiation of the structural damage and softening occurring in the tissue at each treatment, which was closely related to its duration, TT _d . PCA did not permit complete discrimination between the five fluctuation ranges, but it clearly separated samples subjected to –18  °C/–6   °C from those subjected to –24  °C/–18  °C. Frozen samples undergoing up to four fluctuations formed a separate cluster from those undergoing a higher number. Analysis also clearly separated unpacked from pre-packed samples in response to slower freezing rates reached in the latter. Received: 17 December 1999     

Characteristics of Mackerel Mince Lipid Hydrolysis

The lipid hydrolysis products in minced mackerel stored under vacuum at 2–3°C for 15 days were free fatty acids (FFA) and 1,2-diglycerides (DG); no 1,3-DG br monoglycerides were obsrved, Lysophosphati-dylcholine fLPC and lvsoohosohatidvlethanolamine (LPE) increased and then ddcreased with time: Lysiphosphatidylserie was not observed. More FFA, 1,2-DG, LPC, and LPE were detected in dark muscle than in light muscle. The initial fatty acid composition, by GC, showed no significant differences (α-0.05) among whole, light and dark muscles. When the lipid extracts were separated into three fractions (1: mostly triglycerides; 2: mostly FFA, DG, and cholesterol; and 3: mostly phospholipid), the degree of unsaturation of the lipids in fraction 2 was between those in fraction 1 and 3 and increased with time. These findings support the possibility that fish lipid hydrolysis may affect fish wholesomeness.     

Hydrolysis and oxidation of European eel oil during frozen storage for 48 weeks

The quality assessment of the wild European eel (Anguilla anguilla) stored at −20 °C was assessed by sensory, chemical (total volatile basic nitrogen (TVB-N), peroxide value (PV), free fatty acid (FFA), thiobarbituric values (TBA) and pH) methods. The sensory analysis of showed that European eels were acceptable by panellists and can be stored for more than 48 weeks at −20 °C. No effects of frozen storage were observed on the proximate composition of eel. The level of TVB-N showed fluctuations (7.09–14.72 mg TVB-N/100 g) during frozen storage period, thus TVB-N could not be used as an indicator of frozen eel quality. FFA, PV and TBA values showed fluctuations during frozen storage period but remained low at the end of storage period, PV reached to the maximum level of 13.20±1.73 meq/kg, which did not exceed the maximum recommended value for human consumption (20 meq/kg). The release of FFA slightly increased (P>0.05) from the initial value of 0.88 to 2.14 (expressed as % of oleic acid) until 32 weeks of frozen storage while TBA increased from the initial value of 0.085 mg MA/kg to maximum level of 0.7696 mg MA/kg after week 40. After that, their values decreased to 1.82 and 0.5577 at week 48, respectively. This study showed that off-flavour and off-odour was not detected and frozen European eels were still acceptable by panellists and can be stored for more than 48 weeks at −20 °C.     

Effect of essential oils treatment on the frozen storage stability of chub mackerel fillets

The effect of bay leaf (BLO), thyme (TO), rosemary (RO), black seed (BSO), sage (SO), grape seed (GSO), flaxseed (FSO) and lemon (LO) essential oil from vegetable extracted on lipid oxidation and some other quality parameter of frozen chub mackerel during frozen storage at −20°C were examined over a period of 11 months. Taste, odour, texture and overall acceptability of control samples were given ‘unacceptable’ scores by the sixth month. Based primarily on sensory data, the shelf-lives of frozen chub mackerel were found 6 month for samples treated with oil of TO, RO, BSO, SO and LO and 7 month for samples treated with BLO, GSO and FSO. During the 11-months storing process of chub mackerel, the values of pH, total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N) both in control group samples and samples treated with oils did not reach to deterioration levels. Thiobarbitüric acid (TBA) and free fatty acid (FFA) values for all treatments remained lower than TBA and FFA values of control samples throughout the 11 month storage period. Particularly, thyme oil treatment is effective in delaying lipid oxidation. Bay leaf, rosemary, sage, lemon, flaxseed and grape seed oils were fallowed.     

Freeze- and bake-stable glazing for confectionery products characterized by differential scanning calorimetry

 A freeze- and bake-stable glazing for pastry has been developed based on an optimization procedure in which starches and carrageenans as thickening agents were combined with sugar alcohols and sodium tripolyphosphate. Instrumental gloss measurement on test biscuits showed that glazing consisting of 3% ι-carrageenan and 15% sorbitol (w/w) had maximal gloss. This was confirmed on pastry products. In contrast to glazing based on mannitol, no crystallization problems were encountered for this glazing, for which differential scanning calorimetry showed that some water freezes at –3  °C followed by freezing of supercooled encapsulated water at –20  °C and by a glass transition at –61  °C. During normal frozen storage of preglazed, nonbaked pastry, the glazing is thus in a nonstable rubbery state with a limited resistance to water migration and ice crystal formation, which can be substantially improved by storage at temperatures below –61  °C. Received: 1 March 1999 / Revised version: 19 April 1999     

Lipid damage during frozen storage of Atlantic halibut (Hippoglossus hippoglossus) in active packaging film containing antioxidants

The use of peroxide value (PV), free fatty acids (FFA), thiobarbituric acid reactive substances (TBARS) and p-anisidine value (PA) proved suitable for studying lipid hydrolysis and primary and secondary lipid oxidation in samples of Atlantic halibut throughout frozen storage. After twelve months, the FFA values in the samples packaged with the film containing natural antioxidants (extracted from barley husks) were similar to the FFA value in the control sample after 9 months. Maximum peroxide value in the samples packaged with the antioxidant-containing film was found one month after the maximum value observed in the control sample. After six months, the concentration of malondialdehyde in the control sample was approximately 30–50% higher than in samples packaged in film containing antioxidants. The results confirm the efficacy of natural antioxidants derived from barley husks and antioxidant active packaging film in slowing down lipid hydrolysis and increasing the oxidative stability of Atlantic halibut flesh.     

Discoloration and lipid deterioration of farmed giant catfish (Pangasianodon gigas) muscle during refrigerated storage

ABSTRACT:  Discoloration and lipid deterioration of farmed giant catfish ( Pangasianodon gigas) muscle during 14 d refrigerated storage were investigated. Lipid deterioration, lipolysis, and lipid oxidation in both dorsal and ventral muscles increased as storage time increased. A progressive formation of primary lipid oxidation products monitored by the increase in conjugated dienes (CD) was observed ( P < 0.05) and the increase in thiobarbituric reactive substances (TBARS), an index of secondary lipid oxidation products, was noticeable throughout the storage ( P < 0.05). The pH of both dorsal and ventral muscles tended to increase as storage time continued ( P < 0.05). A gradual increase in free fatty acid (FFA) formation was found within the first 10 d of refrigerated storage ( P < 0.05), suggesting hydrolysis induced by lipases and phospholipases. However, a sharp decrease in FFA content was observed at the end of storage. Refrigerated storage also resulted in changes in redness index of both dorsal and ventral muscles. These changes were coincidental with the changes in metmyoglobin content. Therefore, the discoloration and lipid changes in giant catfish muscle during refrigerated storage depended on the muscle type and might be related to the difference in composition between dorsal and ventral muscles.