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.     

Changes in lipids and proteins of marine catfish (Tachysurus dussumieri) during frozen storage

Changes in lipids and protein of marine catfish ( Tachysurus dussumieri ) were followed over a period of 300 days storage at –20°C. Phospholipids decreased and free fatty acids (FFA) and peroxide value (PV) increased. A linear relationship between the decrease in phospholipid and increase in FFA was observed, suggesting that FFA were formed by hydrolysis of phospholipid. Fatty acid analysis showed that polyunsaturated fatty acids (PUFA) increased in the neutral lipid fraction and decreased in the phospholipid fractions; this also suggests hydrolysis of the latter and release of free PUFA into the neutral fraction.
A decrease in water soluble protein (WSP) and salt soluble protein (SSP) indicated denaturation of proteins on prolonged frozen storage; both changes were strongly associated with the changes in peroxide value and free fatty acids.     

CHANGES IN LIPIDS BOUND TO THE I-Z-I FRACTION RELATED TO THE MYOFIBRILLAR FRAGMENTATION INDEX (MFI) OF OVINE LONGISSIMUS DORSI STORED AT 4C

The lipids bound to the I‐Z‐I fraction and the Myofibrillar Fragmentation Index (MFI) of postmortem ovine Longissimus dorsi stored at 4C were investigated. At zero time of storage total lipids were composed of about 50% neutral lipid and 50% phospholipid. During storage, the neutral lipid fraction showed a significant decrease (P < 0,01) in the relative percentage of triglycerides and a significant increase (P < 0.01) in free fatty adds. The composition ofphospholipids extracted from I‐Z‐I with chloroform:methanol 2:1 (v/v) remained unchanged. Further treatment of the I‐Z‐I fraction with chloroform:methanol (2:1, v/v) containing 0.25% (v/v) of concentrated HCl extracted an additional amount of phospholipids. The content of phospholipid extractable from the I‐Z‐I fraction with acidified organic solvents significantly decreased (P < 0.01) during storage and this change was accompanied by a significant increase (P < 0.01) in the MFI.     

CONTRIBUTION OF PHOSPHOLIPIDS TO HEADSPACE VOLATILES DURING STORAGE OF PECANS

The relationship between headspace volatiles and lipid class fatty acid composition was investigated in pecans subjected to room temperature storage for 8 months. During early stages of storage, pentanal predominated in the pecan headspace, whereas at later stages hexanal predominated. Quantities of triacylglycerols recovered from pecans did not change significantly during storage, whereas a decrease in phospholipid content and an increase in free fatty acid content were seen. While losses of polyunsaturated fatty acids (PUFA) in triacylglycerols and free fatty acids only occurred during the last month of storage, PUFA losses were recorded in the phospholipid fraction by 5 months. Based on a strong negative correlation (R =?0.98) between hexanal and its precursor fatty acid (18:2) in phospholipids, the results suggested that membrane lipids would be a primary site of attack during the early stages of oxidation. Future studies with oilseeds, such as pecans, should therefore examine the possibility that variations in phospholipid fatty acid composition could explain cultivar differences in storage stability.     

Fatty acids of a salami-type sausage made of Baltic herring fillets, pork and lard

 The fatty acid composition of "fish wurst", a fermented salami-type sausage made of pork, lard and Baltic herring fillets (Clupea harengus var. membras) was investigated. Changes in the proportions of the 35 most abundant fatty acids were examined throughout the 1-month ripening period followed by a 4-month storage period. The fat composition of the product was stable (32–35%) and retained the characteristics of the main ingredients: oleic acid (37.4%, mean of three production batches) palmitic acid (23.7%) and linoleic acid (10.7%) from lard and fish, stearic acid (11.7%) mainly from lard, and palmitoleic acid (3.0%) and long-chain (C20–C24), polyunsaturated fatty acids (c.a. 6%) mainly from fish. During the 4-week ripening period a statistically significant increase (P≤0.05) was detected in the proportions of minor fatty acids only, i.e. eicosenoic acid (20 : 1n-9), eicosadienoic acid (20 : 2n-6), docosadienoic acid (22 : 2n-6) and docosatrienoic acid (22 : 3n-3). During the 4-month storage of the ripe sausage, the fatty acid composition stabilized. Only the proportion of stearic acid increased significantly during storage, from 11.7% to 12.5%. Received: 23 January 1998 / Revised version: 1 April 1998     

Fatty acids of a salami-type sausage made of Baltic herring fillets, pork and lard

 The fatty acid composition of "fish wurst", a fermented salami-type sausage made of pork, lard and Baltic herring fillets (Clupea harengus var. membras) was investigated. Changes in the proportions of the 35 most abundant fatty acids were examined throughout the 1-month ripening period followed by a 4-month storage period. The fat composition of the product was stable (32–35%) and retained the characteristics of the main ingredients: oleic acid (37.4%, mean of three production batches) palmitic acid (23.7%) and linoleic acid (10.7%) from lard and fish, stearic acid (11.7%) mainly from lard, and palmitoleic acid (3.0%) and long-chain (C20–C24), polyunsaturated fatty acids (c.a. 6%) mainly from fish. During the 4-week ripening period a statistically significant increase (P≤0.05) was detected in the proportions of minor fatty acids only, i.e. eicosenoic acid (20 : 1n-9), eicosadienoic acid (20 : 2n-6), docosadienoic acid (22 : 2n-6) and docosatrienoic acid (22 : 3n-3). During the 4-month storage of the ripe sausage, the fatty acid composition stabilized. Only the proportion of stearic acid increased significantly during storage, from 11.7% to 12.5%. Received: 23 January 1998 / Revised version: 1 April 1998     

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     

Applicability of lactic acid and nisin to improve the microbiological quality of cold-smoked rainbow trout

 The effect of lactic acid and nisin whey permeate on the microbiological and sensory quality of cold-smoked rainbow trout was studied. Lactic acid and whey permeate were mixed with salt solution and injected into fish fillets in concentrations of up to 2.5 g/kg lactic acid, 30 g/kg whey permeate and 20 g/kg sodium chloride. After smoking at 28  °C for 6 h the fillets were sliced, vacuum packed and stored at 3  °C. The aerobic and anaerobic/facultative anaerobic counts were measured after 1, 8, 15, 22 and 29 days of storage. The influence of the treatment on the sensory characteristics was analysed after 8 and 22 days by sensory profiling. A triangle test was used in order to ascertain at which stage the sensory quality of the samples changed during storage. Bacterial counts of smoked fish stored for 29 days were lowest in those samples containing a combination of lactic acid, sodium chloride and nisin whey permeate. Lactic acid alone did not affect the odour or flavour characteristics of the fish but did affect their texture as determined by sensory evaluation making it less elastic when stored at +3  °C for 8 days. A combination of lactic acid and nisin whey permeate enhanced the characteristic fishy flavour of the product. Differences between treatments in elasticity and fishy flavour were not detected after 22 days of storage. According to the triangle test, the samples from all treatments remained unchanged over the first 15 days. Received: 23 March 1998 / Revised version: 19 June 1998     

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.     

Effect of processing and storage on neutral lipids of buffalo meat

Three muscles viz. Triceps brachii (TB), Longissimus dorsi (LD) and Biceps femoris (BF) from different anatomical locations of adult male buffaloes were stored after broiling and pressure cooking under refrigerated (4°C) condition for 3, 6, 9 days and 30, 60, 90 days under frozen (-10°C) storage. At the end of each storage interval they were analysed for total lipids, cholesterol contents and glyceride fractions i.e. monoglycerides (MG), diglycerides (DG), and triglycerides (TG). Muscles differed significantly in total lipids as well as contents of all glyceride fractions. Muscle LD had significantly higher total lipid content than TB and BF. Muscles differed significantly in their esterfied cholesterol (EC) contents. Heat processing increased total lipids, cholesterol, MG, DG and TG contents of all the buffalo muscles studied. Total cholesterol contents remained unchanged during refrigerated and frozen storage. However, EC, MG, DG and TG contents declined during storage. The influence of anatomical locations on fatty acid composition of neutral lipids was observed. The ratio of unsaturated to saturated fatty acids increased due to cooking. A gradual decrease in mono- and polyunsaturated fatty acids was recorded during refrigerated and frozen storage.     

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.     

The evolution of free fatty acids during the ripening of Idiazábal cheese: influence of rennet type

 The object of the present study was to determine the influence of the rennet type on the free fatty acid (FFA) content of Idiazábal cheese. Varying this parameter during cheese-making resulted in significant differences in FFA content in the cheeses during ripening. The main FFAs in both cheese batches were caproic acid (C6 : 0) and capric acid (C10 : 0). The differences between the extreme values for the lipolysis rate were around 45%, which emphasizes the importance of the cheese-making procedure employed on lipolysis in this type of cheese. The use of locally made rennet in the preparation of Idiazábal cheese increased the level of lipolysis in the cheese. Received: 4 December 1998 / Revised version: 18 March 1999     

Lipids classes, fatty acids and carotenes of the leaves of six edible wild plants

 α-Linolenic acid and unusual fatty acids of the ω3 and ω6 series play an important role in the modulation of human metabolism. The presence of these acids in the leaves of several edible wild plants has recently been reported. In this study, six edible wild species were selected in order to establish the fatty acid compositions in their leaf lipids. Thus, young leaves from Amaranthus viridis L.(blet), Chenopodium album L. (goosefoot), Crithmum maritimum L. (rock samphire), Plantago major L. (plantain), Portulaca oleracea L. (purslane) and Verbena officinalis L. (vervain) yielded 1.50, 2.20, 3.02, 1.46, 3.81, and 2.28 g of lipids per 100 g dry plant material. Silica gel chromatography yielded 0.64 g (Plantago major) to 2.19 g (Crithmum maritimum) neutral lipids, 0.37 g (Plantago major) to 1.60 g (Portulaca oleracea) glycolipids, and 0.26 g (Crithmum maritimum) to 0.57 g (Verbena officinalis) phospholipids per 100 g (dry weight). Gas chromatography (GC) showed the major fatty acids to be 18 : 3ω3, 18 : 2ω6 and 16 : 0 in all fractions, with high concentrations of 18 : 3ω3 in the glycolipid fraction. GC-mass spectrometric analyses did not reveal the presence of unusual fatty acids. Carotenes were found in high concentrations, ranging from 30.5 mg/100 g (Chenopodium album) to 89.2 mg/100 g (Portulaca oleracea). The analyzed plants are rich sources of essential fatty acids (18 : 2ω6 and 18 : 3ω3) and also of carotenes. Received: 29 October 1998     

Deterioration of Fresh-Water Whitefish Muscle During Frozen Storage at −10°C

SUMMARY— Organoleptic and chemical deterioration of freshwater whitefish muscle frozen at −10°C for periods up to 16 weeks was assessed. As frozen storage of muscle progressed, the toughness and rancidity of baked muscle increased. The solubility of the myofibrillar protein fraction, "actomyosin," dropped from about 72 to 22% over the 16 week storage period of whitefish muscle. No change in the solubility of sarcoplasmic protein in frozen stored muscle was observed. However, with polyacrylamide disc electrophoresis, two new sarcoplasmic protein bands were detected after 16 weeks of storage. With storage of frozen muscle, water-binding capacity diminished. Although the total lipid and cholesterol contents of muscle remained constant throughout frozen storage, the phospholipid content decreased as the free fatty acid content increased. Oxidative deterioration of lipid in frozen muscle was estimated.     

Hydrolytic changes in the lipids of fish roe products during storage

Lipid hydrolysis and changes in the lipid components during cold and frozen storage of various rainbow trout and whitefish roe products were investigated over a 1-year storage period.
Rainbow trout roe lipids were composed of about 51% phospholipids and 46% triglycerides. The respective percentages in whitefish roe were 31 and 66. During the cold storage of salted roe products both of these lipids were hydrolyzed, the majority of the free fatty acids being produced from triglycerides. Lipid hydrolysis in frozen and pasteurized roe was very slow.
Lecithin as the major phospholipid comprised about 90% and 61% of the total phospholipid in rainbow trout and whitefish roe, respectively. The remainder was composed mainly of cephalin since all the other components amounted to less than 2%. Cephalin was found more susceptible than lecithin to being hydrolyzed although equal or higher amounts of free fatty acids were released in the roe products from lecithin due to its abundance.     

Changes in lipids and their contribution to the taste of migaki-nishin (dried herring fillet) during drying

This study was conducted to investigate the changes in lipids and their effect on the taste of migaki-nishin during drying. Lipid was extracted from herring fillets following different drying stages to measure the degree of lipid oxidation and changes in lipid composition, and fatty acid profile. Peroxide value, carbonyl value and acid value of the lipids were significantly increased (P < 0.05) during the drying period. Marked increase in free fatty acids, with decreases in triglyceride and phospholipid content were observed in proportion to drying time and this result suggested that hydrolysis was induced by lipases and phospholipases. The decreases in polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were observed in the total lipids and phospholipid fraction. In addition, significant increase in PUFAs especially DHA was found in the free fatty acid fraction. Sensory evaluation showed that an addition of DHA to mentsuyu significantly (P < 0.05) enhances the intensities of thickness, mouthfulness and continuity. These results suggest that during drying period lipid oxidation was not only occurred but also lipolysis predominantly released DHA, which might have a contribution to kokumi enhancement of migaki-nishin.     

Lipid Changes in Sea Urchin Gonads during Storage

In lipids of salted sea urchin gonads, the changes in contents of neutral lipids (NL), glycolipids (GL) and phospholipids (PL), in peroxide and carbonyl values, in lipid class compositions of NL and PL, and in fatty acid composition were investigated as a function of storage time. NL increased while GL and PL decreased by autolysis during 180 days storage. The increase of NL resulted from free fatty acids (FFA) [plus fatty acid ethyl esters (FAEE)] generated enzymatically by hydrolysis of PL and GL. Triglycerides were stable throughout a period of storage. In heat-treated and salted gonads, NL, GL and PL remained nearly unchanged during storage, and FFA and FAEE could not be detected. The oxidation of lipids was not detected during 180 days storage, although salted gonads had high content of polyunsaturated fatty acids.     

Changes in lipid composition and fatty acid profile of Nham,a Thai fermented pork sausage,during fermentation

Changes in lipid composition and fatty acid profile of Nham during fermentation were investigated. Total lipids of Nham were in the range 2–3%. The extracted lipid of initial Nham mix consisted mainly of triglycerides (TG), accounting for more than 75% of the total lipid, followed by phospholipids (PL) and a trace amount of diglycerides (DG) and free fatty acid (FFA). During fermentation, TG, DG and PL decreased with a concomitant increase in FFA, indicating lipolysis of Nham lipids during fermentation. Changes in fatty acids of the total lipids, non-polar and polar lipid fractions were observed during fermentation. In both total and non-polar lipid fractions, the major fatty acids found in a descending order were oleic (C18:1), linoleic (C18:2) and palmitic (C16:0) acids, which together accounted for 90% of the total fatty acids. Increases in fatty acid contents in both total and non-polar lipid fractions, were observed with a corresponding decrease in the quantity of fatty acids of phospholipids. As the fermentation proceeded, peroxide value generally increased while TBARS values decreased. Overall, lipid oxidation in Nham occurred during fermentation but did not cause the objectionable odour and taste in any Nham tested.     

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     

Changes in free monosaccharides during storage of some UHT milks: a preliminary study

 Changes in the free monosaccharide fraction and non-casein nitrogen during the 3-month storage of five batches of commercial UHT milk were studied. Batches with high residual proteolytic activity showed a considerable increase in galactose, N–acetyl glucosamine and N–acetyl galactosamine levels during the storage period, whereas their glucose and myo-inositol contents remained unaltered. In batches with slight or negligible proteolytic activity no changes in the free monosaccharide fraction were observed. Received: 1 March 1998 / Revised version: 30 March 1998