Flavors' Decreasing Contribution to p-Anisidine Value over Shelf Life May Invalidate the Current Recommended Protocol for Flavored Fish Oils

The American Oil Chemists' Society (AOCS) Official Method Cd 18–90 for p-Anisidine Value (pAV) is commonly used to evaluate secondary oxidation in fish oils. Flavoring agents in fish oil products may interfere with pAV and lead to inaccurate results. The Global Organization for EPA and DHA (GOED) recommends a protocol for calculating pAV of flavored fish oils based on the assumption that flavors' contribution to the pAV does not change over the course of oxidation. The objective of this study was to test this assumption. All 14 flavors evaluated increased the pAV when added to fresh fish oil; chocolate-vanilla and lemon flavors generated the largest increase. Under accelerated oxidation conditions, both chocolate-vanilla and lemon flavors had a similar effect; oxidized flavored fish oils had lower pAV than oxidized fish oils with newly added flavors. This was due to either an antioxidant effect of the flavor or loss of the flavor during oxidation. Following the GOED recommendation, we would have underestimated the oxidation in the flavored oils. For this reason, the pAV of flavored fish oils should be considered with caution and used in combination with other secondary oxidation markers when possible.     

Effect of ingredients on oxidative stability of fish oil‐enriched drinking yoghurt

The oxidative stabilities of fish oil‐enriched milk and fish oil‐enriched drinking yoghurt were compared by following the development of lipid oxidation in plain milk, plain yoghurt and yoghurt to which ingredients present in drinking yoghurt were added one by one. All samples were enriched with 1 wt‐% fish oil. After 3 weeks of storage, development of peroxide values, volatile secondary oxidation products and fishy off‐flavors were much more pronounced in the milk compared to any of the yoghurt samples, irrespective of any added ingredients used to prepare flavored drinking yoghurt. Thus, pectin, citric acid or glucono‐delta‐lactone did not affect the oxidative stability of fish oil‐enriched yoghurt emulsions. Furthermore, the fruit preparation and added sugar did not lead to increased antioxidative activity. It is concluded that yoghurt as the dairy component in the fish oil‐enriched emulsion was responsible for the remarkably high oxidative stability and was able to protect the n‐3 PUFA against oxidative deterioration. It should be considered that this strong antioxidative effect of yoghurt might mask potential antioxidative effects of the other ingredients in the drinking yoghurt.     

Field studies on chemically mediated behavior in land hermit crabs: Volatile and nonvolatile odors

Land hermit crabs,Coenobita rugosis, were tested in the field in Costa Rica for behavioral responses to odors. Volatile odors associated with horse feces, fruit, and honey attracted crabs within minutes. Odors from dead gastropod flesh were not immediately attractive, but after aging, odors from a variety of flesh sources attracted crabs. Crabs fed actively upon the materials that attracted them. Feeding behavior was stimulated by components of fruit juice and fresh gastropod flesh juices of less than 10,000 daltons, honey, a 0.5 M sucrose solution, and a saturated solution of tyrosine. Twenty additional amino acid solutions tested at 0.1 M concentration were weak feeding stimulants at best. Chemical cues controlled feeding behavior, but not shell acquisition;C. rugosis were not differentially attracted to flesh odors or to living gastropods whose shells they occupied.     

Fish oil sensory properties can be predicted using key oxidative volatiles

The high level of PUFA in fish oil, primarily eicosapentaenoic acid (EPA) and DHA result in rapid oxidation of the oil. Current methods used to assess oxidation have little correlation with sensory properties of fish oils. Here we describe an alternative method using solid phase microextraction (SPME) combined with GC‐MS to monitor volatile oxidation products. Stepwise discriminant function analysis (DFA) was used to classify oils characterized as acceptable or unacceptable based on sensory analysis; a cross‐validated success rate of 100% was achieved with the function. The classification function was also successfully validated with tasted samples that were not used to create the method. A total of 14 variables, primarily aldehydes and ketones, were identified as significant discriminators in the classification function. This method will be useful as a quality control method for fish oil manufacturers. Practical applications: This paper describes an analytical method that can be used by fish oil manufacturers for quality control purposes. Solid phase microextraction and GC‐MS were used to monitor volatile oxidation products in fish oil. These data, combined with results of analyses by a sensory panel, were used to create a function that classified fish oil samples as acceptable or unacceptable. The volatile oxidation products used to in the function were primarily aldehydes and ketones. This method can be used by fish oil manufacturers as an alternative to expensive sensory panels.     

Profiles of volatile compounds in milk containing fish oil analyzed by HS‐SPME‐GC/MS

Long‐chain polyunsaturated fatty acids (LC‐PUFA) have various positive biological effects. Fish oil represents a major source of LC‐PUFA; therefore it is extensively used to enrich food products as, for example, infant formulae, dairy products and fruit juices. However, in the presence of oxygen and metals, LC‐PUFA readily degrade, producing off‐flavors and decreasing the nutritional value of the product. The deterioration of sensory properties (taste and odor) can be easily perceived by the consumer, due to the formation of volatile compounds that are formed by decomposition of lipid hydroperoxides, also known as primary oxidation products. In this study, we used the headspace solid‐phase microextraction‐gas chromatography/mass spectrometry technique (HS‐SPME‐GC/MS) to characterize and quantify volatile compounds in a food matrix supplemented with fish oil. We demonstrated that the HS‐SPME‐GC/MS method is a valuable tool to monitor lipid oxidation at early stages. We identified t‐2‐hexenal and c‐4‐heptenal as possible oxidation markers during the storage of milk enriched with 5% of cod oil.     

Fish meal and oil: Current uses

World landings of fish and shellfish are approaching 100 million metric tons (MMT) annually. Of this total, around 28% is processed into fish meal and oil. Economic pressures due to poor landings, low prices in traditional markets and high fuel costs have forced the industry to seek new markets and products that can take advantage of the unique properties of fish proteins and oils. Fish meal processing continues to evolve. Fresh raw materials and new, low-temperature processing techniques lead to products with excellent nutritional value. These new, special meals are finding uses in feeding farmed fish, early-weaned pigs, ruminants and pets. Fish oils, whether present as fat in the fish meal or as separated oil, are rich in ω3 fatty acids. When fed to food animals, these ω3 fatty acids deposit in the meat and depot fat. Concepts for poultry with an equivalent amount of ω3 fatty acids to lean fish are being developed. Eggs with a high ω3 fatty acid content and good functionality and flavor are under evaluation. Catfish with shelf-stable flavors and high ω3 fatty acids are also under study. ω3 Fatty acids may affect the immune function of livestock. Future research will evaluate the overall immune function of animals, including resistance to disease, survival under stress and hatchability.     

Nutritional consequences of processing soybean oil

A major objective of commercial processing of soybean oil into edible products is to remove unwanted impurities from the oil with the least possible effect on nutritional quality of the oil. Soybean oil is an excellent dietary source of essential linoleic acid and also of tocopherols, which serve as sources of vitamin E and natural antioxidants. The data presented in this report indicate that the nutritional quality of soybean oil is largely retained after typical commercial processing conditions. Hydrogenation does reduce the level of essential fatty acids; however, typical commercial salad and cooking oils and shortenings made from partially hydrogenated soybean oil retain nutritionally significant levels of essential fatty acids. Tocopherols also are present at high levels in the finished oil. Among the unwanted components of crude soybean oil which are effectively removed by processing are pesticide residues, phosphatides, free fatty acids, color pigments, and compounds causing objectionable odors and flavors.     

Effect of dietary fish oil on the rate of very low density lipoprotein triacylglycerol formation and on the metabolism of chylomicrons

The mechanism by which ω3 fatty acids lower plasma triacylglycerol levels was investigated. Rats were fed fish oil, olive oil (10% fat by weight) or a nonpurified diet 4% fat by weight) for 15 days. Lipoprotein lipase was inhibited by intra-arterial administration of Triton WR 1339 to estimate hepatic triacylglycerol output. Rats fed the olive oil diet showed a higher rate of triacylglycerol formation than rats fed the ω3 fatty acid diet or the low-fat diet. All three groups showed identical rates of removal from plasma of intraarterially administered artificial chylomicrons that had simultaneously been labeled with cholesteryl [1-¹⁴C]oleate and [9,10(n)-³H]triolein. Liver radioactivity and total fat content were lowest in rats fed the fish oil diet, indicating that ω3 fatty acids were preferentially metabolized in liver. Chylomicrons obtained from donor rats fed either fish oil containg [¹⁴C]cholesterol or olive oil containing [³H]cholesterol were removed at similar rates when infused together intraarterially into recipient animals. A slower formation of plasma very low density lipoprotein triacylglycerols in rats fed fish oil is probably due to a faster rate of oxidation of the fatty acid chains in the liver resulting in decreased plasma triacylglycerol concentrations.     

Volatile components from tristearin heated in air

Tristearin was heated to 192 C in air, and its volatile oxidation products were collected directly on a cooled (−60 C) gas liquid chromatography column. Subsequently, the volatile products were separated by temperature programing up to 250 C and identified by mass spectrometry. Methyl ketones and aldehydes were the major degradation products along with minor amounts of monobasic acids, n-hydrocarbons, primary alcohols, and γ-lactones. Qualitative results indicated all the fatty acid methylene carbon atoms are susceptible to oxidation. Quantities of aldehydes and ketones were found to be in excess of their taste threshold concentrations, suggesting thermally oxidized saturated fatty acids may be precursors of some odors and flavors associated with heated lipids. Presented at the AOCS Fall Meeting, Philadelphia, September 1974. ARS, USDA.     

Dietary modulation of phospholipid fatty acid composition and lipoxygenase products in mouse lung homogenates

This study investigated the potential of dietary fats to modulate the arachidonic acid content of mouse lung phospholipids and the formation of lipoxygenase products from arachidonic and eicosapentaenoic acids. Prior to breeding, female mice were fed for five months diets with 10 wt% of either olive oil, safflower oil, fish oil, or linseed oil. The same diets were fed to the females during gestation and to the pups from day 18 to day 42 postpartum. On day 42, the phospholipids were extracted from fresh lung tissue and separated into classes [phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylcholine (PC), and phosphatidylinositol (Pl)] by thin-layer chromatography. Methyl esters of phospholipid fatty acids and unesterified fatty acids were analyzed by gas chromatography. At comparable dietary n-3/n-6 ratios, arachidonic acid was reduced 85 and 75% in lungs from mice fed linseed oil and fish oil, respectively, compared to lungs of safflower oil-fed mice. Dietary fats affected the proportion of arachidonic acid in phospholipids in the order: PE>PS>PS>Pl. Following incubation of homogenized lung tissue, the total amount of 12-lipoxygenase products was lowest in lungs from mice fed olive oil, and 12-hydroxyeicosatetraenoic acid was lowest in incubated lungs from mice fed linseed oil. Comparison of the amounts of lipoxygenase substrate fatty acids in the individual phospholipids with the lipoxygenase products suggested that the major substrate pool for the 12-lipoxygenase pathway in mouse lung homogenates was PC.     

Flavor stability of soybean oil. 1. The role of the non-saponifiable fraction

Summary It has been found that the addition of the nonsaponifiable extract of hydrogenated soybean oil to either refined cottonseed oil or refined peanut oil caused these oils to develop odors and flavors characteristic of reverted soybean oil. The non-saponifiable material from linseed oil did not produce a similar effect. When the non-saponifiable extract of hydrogenated soybean oil was added to mineral oil, a sweet, syrupy odor and flavor developed. By selective absorbents it was possible to produce a much greater improvement in hydrogenated than in unhydrogenated soybean oil. These observations are discussed in terms of their relationship to the various theories on the mechanism of reversion.     

Effect of γ-tocopherol on formation of nonvolatile lipid degradation products during frying of potato chips in triolein

Formation of undesirable odors and flavors during food processing operations is an important problem for the food industry. To determine the effect of γ-tocopherol on these negative attributes of fried food, we fried potato chips in triolein with 0, 100, or 400 ppm γ-tocopherol. Triolein extracted from potato chips was sampled for residual γ-tocopherol and nonvolatile degradation products after the chips were aged. RP-HPLC coupled to atmospheric pressure chemical ionization MS and size-exclusion chromatography was used to analyze, samples for degradation products in the triolein absorbed in potato chips as well as the fryer, triolein. MS results showed that γ-tocopherol reduced the production of nonvolatile degradation products in the triolein absorbed by the potato chips and in the triolein in the fryer. Fryer oil samples and extracted potato chip oils with 400 ppm γ-tocopherol had a significantly lower production of degradation compounds than did samples with 100 ppm γ-tocopherol. Both fryer oils and potato chips containing 100 ppm γ-tocopherol had significantly fewer nonvolatile degradation products than did the samples without γ-tocopherol. These nonvolatile compounds are known precursors of negative odors and flavor compounds produced during the frying and aging of foods.     

Monitoring fish oil volatiles to assess the quality of fish oil

The fish oil industry is continuously growing; however there is a lack of analytical methods to assess fish oil quality that correlate with the results obtained through sensory testing. Solid phase microextraction (SPME) provides a means to monitor the concentration of oxidative volatiles in fish oil. Because volatile oxidation products are responsible for the off‐flavours found in oxidized fish oil, this technique may be used as a substitute for sensory panels. Principal component analysis (PCA), combined with sensory panels, can be used to determine the oxidation products that are most correlated with degradation of the sensory properties of the oil. This creates the potential for development of methods that can determine when the sensory qualities of oil have deteriorated beyond an acceptable level.     

Modification of fish oil aroma using a macroalgal lipoxygenase

The odor of fish oil is the major factor limiting its application in food. In this study, the addition of butylated hydroxytoluene to fish oil did not significantly inhibit the generation of fishy and rancid odors. To reduce the undesirable odors, fish oil was treated with lipoxygenase (LOX) to produce volatile compounds via position-specific cleavage of hydroperoxides. An extract of a green marine macroalga, Ulva conglobata, showed a high level of 13-LOX activity and 9-LOX to a lesser extent, and produced strong green, melon-like, and fresh-fish-like flavor notes from fish oil. The LOX-modified fish oil contained 99% of the highly unsaturated fatty acids (HUFA; containing three or more double bonds) originally present, total volatile compounds increased from 3477 to 3787 ppb after LOX treatment. Compounds with strong odors accounted for about 40% of the total volatiles. Increasing the level of LOX activity used to treat fish oil produced higher concentrations of the desirable unsaturated aldehydes, ketones, and alcohols, with odors resembling fresh fish, apple, citrus, melon, fruit, and oyster. These compounds were tentatively identified as E,Z-2,6-nonadienal E-2-hexenal, E,E-2,4-octadienal, E,E-3-5-octadien-2-one, and alcohols E-2-pentenol and 2-butoxyethanol. The LOX treatment also slightly increased the content of the undesirable volatile components, including sour and rancid odors, tentatively identified as acetic acid and E,Z- and E,E-2,4-decadienals     

Behavioral responses ofLittoraria irrorata (SAY) to water-borne odors

Behavioral responses of the gastropod molluscLittoraria (=Littorina)irrorata indicate that it can discriminate among environmental odors. Snails were assayed for responses to 11 odors from plants and animals potentially representing food, shelter, location in the environment, and predators. Crushed conspecifics were included as an alarm odor. Except for odor of crushed conspecifics, all odor sources were water-borne from living intact organisms. Behavioral responses were categorized as no response, positive response, or negative response. For some analyses, negative responses were subdivided into withdrawing and turning responses. Snails responded positively to several plant odors. They did not respond to odors of intact conspecifics, fiddler crabs, or grass shrimp. They responded negatively to odors of a plant found at the upper limit of their minimal habitat, predatory blue crabs, crushed conspecifics, predatory gastropods, and ribbed mussels. Odors of blue crabs on different diets affect the type of negative response the snails display.     

Odor considerations in the use of frying oils

Odors generated into cooking and serving areas during use of oils in pan frying and deep-fat frying are of concern to home and institutional consumers and, in some respects, to industrial users. Odor considerations are factors in the selection of types of oils to be used in both domestic and foreign markets. Comparative techniques have been developed to evaluate room odor characteristics of frying oils. Evaluation research has been done on various oils and cooking fats for room odors developed during frying. Improved odor characteristics contributed by additives to oils have been studied, as well as relationship between the linolenate content of soybean oil and its characteristic room odor. The nature of the volatile constituents which contribute to room odors during frying is the subject of continuing research efforts. Presented at AOCS meeting, St. Louis, Missouri, May 1978.     

Responses of Mud Snails and Periwinkles to Environmental Odors and Disaccharide Mimics of Fish Odor

Estuarine snails, periwinkles (Littoraria irorata), and mud snails (Ilyanassa obsoleta) were tested for behavioral responses to aqueous extracts of tissue macerates, odors of living intact organisms, and to disaccharides derived from heparin. Extracts included salt-marsh cordgrass (Spartina alterniflora), pink shrimp (Penaeus duorarum), crushed periwinkles, and crushed mud snails. Odors included live periwinkles, mud snails, stone crab (Menippe mercenaria), striped hermit crab (Clibanarius vittatus), tulip snail (Fasciolaria hunteria), and mummichog (Fundulus heteroclitus). Responses were determined upon contact by snails of a ring of solution in the bottom of an otherwise dry bowl and by presenting snails in seawater with 25 l of solution on a cotton swab. In each test, the response of 30 individuals was determined. Behaviors were recorded as fed, alarm, and no response. The strongest alarm response (>80% of all snails tested) in both snails was elicited by crushed mud snails. The strongest feeding response was to shrimp and periwinkle extract for mud snails (>70%), and salt-marsh cordgrass extract attracted periwinkles. High percentages of mud snails and periwinkles fled in response to the odors of intact snail predators, stone crabs, tulip snails, and mummichogs. Mud snails and periwinkles did not flee in response to nonpredator odors, including each other's odor, as well as that of hermit crabs, shrimp, and marsh cordgrass. Heparin disaccharides were tested because other studies reported that biological activity of predatory fish odor is due to similar disaccharides originating from fish mucus. Mud snail responses to disaccharides indicate that they respond to the same kinds of molecules as crustacean larvae and that the modified amine on the disaccharide is essential for activity. The Q-tip assay is appropriate for bioassay-directed purification of alarm signals originating in fish body odor.     

Use of soy protein concentrates and lecithin products in diets fed to coho and atlantic salmon

Aquacultural production is increasing in most parts of the world, establishing new and rapidly growing markets for various oil products. One of the more interesting nutritional requirements for aquatic animals is lecithin or phosphatidylcholine. In this paper, lecithin in aquaculture is reviewed with emphasis on freshwater fish and crayfish. Further, new data on use of lecithin and two soy protein concentrates in diets fed to coho and Atlantic salmon are presented. Juvenile coho and Atlantic salmon were fed either solvent-extracted soybean meal (SBM) or Promocalf® at 30% of the diet, Promoveal® at 10, 20 or 30% of the diet, or one of three new lecithin products at a constant level of 3% of the diet. Juvenile coho salmon fed SBM, Promocalf®, or Promoveal® at 30% of the diet exhibited depressed weight gain and an elevated feed conversion ratio (FCR) compared to fish fed a positive control diet. Fish fed 10 or 20% Promoveal® had similar weight gain and FCR compared to fish fed the control diet. Coho salmon fed either of the three lecithin products (Aqualipid®, Blendmax®, or Centrol®) had similar weight gains and FCR values compared to fish fed the control diet. Whole-body proximate components were not as responsive to dietary treatments as weight gain and FCR data. Juvenile Atlantic salmon exhibited depressed weight gain only when fed 30% Promocalf® and all three lecithin products. Further, whole-body crude protein concentrations in fish fed the three lecithin products were depressed.     

Flavor problems of vegetable food proteins

Flavor is a major factor that limits the use of many vegetable proteins in foods. In high quality whole cereal grains, flavor and flavor stability present little or no problem; but when some cereals are further processed into protein concentrates and isolates, objectionable flavors can arise from oxidative deteri-oriation of unsaturated fatty esters in protein-bound lipids. However, degermed wheat and corn flours (endosperm products) have little or no flavor. Raw legumes and oilseeds enriched with respect to lipoxygenases and other metallo-proteins possess lipid-derived, objectionable flavor compounds. Lipoxygenase-mediated conversion of lipids to lipohydroperoxides and their subsequent degradation form volatile and nonvolatile constituents responsible for off-flavors. n-Hexanal, 3-cis-hexenal, n-pentylfuran, 2(1-pentenyl)furan, and ethyl vinyl ketone are major contributors to grassy-beany and green flavors. Higher 2,4-alkadienals have oxidized painty, rancid flavors sometimes noted in residual lipids. Geosmin, an oxygenated hydrocarbon, is responsible for the musty, moldy, earthy flavor of dry beans. This compound may contribute to similar flavors noted in soy and corn protein isolates. Thermally degraded phenolic acids account for some of the objectionable cooked odors of soy products that have been subjected to high temperature treatment such as retorting, autoclaving, and sterilization. Oxidized phosphatidylcholine most likely accounts for the bitter taste of soy products. Oxygenated fatty acids, including the bittertasting trihydroxy octadecenoic acids, have been identified in the bitter phosphatidylcholines isolated from soybeans. Oxidized lipids appear to be associatted with the bitter, astringent, and rancid flavors of protein isolates prepared from wet-milled corn germ flour. Grassy-beany, bitter flavor compounds preexist in the maturing soybean and are also generated during processing. In some legumes development of off-flavors can be readily controlled by rapid inactivation of lipoxygenase with heat, alcohol, or acid treatment. Legume powders of acceptable flavor quality can be prepared by wet-milling whole seeds in aqueous alcohols. Extraction of meals with hydrogen bond-breaking solvents, such as alcohols or azeotropic mixtures of hexane and alcohol, effectively removes protein-bound lipids to yield concentrates with greatly improved flavors. Soy protein concentrates approaching the blandness of wheat flour have been prepared by a combination of azeotrope extraction and steaming. Similar processes can also be used to greatly improve flavor scores of corn germ protein isolates. Based on our present knowledge about the identity of off-flavor constituents and how they are derived, much progress has been made to effectively remove or modify them. These developments should result in new emerging technology that would be applicable to the manufacture of highly acceptable protein products from various vegetable sources.     

Pollution control in the fatty acid industry

Operations of the fatty acid industry create waste-waters, emissions to the air, and solid wastes which have the potential of insulting the quality of the environment in a number of wasy. Some of the controversy and the problems that are current in the national environmental effort are discussed. As to the fatty acid industry prospects, some attention may come to the industry if toxics are found to be in the industry’s wastewaters. New air emissions permit will be difficult if not impossible to obtain. Long delays and expensive data gathering will be involved. Disposal of solid waste classified as hazardous materials will become extremely costly and involve much paperwork. Wastewaters can originate from any of the process steps: spills and tank bottoms from receiving and storage, foots from alkaline extraction pretreatment, condensate from pressure reduction after fat splitting, condensing water and condensate from fatty acid distillation, and condensing water from glycerine evaporation and distillation. The organic matter in the wastes is biologically degradable so one pollutional effect is reduction of the oxygen level in receiving streams. Oil not in soluble or finely dispersed state is objectionable for the additional reason that it forms slicks or films in the water surface. Fatty acids in soluble forms are toxic to fish in fairly low concentrations. Heavy metal catalysts used for fat splitting or hydrogenation such as zinc are objectionable at trace levels. Source control methods include good operator attention to minimize avoidable losses, optimum recovery of fatty acids and oil in recovery steps, mist eliminators and entrainment separators in distillation and evaporator vapor conduits, and use of indirect condensers in place of direct spray condensers. Treatment of wastewaters includes removal of floatable fat and fatty acids by gravity settling. The residual wastewaters so pretreated are susceptible to treatment processes using bacteria for their degradation. Most fatty acid producers discharge the wastewater to municipal systems in which they receive biological treatment along with residential sewage. Air emissions are minimal for the standard criteria of particulates, organics, etc., because of the low vapor pressure of the materials involved. Odor is not subject to federal legislation, and local regulations and circumstances of concern vary. Odors originate from storage tank vents, from noncondensables vented to the atmosphere from condensers on pressure-relief operations, and from stills. Cooling tower recirculating systems may release odors condensed in the condensing sprays, or odors may be generated from bacteria growth in the system. Odors are controlled by wet scrubbers on off gases and by conveying the gases (air) to the boiler as air supply. This practice incinerates the odor-producing compounds. Solid wastes include spent clay used in pretreatment and foots from glycerine stills. Deposit in sanitary landfills is the usual disposal. If solid wastes contain much metal catalysts, their disposal must be to special sites approved for hazardous waste materials.