Flavor Reversion Research Articles

Mutations in the genes responsible for the synthesis of furan fatty acids resolve the light-induced off-odor in soybean oil.

Soybean oil is the second most produced edible vegetable oil and is used for many edible and industrial materials. Unfortunately, it has the disadvantage of 'reversion flavor' under photooxidative conditions, which produces an off-odor and decreases the quality of edible oil. Reversion flavor and off-odor are caused by minor fatty acids in the triacylglycerol of soybean oil known as furan fatty acids, which produce 3-methyl-2,4-nonanedione (3-MND) upon photooxidation. As a solution to this problem, a reduction in furan fatty acids leads to a decrease in 3-MND, resulting in a reduction in the off-odor induced by light exposure. However, there are no reports on the genes related to the biosynthesis of furan fatty acids in soybean oil. In this study, four mutant lines showing low or no furan fatty acid levels in soybean seeds were isolated from a soybean mutant library. Positional cloning experiments and homology search analysis identified two genes responsible for furan fatty acid biosynthesis in soybean: Glyma.20G201400 and Glyma.04G054100. Ectopic expression of both genes produced furan fatty acids in transgenic soybean hairy roots. The structure of these genes is different from that of the furan fatty acid biosynthetic genes in photosynthetic bacteria. Homologs of these two group of genes are widely conserved in the plant kingdom. The purified oil from the furan fatty acid mutant lines had lower amounts of 3-MND and reduced off-odor after light exposure, compared with oil from the wild-type.

Design of high-monounsaturated fatty acid soybean seed oil using GmPDCTs knockout via a CRISPR-Cas9 system.

Design of high-monounsaturated fatty acid soybean seed oil using GmPDCTs knockout via a CRISPR-Cas9 system.

Metabolic engineering of cottonseed oil biosynthesis pathway via RNA interference.

Cottonseed oil is recognized as an important oil in food industry for its unique characters: low flavor reversion and the high level of antioxidants (VitaminE) as well as unsaturated fatty acid. However, the cottonseed oil content of cultivated cotton (Gossypium hirsutum) is only around 20%. In this study, we modified the accumulation of oils by the down-regulation of phosphoenolpyruvate carboxylase 1 (GhPEPC1) via RNA interference in transgenic cotton plants. The qRT-PCR and enzyme activity assay revealed that the transcription and expression of GhPEPC1 was dramatically down-regulated in transgenic lines. Consequently, the cottonseed oil content in several transgenic lines showed a significant (P < 0.01) increase (up to 16.7%) without obvious phenotypic changes under filed condition when compared to the control plants. In order to elucidate the molecular mechanism of GhPEPC1 in the regulation of seed oil content, we quantified the expression of the carbon metabolism related genes of transgenic GhPEPC1 RNAi lines by transcriptome analysis. This analysis revealed the decrease of GhPEPC1 expression led to the increase expression of triacylglycerol biosynthesis-related genes, which eventually contributed to the lipid biosynthesis in cotton. This result provides a valuable information for cottonseed oil biosynthesis pathway and shows the potential of creating high cottonseed oil germplasm by RNAi strategy for cotton breeding.

Analysis of volatile compounds from chlorophyll photosensitized linoleic acid by headspace solid-phase microextraction (HS-SPME)

Volatile compounds from linoleic acid with or without added 5 ppm chlorophyll under light and in the dark were studied by headspace-solid phase microextraction (HS-SPME)-gas chromatography (GC)-mass spectrometry (MS). Coefficient of variation (R2) for the total peak areas by HS-SPME was 1.8%. Total volatiles (TI) in linoleic acid without added chlorophyll under light and in the dark were not significantly different for 48 hr at 4°C (p>0.05). TI in linoleic acid with 5 ppm chlorophyll under light at 4°C for 0, 6, 12, 24, and 48 hr increased from 8.9 to 11.6, 21.7, 26.1, and 29.3 (1×104) in electronic counts, respectively. 2-Pentylfuran, an undesirable reversion flavor compound in soybean oil, trans-2-heptenal, and 1-octen-3-ol were formed and increased only in chlorophyll photosensitized samples. Chlorophyll can generate singlet oxygen from triplet oxygen upon the exposure of fluorescent light, which plays important roles in the formation of 2-pentylfuran, trans-2-heptenal, and 1-octen-3-ol in linoleic acid.

Thanks to literature and fellow scientists

Formal training has the disadvantage that trainees may simply accept what they are taught without questioning it, unlike the autodidact who can only learn by asking questions all the time. Sometimes, he will not get an answer and that need not be because the question is stupid, but may be because his peers are used to there being no satisfactory answer and have simply accepted the conventional mythology without further question. So it is about time to ask some assorted questions and where possible, suggest how to find an answer: 1) Why does the composition of the solvent used to extract oil from oilseeds affect the amount of oil being extracted and its phosphatide content? 2) Why does a heat treatment (Alcon, Exergy, expander) increase the phosphatide content of the crude oil and decrease its non-hydratable phosphatide (NHP) content? 3) Why does water degumming of crude oil remove relatively more magnesium than calcium? 4) What is the mechanism of phosphatide removal by silica hydrogel and why is it enhanced by simultaneous soap removal? 5) What is the mechanism of NHP-removal during alkali neutralisation? 6) Could it be that the Long Mix neutralisation process as used in the US leads to insufficient removal of the pro-oxidants copper and iron and that this explains why oil tends to less stable in the US than in Europe, especially when it contains linolenic acid? 7) Could different deodorisation conditions explain this geographically determined anomaly? 8) What happens during flavour reversion? 9) Why is walnut oil more stable in the nut than in the bottle? 10) How much oil is lost by saponification or hydrolysis during refining? 11) What is the mechanism of colour fixation? 12) Does the activity of interesterification catalysts depend on their counter cation? 13) What is the chemical nature of the colour formed on interesterification catalyst activation? 14) What is crystal memory? Does it exist? However, we should not forget the Dutch proverb that: “One fool can ask more questions than ten wise men can answer.” On the other hand, exposing myths is half the fun and asking the right question often provides half the answer.

Singlet Oxygen Oxidation for 2‐Pentylfuran and 2‐Pentenyfuran Formation in Soybean Oil

ABSTRACT: 2‐Pentylfuran and isomers of 2‐pentenylfuran are known to be mainly responsible for the undesirable reversion flavor of soybean oil. Solid‐phase microextraction ‐ gas chromatography ‐ mass spectrometry was used to isolate, separate, and identify 2‐pentylfuran and isomers of 2‐pentenylfuran from soybean oil containing 5 ppm chlorophyll in a gas‐tight sample bottle during oxidation under light. Both 2‐pentylfuran and isomers of 2‐pentenylfuran increase as light exposure time and added chlorophyll increased. The compounds were neither formed in the oil containing 5 ppm chlorophyll under dark nor in the chlorophyll‐free soybean oil under light. The singlet oxygen oxidation mechanism for the formation of 2‐pentylfuran from linoleic acid and isomers of 2‐pentenylfuran from linolenic acid are proposed. Removal of chlorophyll will reduce reversion flavor formation.

Chemistry and Reaction of Singlet Oxygen in Foods.

Singlet oxygen is a highly reactive, electrophilic, and nonradical molecule. It is different from diradical triplet oxygen in its electron arrangement. Photosensitizers can form singlet oxygen from triplet oxygen in the presence of light. The reaction rate of singlet oxygen with foods is much greater than that of triplet oxygen due to the low activation energy. Singlet oxygen oxidation produces undesirable compounds in foods during processing and storage. However, carotenoids and tocopherols in foods can minimize singlet oxygen oxidation. The in-depth scientific knowledge on the formation, reactions, quenching mechanisms, and kinetics of singlet oxygen can greatly improve the quality of foods by minimizing the oxidation during processing and storage. The single oxygen oxidation of foods has contributed to the explanation of several important chemical reactions in the reversion flavor in soybean oil, sunlight flavor in milk products, and the rapid losses of vitamin D, riboflavin, and ascorbic acid in milk under light storage.

Processing of Oilseeds and Oils

Various steps in the processing of soybean and canola into finished oil and meal products are reviewed. The presence of nonhydratable phospholipids (NHP) in crude oil reduces the efficiency of degumming and makes necessary additional acid treatment, with consequent loss of neutral oil. Recent heat treatment of seeds or flakes before extraction using ALCON, Expander or Super Expro is explained in detail. Enzymatic degumming and spent clay disposal are briefly explained. Topics on flavor reversion of edible soybean oil are introduced.

The impact of furanoid fatty acids and 3‐methylnonane‐2,4‐dione on the flavor of oxidized soybean oil

AbstractOils from soybeans with high or low contents of furanoid fatty acids were evaluated during storage for flavor intensity of soybean oil (SBO) off‐flavor, but no significant differences were found. In addition, the compound 3‐methylnonane‐2,4‐dione (MND), a breakdown product of furanoid fatty acids suggested by other researchers to contribute to reversion flavor of SBO, was evaluated for its contribution to off‐flavor. The compound was synthesized in the laboratory and purified by gas chromatography (GC) on a Silar 10 C column. GC analysis of the purified MND on a nonpolar SPB‐1 column showed two well‐separated main peaks that have been suggested to represent keto and enol forms. Between these two peaks, a bridge of poorly resolved compounds may have represented various possible enol forms or an equilibration among these forms during the GC separation. MND had an intense straw‐like and frulty odor when evaluated at the outlet of a gas chromatograph. Sensory evaluation of MND in a mineral oil/water emulsion system showed that its flavor intensity increased almost imperceptibly with increased concentration (from 0.09 to 2.56 ppm). An explanation for this unusual flavor response may be that, when molecularly dispersed in air, MND has an intense odor, but when placed in a mineral oil or soybean oil emulsion, MND may exist in a form with relatively low flavor intensity, or it may be bound by the media. The concentrations of MND in SBO at various peroxide values were measured at 0 to 0.804 ppb, which were far less than concentrations tested in mineral oil/water emulsions during sensory evaluation and below published odor threshold values for MND in oil. Therefore, these results do not support the theory that furanoid fatty acids or MND contribute strongly to the reversion flavor of SBO.

COMPARISON OF BATTER-BREADED BEEF NUGGETS DEEP-FRIED IN COTTONSEED AND SOYBEAN OILS AND LIQUID SHORTENINGS

Restructured beef nuggets were batter-breaded and deep-fried in commercial cottonseed oil (CO), cottonseed liquid shortening (CLS), soybean oil (SO) and soybean liquid shortening (SLS) and stored at 4C for 0 or 4 days. Weight losses during frying and reheating were not significantly influenced by the frying medium used. No major sensory differences were noted among the different products except that, on day-0, nuggets fried in SLS had a “slight” warmed-over flavor due to the reversion flavor of the frying medium itself. On day-0, nuggets fried in CO or CLS had lower TBA values than those fried in SO or SLS. However, on day-4, nuggets fried in CLS or SLS had lower TBA values than nuggets fried in CO or SO. CLS may be the frying medium of choice among the four because of its ability to resist lipid oxidation in both fresh fried and stored nuggets.

Minor components responsible for flavor reversion of soybean oil

AbstractEdible refined, bleached and deodorized (RBD) soybean oil was fractionated by silicic acid column chromatography to identify minor components responsible for flavor reversion. Minor components from oil eluted with diethyl ether/n‐hexane (1:1) were compared with those from corn and canola oils. All vegetable oils contain free fatty acids, diglycerides and sterols as major ingredients in this fraction. However, unusual triglycerides consisting of 10‐oxo‐8‐octadecenoic acid and 10‐and 9‐hydroxy octadecanoic acids were detected in RBD and crude soybean oils.

Effects of minor components on flavor reversion in soybean oil.

Effects of minor components on flavor reversion in soybean oil.

3‐Methylnonane‐2,4‐dione – An Intense Odour Compound Formed during Flavour Reversion of Soya‐Bean Oil

AbstractNonane‐2,4‐dione and 3‐mehthylnonane‐2,4‐dione were identified in reverted soya‐bean oil. The odour threshold of the latter compound, which smelled “lard‐like, strawy, fruity”, was very low (0.01 ng/1 air) in comparison to that of the nonane‐2,4‐dione (3.9ng/1 air). Based on its odour properties and the result of an aroma extract dilution analysis, which have been recently reported (Fat Sci. Technol. 90, 332 [1988]), it was concluded that 3‐methylnonane‐2,4‐dione contributed very strongly to the reversion odour of soya‐bean oil. 3‐Methylnonane‐2,4‐dione, 3,7‐dimethyloctane‐2,4‐dione, decane‐2,5‐, ‐3,5‐and‐ ‐4,5‐dione, 3‐oxo‐ and 5‐oxodecanal were prepared as reference for the identification experiments. The spectroscopic (1H‐NMR, MS) and odour threshold data are reported.

Origin of Flavor Reversion in Soybean Oil

The susceptibility of soybean oil to flavor reversion was compared with that of other vegetable oils. The strongest flavor reversal was observed for soybean oil. That for a blended oil prepared by mixing other vegetable oils to the fatty acid composition similar to that of soybean oil was found to be much less. Furthermore, soybean oil triglyceride showed faint reversal and flavor deterioration compared with the original soybean oil in spite of its much less oxidative stability. Flavor reversal in soybean oil thus appears to possibly be closely related to trace components present in it.

Flavour Deterioration of Soya‐bean Oil: Identification of Intense Odour Compounds Formed during Flavour Reversion

AbstractAroma dilution analysis of a volatile concentrate isolated from reverted soya‐bean oil resulted in 11 odour compounds having high aroma values. Nine of these compounds were identified as: 3(Z)‐hexenal, octanal, 1‐octen‐3‐one, 1,5(Z)‐octadien‐3‐one, nonanal, 2(E)‐nonenal, 2(Z)‐nonenal, 3(Z)‐nonenal and 2(E),6(Z)‐nonadienal. 3(Z)‐Hexenal, the C9‐aldehydes and the two vinyl ketones contribute with high aroma values to the beany, grassy odour note of the reversion flavour.

包装茶の保存中に生成するオフ・フレーバー成分

Green tea off-flavor components were analyzed in two different types of tea storage pouches by gas chromatography. In a moisture proof pouch, the reversion flavor with green notes was found in sensory tests, and off-flavor components, such as 1-penten-3-ol, (Z)-2-penten-l-ol, (E, Z)-2, 4-heptadienal and (E, E)-2, 4-heptadienal, increased remarkably in storage of over three months. The amount of firing tea aroma components, such as 2-methylpyrazine, 2, 5-dimethylpyrazine and 1-ethyl-2-formylpyrrole, remained unchanged in four months storage. In an ordinary cellophane-polyethylene laminated pouch, a slightly acidic flavor was organoleptically detected, and acetic acid increased markedly in storage over three months. The off-flavor components did not increase in ordinary packaged tea as in the moisture proof package.

Isolation and identification of 2‐pentenylfurans in the reversion flavor of soybean oil

AbstractThe volatile flavor compounds in a reverted soybean oil with a peroxide number of 6.0 meq/kg were isolated by semicontinuous countercurrent vacuum steam distillation. Based upon the gas Chromatographic retention times and mass spectra of the four synthesized 2‐pentenylfurans, it was found that cis‐ and trans‐2‐(l‐pentenyl)furans and a mixture of cis‐ and trans‐2‐(2‐pentenyl)‐furans are present in reverted soybean oil. At least the greater portion of 2‐(2‐pentenyl)furans identified was cis‐isomer. These compounds may contribute to the reversion flavor of soybean oil.

Deodorization of edible oil

AbstractDeodorization is a high‐temperature, high‐vacuum steam‐distillation process to remove volatile, odoriferous materials present in edible fats and oils. This paper reviews and discusses the effect of temperature vs time, vacuum vs stripping steam, the importance of air exclusion, heating media, and flavor reversion.

A review of soybean oil reversion flavor

AbstractCrude soybean oil has a characteristic “greenbeany” flavor, which during refining, bleaching and deodorization is eliminated to produce a bland tasting, light colored oil. However, flavor returns during storage and has been characteristically called the “reversion flavor” of soybean oil. This deleterious characteristics flavor has influenced the utilization of soybean oil and its fatty acids. Several theories for the cause of reversion flavor include: (a) oxidation of linolenic acid; (b) oxidation of isolinoleic acid of the 9,15‐diene structure; (c) phosphatide reactions; (d) unsaponifiables; and (e) oxidative polymers. References are presented that support or contradict these theories. Recent publications concerning the isolation and characterization of the components of reversion flavor indicate slight oxidation of the fatty acids is the major cause. Techniques that are effective in increasing the flavor stability of soybean oil are presented.

The synthesis of 2‐(2‐pentenyl) furans and their relationship to the reversion flavor of soybean oil

Abstractcis‐ andtrans‐2‐(2‐Pentenyl)furans were synthesized and structures were confirmed by infrared, nuclear magnetic resonance and mass spectroscopy. Preliminary organoleptic evaluation of oil solutions of the compounds indicated that thecis isomer had a flavor threshold of ca. 0.25 ppm. with odor and flavor descriptions of beany, grassy and buttery at 0.50 ppm; and that thetrans isomer had a flavor threshold of ca. 0.50 ppm with odor and flavor descriptions of beany, grassy and buttery at 1 ppm and strong painty and metallic at 4 ppm. These compounds, if found in soybean oil through the autoxidation of linolenate, may contribute to the characteristic reversion flavor.