Biological effects due to changes in fats during heating

Changes in markers of lipid oxidation and thermal treatment in feed-grade fats and oils

BACKGROUND

Oxidized feed lipids have been shown to have detrimental effects on food animal growth and metabolism. The present study aimed to measure classes of lipid oxidation products (LOP) in feed-grade oils at temperatures representing production and storage conditions.

RESULTS

There were significant oil type × time interactions in the accumulation of primary and secondary LOP. At 22.5 °C, peroxide value (PV), a marker for the primary phase of lipid oxidation, increased most in fish oil (FO), followed by tallow (TL), soybean oil (SO), linseed oil (LO) and modified algae oil (MAO), whereas palm oil (PO) showed no appreciable increase in PV. Secondary LOP, such as p-anisidine value, hexanal, 2,4,-decadienal, polymerized triacylglycerols and total polar compounds, increased only in FO. At 45 °C, FO and SO produced both primary and secondary LOP, whereas MAO, PO and TL had slower rates of PV increase and no secondary LOP. At 90 °C and 180 °C, all oils except for FO accumulated both primary and secondary LOP.

CONCLUSIONS

Higher polyunsaturated fatty acid:saturated fatty acid oils and higher temperatures produced greater quantities of primary and secondary LOP. However, unrefined TL was more prone to oxidation at 22.5 °C than predicted, whereas LO was more stable than predicted, indicating that pro-oxidant and antioxidant compounds can markedly influence the rate of oxidation. Measuring both primary and secondary LOP will provide better information about the oxidative status of feed oils and provide better information about which classes of LOP are responsible for detrimental health effects in animals. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Improvement in antioxidant functionality and shelf life of yukwa (fried rice snack) by turmeric (Curcuma longa L.) powder addition

The physico-chemical, oxidative and sensory characteristics of fried rice snack, yukwa with different amounts of turmeric powder (Curcuma longa) were investigated. The moisture content of the pallet ranged from 16.47% to 19.84%. After frying the pallet, a slight decrease in the degree of expansion was obtained with increasing turmeric powder content. The textural properties of yukwa were not changed until the turmeric powder content reached 5%; however, over 8% addition induced a decrease in the hardness and an increase in the crispiness. Oxidative deterioration was effectively inhibited by turmeric powder addition, and more turmeric powder in yukwa led to higher free radical scavenging activity. Based on the sensory characteristics, a 5% addition of turmeric powder was the most acceptable for the yukwa product. In the correlation results among variables, the moisture content of the pallet proved to be the most important factor for yukwa quality.

Identification of E. dysenterica laxative peptide: a novel strategy in the treatment of chronic constipation and irritable bowel syndrome

Plants have contributed over the years to the discovery of various pharmacological products. Amongst the enormous diversity of herbs with remarkable medicinal use and further pharmacological potential, here in this report we evaluated pulp extracts from Eugenia dysenterica fruits and further identified the active principle involved in such laxative activity in rats. For protein isolation, fruits were macerated with an extraction solution following precipitation with (NH(4))(2)SO(4) (100%). After dialysis, the peptide was applied onto a reversed-phase semi-preparative HPLC column, and the major fraction was eluted with 26% and 66% acetonitrile. The evaluation of molecular masses by MALDI-TOF and Tris/Tricine SDS-PAGE of HPLC fractions showed the presence of a major peptide with approximately 7 kDa. The N-terminal amino acid peptide sequence was determined and showed no similarity to other proteins deposited in the Data Bank. Peptide from E. dysenterica was able to enhance rats' intestinal motility by approximately 20.8%, probably being responsible for laxative activity. Moreover, these proteins were non-toxic to mammals, as observed in histopathology and hemolytic analyses. In conclusion, results here reported indicate that, in the near future, proteins synthesized by E. dysenterica fruits could be utilized in the development of novel biotechnological pharmaceutics with laxative properties for use in chronic constipation and irritable bowel syndrome treatment.

Effect of vacuum-packaging storage on the quality level of ripened sausages

To investigate the influence of vacuum-packaging on both the sensory properties and the degradation level of their lipid fraction, some ripened sausages (30 days) were further stored for 40 days under vacuum-packaging and compared to sausages kept unpackaged for the same period of time. The same kind of sausages was used in both the trials. As for the sensory properties, after storage the unpackaged sausages showed significantly higher mean scores of red intensity and global flavour than vacuum-packed ones (p<0.01 and p<0.05, respectively) indicating a brighter red colour of meat and a greater overall appreciation by the panelists. Regarding the degradation of the lipid fraction, significantly higher values (p<0.01) of the free fatty acids were detected in the vacuum-packed samples, indicating a greater hydrolytic degradation of their lipid fraction as compared to the sausages stored unpackaged. The oxidative degradation of the fatty fraction, measured by the combined use of conventional (determination of peroxide value and TBA test) and non-conventional techniques (HPSEC analysis of the polar compounds of the lipid fraction) showed significant increases during storage for both the storage conditions considered but no significant differences were found between packaged and unpackaged sausages.

Serum liver enzymes profile of Wistar rats following chronic consumption of fresh or oxidized palm oil diets

The effect of chronic consumption of palm oil diets on serum levels of some liver enzymes in rat was investigated. Two groups of rats were fed on either fresh or thermally oxidized palm oil, mixed at 15% level for 18 weeks and their effects on serum levels of alkaline phosphatase (EC 3.1.3.1), aspartate aminotransferase (EC 2.6.1.1) and alanine aminotransferase (EC 2.6.1.2) enzymes were compared with a control group receiving normal rat feed. The levels of alkaline phosphatase (ALP) in the two groups were significantly higher (P < 0.05-0.01) than control. Mean ALP levels were significantly different in the two test groups (P < 0.05). Similarly, there was significant elevation (P < 0.05-0.01) of aspartate aminotransferase (AST) levels in oxidized oil-fed and fresh oil-fed groups when compared with the control. The mean alanine aminotransferase (ALT) level was significantly higher (P < 0.01) in the oxidized oil-fed group than the control and fresh oil-fed groups. The results indicate that chronic consumption of thermoxidized palm oil, with its accompanying hazardous free radicals, may be more injurious to liver cell integrity than fresh palm oil.

Biogenesis of hepatic acute-phase response to trauma

The bioorganic pathway(s) of hepatic acute-phase response in rat to single and compounded traumata triggered either by chemical or physical injury has been re-evaluated for the purpose of advancing a better understanding of mechanisms of hepatic regeneration. These insights would be useful in cases of liver cirrhosis and end-stage liver diseases and may allow avenues of surgical management other than liver transplantation. Mechanisms of acute-phase response in rat to a single inflammatory stimulus, e.g. intoxication with phalloidin, alpha-amanitin, subcutaneous administration of carageenan, subcutaneous implantation of Yoshida sarcoma or i.p. administration of Zajdela ascites are discussed and compared with (a) acute-phase response to intoxication by various factors leading to the development of liver cirrhosis, and (b) acute-phase response of nascent hepatocytes where hepatic regenerative activities were induced by chemical intoxication or surgical partial hepatectomy. Interestingly, hepatic acute-phase response was not limited only to these injuries outlined above but also to psychological conditions.

Comparison of thermally oxidized lipids and acetaminophen with concurrent consumption of ethanol as inducers of liver cirrhosis

The mechanism(s) of liver damage initiated by ingestion of toxic components of thermally oxidized lipids was compared in a rat model with the documented mechanisms of hepatic failure and necrosis initiated by acetaminophen. Acetaminophen (50 mg/kg body weight) or oxidized lipids (0.15 ml oxidized trilinolein or 1.05 ml oxidized butter oil per rat) were intubated at 12-h intervals to rats. Treated rats were allowed free access to food and water containing 3% ethanol. Changes in relative concentration of acute-phase plasma proteins, determined by two-dimensional (2D) immunoelectrophoresis, were taken as a marker of liver damage. In contrast to simple inflammation, acute-phase plasma proteins in this study disproportionately increased or decreased as histological damage of the liver due to intubation oxidized lipids or acetaminophen. Histological examination of liver of rats intoxicated with oxidized lipids revealed severe liver cirrhosis at the end of the trial, where the remaining viable hepatocytes were separated in a matrix of collagen. [3H1]Thymidine incorporation in hepatic DNA of acetaminophen or oxidized lipid intoxication increased in the early stages of intoxication, indicative of regenerative activity of the liver. Further progression of the cirrhosis inhibited continued liver regeneration and [3H1]thymidine incorporation into hepatic DNA. The cirrhotic liver at this stage failed to regenerate to the original mass upon 75% partial hepatectomy. Therefore, it may be concluded that hepatic necrosis produced by oxidized lipids or by acetaminophen may have similar mechanisms.

A 91-day feeding study in rats with heated olestra/vegetable oil blends

A 91-day feeding study in rats was conducted to assess the potential toxicity of heated olestra/vegetable oil blends. Olestra is a mixture of the hexa-, hepta- and octa- long-chain fatty acid esters of sucrose. The blends tested were 35/65 olestra/vegetable oil (w/w), pan-fried at 380 degrees F for 30 min to simulate home-use conditions and 75/25 olestra/vegetable oil, deep-fried at 365 degrees F for 84 hr to simulate extended food-service use. Vegetable oil, prepared using both heating conditions, unheated vegetable oil and unheated olestra/vegetable oil blends served as controls. The olestra/vegetable oil blends and vegetable-oil control were generally fed at 10% (w/w) of the diet. Two further groups received the heated olestra/vegetable oil blends at 5% of the diet. Survival, clinical signs, body weight, feed consumption, feed conversion efficiency, organ weights, organ-to-body-weight ratios, haematological parameters and histomorphology were evaluated. No adverse effects from the ingestion of heated olestra/vegetable oil blends were detected. These findings indicate that heated olestra was non-toxic and, in this respect, no different from unheated olestra or heated or unheated vegetable oil.

Biological observations from feeding heated corn oil and heated peanut oil to rats

Five groups of male weanling rats were provided purified diets containing 15% by weight of either fresh or laboratory-heated corn oil (FCO, HCO) or fresh, laboratory-heated, or commercial pressure deep-fry peanut oil (FPO, HPO, PPO). Total weight gain, feed consumption, and feed efficiency were consistently greater for the FCO, FPO, and PPO groups. Although relative heart weights were unaffected, the HCO and HPO produced elevated liver and kidney weights. The dietary fats had no effect on the hematological status of the animals or the proportions of cells comprising the total leukocytes of the blood. Physical, chemical, and microscopic evaluation of the urine detected no pathologic conditions. Rats fed diets containing HCO or HPO demonstrated toxicity of thermally oxidized fats by the appearance of diarrhea, dermatitis, seborrhea, and hair loss. Histological examinations revealed injury of the thymus by all fat samples except the FCO; the liver was damaged by the HCO, HPO, and PPO, and the testes and epididymides by HPO and PPO. In the latter case there was complete cessation of spermatogenesis.

Effect of ingestion of thermally oxidized frying oil on peroxidative criteria in rats

Thermally oxidized rapeseed oils (4 levels of deterioration; used by a manufacturer of fried fish paste in a conventional manner) were fed to rats at a practical level of concentration. Rats were fed a diet ad libitum for 13 weeks that contained 15% of a test oil. The effects of the diet on several biochemical criteria related to peroxidative alterations were investigated. In groups given thermally oxidized oils relative liver weight, relative kidney weight, thiobarbituric acid-reactive substances (TBA-RS) in the liver and reduced glutathione content were increased significantly in proportion to the degree of deterioration of the oil, compared with the group given fresh oil. Tocopherol contents in both serum and liver were decreased considerably in proportion to the deterioration level of the supplied oils. The above criteria correlated well with various deterioration indices of the oil. For instance, TBA-RS was well correlated (p less than 0.001) with petroleum ether-insoluble oxidized fatty acid (r = 0.9191), column chromatographically separated polar fraction (r = 0.9056), glyceride dimer fraction (r = 0.9023) and carbonyl value (r = 0.8647).

Cytotoxicity of thermally oxidized fats

The effects of oxidized fat components (free fatty acids from the distillable nonurea adductable fraction) isolated from heated corn oil or heated olive oil on the morphology and growth of heart cells in primary culture were investigated. The free fatty acid fractions isolated from the fresh fats served as controls. Different concentrations of the fat fractions (20, 60, and 100 micrograms/ml) were added to the medium in the form of an emulsion with bovine serum albumin (Fraction V, poor in unesterified fatty acids). In the cell cultures treated with heated fats, intracellular lipid accumulation, increased cytoplasmic vacuolization, mitotic aberrations, pyknotic cells, and decreased mitosis were observed and were more pronounced in the case of the heated olive oil. These cytotoxic effects increased with higher concentrations of heated fats in the medium. The fresh fats also produced intracellular lipid accumulation, reductions in mitosis, and changes in the nucleus and cytoplasm, at the higher levels. These effects were greater in fresh olive oil-treated cultures. These observations indicate that oxidized fat components interfere physically or biochemically with normal cell functions resulting in pathological changes.

Some toxic compounds produced in food by cooking and processing

Both cooking and processing of food can produce toxic compounds in food, if the appropriate precursors are present. N-Nitrosamines, polycyclic aromatic hydrocarbons and phenolic compounds, lipid polymerisation products resulting from deep-fat frying, lipid oxidation products, Maillard-browning products and other products of protein reactions are discussed as well as their formation, concentration and control. The conclusion points out that contamination of human food is almost impossible to avoid and must be considered together with the beneficial effects of food processing on food safety, flavour, shelf-life and convenience.

Chemical and biological properties related to toxicity of heated fats

Heating of fats brings about measurable changes in their chemical and physical characteristics. Heat is applied in processing for food manufacture, such as during hydrogenation of oils with a catalyst, and in frying for meal preparation. Partially hydrogenated products generally contain substantial quantities of geometric and positional isomers of the original unsaturated fatty acids. During deep-fat frying, when the fat is used repeatedly, oxidative and thermal effects result in the formation of many volatile and nonvolatile products, some of which are potentially toxic, depending on the level of intake. Because of concern about the types of changes that take place in fats during oxidative and thermal deterioration and the effects the derivatives could have on the consumer, many chemical and biological studies have been carried out. Experimental findings indicate that any potential danger to the consumer is relative to the severity of the overall treatment of the fat. In some studies we evaluated biological effects on rats of trans fatty acid in the diet and of concentrates of fatty acid derivatives produced in thermally oxidized fats. trans-Octadecenoic acid changed the concentrations of the phospholipid classes in the liver lipids, and interfered with conversion of the essential n - 6 series of fatty acids to higher members. Compared to oleic acid, elaidic acid was preferentially incorporated into the phospholipids instead of the triacylglycerols and was also concentrated in the lipoprotein fractions. Administration of non-urea-adductable concentrates from thermally oxidized fats produced cellular damage in hearts, livers, and kidneys of the animals. Since even practical processing and frying conditions can produce some nutritionally undesirable products, a concerted effort should be made to minimize substantial accumulation of these in our dietary fats.