Lipids bitterness

The importance of lipophilicity to bitterness has been well established, both directly and indirectly. The importance of partitioning effects in bitterness perception has been stressed by Rubin and coworkers, and Gardner demonstrated that the threshold concentration of bitter amino acids and peptides correlates very well with molecular connectivity (which is generally regarded as a steric parameter, but is correlated with the octanol-water partition coefficient ). Studies on the surface pressure in monolayers of lipids from bovine, circumvallate papillae also indicated that there is a very good correlation between the concentration of a bitter compound that is necessary in order to give an increase in the surface pressure with the taste threshold in humans. These results and the observations of others suggested that the ability of bitter compounds to penetrate cell membranes is an important factor in bitterness perception. 

The first utilization of the term artificial tongue dates to 1978, when H.W. Harper and M. Rossetto presented an apparatus based on conductance measurements able to mimic the taste stimulus delivery systems (Harper and Rossetto, 1978). This pioneering work has represented an isolated study for several years. The first example of a factual taste sensor was developed, in fact, by Toko and coworkers in 1990 (Hayashi et ah, 1990 Toko et ah, 1990). It was based on ion-sensitive lipid membranes and it was claimed to be able to respond to the basic tastes of the human tongue sour, sweet, bitter, salt, and umami. 

Standards and Controls. In all experiments, the 85 g standard patties were made from freshly ground top round steaks (excess fat trimmed) and immediately frozen in covered glass petri plates until the day of the assay. The fat content was routinely from 4-5%, determined by the method of Koniecko (57). The standards generally had relatively low values for hexanal, total volatiles (TV) and TEARS, and low intensity values for painty (PTY), cardboardy (CED), sour (SUR) and bitter (ETR). These results indicated the absence of lipid oxidation and no formation of off-flavors. As expected, the desirable flavor notes, cooked beef/brothy (CEE), beefy/meaty (EM), brothy (ERO), browned/caramel (ERC) and sweet (SWT) had high intensity values. 

The chemical, instrumental and sensory data presented above indicated that storage of cooked beef affects the lipid composition and concomitantly, the flavor of beef. The data also indicated that primary tastes like bitter and sour are affected by storage. 

The changes in the protein composition and flavor of "cooked" and "cooked- -stored" beef seemed to be related to degradation by free radical species induced during lipid oxidation 1-10, 16, 22, 23), Based on the information presented in the aforementioned publication, it seemed reasonable to suggest that the appearance of "bitter" and "sour" tastes and the disappearance of "meaty" and "beefy" flavors were a result of the activity of the free radicals derived from lipid oxidation on flavor proteins (2, 24-28),... 

One method to realize the taste sensor may be the utilization of similar materials to biological systems as the transducer. The biological membrane is composed of proteins and lipids. Proteins are main receptors of taste substances. Especially for sour, salty, or bitter substances, the lipid-membrane part is also suggested to be the receptor site [6]. In biological taste reception, taste stimulus changes the receptor potentials of taste cells, which have various characteristics in reception [7,8]. Then the pattern constructed of receptor potentials is translated into the excitation pattern in taste neurons (across-fiber-pattem theory). 

The DOPH membrane did not respond to picric acid, which is a strong bitter substance. We, therefore, studied a response by a different lipid membrane [12], The synthesized lipid is dialkyl-dimethyl-ammonium, which has two hydrocarbon chains and an ammonium group positively charged. This lipid was cast on a silicon film with one hole, 100 pm in diameter. It was shown that picric acid changes the membrane potential of this membrane largely. 

Typical five primary taste substances, HC1 (sour), NaCl (salty), quinine-HCl (bitter), sucrose (sweet) and MSG (umami) were studied [16]. In general, the response of each lipid membrane was nonspecific to various taste substances. 

Phenolics. The phenolics of citrus represent a varied and widely studied class of compounds. They range from the lipid-soluble methoxylated coumarins and psoralens to the water-soluble glycosides of the flavanones and flavones. They include the intensely bitter naringin and the highly insoluble hesperidin. Different classes within the group have characteristic UV spectra which have been used to detect adulterations in juices and oils. 

Ve now investigated the hypothesis if the bitterness of lipids - and carbohydrates - could also be linked to hydro-phobic interactions (82,8 ). Let us look first at the questions of hydroxylated fatty acids. 

Hydrophobic interactions can also be used to provide information on the bitterness of lipids. 

Hydrolytic rancidity results from the hydrolytic degradation of milk lipids. The hydrolysis is catalyzed by lipases and produces free fatty acids (FFAs), some of which have a low flavor threshold and can cause unpleasant flavors in milk and milk products. These flavors are variously described as rancid, butyric, bitter, unclean, soapy or astringent. The lipases involved are of two types indigenous milk enzyme(s) and enzymes of microbial origin. 

Lupines are known as rich leguminosae in lipids and proteins. This makes them very interesting if they were produced in a large industrial scale. However the presence of bitter and poisonous quinolizidine alkaloids is the main obstacle to overcome for a broader utilisation. 

Lupines have relatively large seeds which contain up to 40-50% protein, up to 20% lipids, and 2-8% alkaloids. To use lupine seed for animal or human nutrition, Homo sapiens, for several thousand years, used to cook the seeds and leach out the alkaloids in running water. This habit has been reported for the Egyptians and Greeks in the Old World, and for the Indians and Incas of the New World. The resulting seeds taste sweet, in contrast to the alkaloid-rich ones which are very bitter. In Mediterranean countries people still process lupines in the old way, and sometimes the... 

Liposomes, like single lipid coats, have been examined for their ability to deliver peptides and proteins. Encapsulation of casein peptides in liposomes (0.5-1 pm in size at a rate of 50%-60%) significantly reduced bitterness and increased stability (Morais et al. 2005). Hsieh et al. (2002) showed that a-amylase can be protected against the action of pepsin at low pH, demonstrating the protection that may be offered during transit through the stomach. 

Carblnoxamine Maleate, USP. The oily, lipid-solubic free base of carblnoxamine is available as the bitter bima-Icate salt. (r/./)-2- />-chloro-a-f2-(dimethylamino)cthoxy -... 

Drewnowski A, Henderson SA, Shore AB (1997) Genetic sensitivity to 6-n-propylthiouracil (PROP) and hedonic responses to bitter and sweet tastes. Chem Senses 22 27-37 Drewnowski A, Henderson SA, Cockroft JE (2007) Genetic sensitivity to 6-n-propylthiouracil has no influence on dietary patterns, body mass indexes, or plasma lipid profiles of women. J Am Diet Assoc 107 1340-1348... 

Properties Orange-yellow crystals bitter taste. Mp 282C (decomposes). Slightly soluble in water and alcohols insoluble in lipid solvents stable to heat in dry form and in acid solution. Stable to ordinary... 

Verschuere et al. [25] observed a similar trend in the extraction of essential oils and bitter acids of hops when using samples as small as 0.25 grams. They observed, "Compared to conventional methods for extraction of alpha-acids and beta-acids, % rsd s are higher with SFE. Typical values are in the order of 10 % for 6 replicates on the same hop sample. This is due to the small sample size requirements if contamination problems have to be avoided. With the extractor used and taken into consideration that the concentration of the bitter acids in hops range as high as 10 %, 250 milligram sample size is the maximum which can be extracted without breakthrough or contamination (of the lipid-free... 

Taste. Taste Is the human perception of chemicals In the mouth due to their Interaction with receptors on the tongue. Taste consists of four dimensions sweet, salty, sour and bitter. Taste Is affected by odor and texture, which makes it a complicated, subjective quality attribute, difficult to measure objectively (22). In fruits and vegetables, taste Is mostly determined by the types and amounts of carbohydrates, organic acids, amino acids, lipids and phenolics (5.71). CA combinations, to the degree that they modify changes in these constituents, can affect the taste of stored fruits and vegetables. Usually, extremely low O2 or high CO2 will result In off-flavors and reduced quality due to anaerobic respiration. The specific effect of CA on flavor depends on the crop Involved (2). 

Synthetic lipid (dioctadecyldimethyl ammonium polystyrene and dimyristoylphosphatidyl-ethanolamine) cast from solution onto piezoelectric quartz crystals (5/z, ordered layers) IgG covalently linked to thiolated, carbodiimide-activated gold electrodes on piezoelectric quartz crystals Bitter/sweet compounds anti-IgG [1]... 

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