“grassy” or “paint-like” flavors in food ( Frankel, 1983 ). Hydrolysis of triacylgycerides yields free fatty acids. Quantifying the peroxide value, hexanal content, and free fatty acids provides insight into the amount of lipid degradation that has
hydrocarbons. Hydrolysis of triacylgycerides yields free fatty acids. The walnut harvest occurs once a year in autumn, when the nuts are mature for harvest, using a mechanical shaker. Some orchards are shaken twice to maximize yield. Walnuts are stored in
cultivar. Fig. 1. Changes in free fatty acid (FFA) content (percent oleic acid) of oils obtained from olives stored at different temperatures (4 °C, 10 °C, and room temperature) for different periods of time (1, 5, 9, 16, and 23 d). (A) ‘Barnea’, (B
concentration, they are not taken up readily. Aldehydes as natural FA metabolites ( Drawert, 1975 ) are therefore more suitable to be applied as aroma precursors. Fig. 5. Comparison between the concentrations of total and free fatty acids of apple and strawberry
Developmental changes in total cuticle and cuticular constituents were studied with `Delicious' fruit. Total wax (0.31 mg/cm2) and total cutin (0.54 mg/cm2, including carbohydrate polymers) were low in young fruit. They increased during fruit growth and reached 1.41 and 2.47 mg/cm2 of fruit peel at harvest, respectively. During fruit ripening at 20 °C, total cutin did not change, but total wax increased rapidly and reached 2.15 mg•cm-2 at 6 weeks. The increase of cuticular wax paralleled the increase of internal ethylene in fruit. Wax was separated by column chromatograph into four portions, hydrocarbons and wax esters, free alcohols, free fatty acids, and diols. More than half of the diols was ursolic acid. During fruit development, more hydrocarbons and diols accumulated in cuticle than free fatty acids and alcohols. During fruit ripening, all of the four portions increased, coincident with the climacteric rise in ethylene, but the increase rates of free fatty acids and alcohols were higher than those of other portions. Aminoethoxyvinylglycine (AVG, 220 mg•L-1) preharvest treatment inhibited internal ethylene synthesis to below 0.5 μL•L-1 during 6 weeks at 20 °C, and also inhibited wax accumulation. Ethephon (200 mg/L) preharvest treatment increased ethylene production and accelerated wax accumulation. α-farnesene accumulation coincided with increased internal ethylene and paralleled free fatty acid and alcohol accumulation.
refined oil. Table 5. Olive oil quality from one sample each of three cultivars (Arbequina, Arbosana, and Koroneiki) harvested in 2013 and analyzed for free fatty acids (FFA), peroxide value (PV), K value of ultraviolet absorption at 232 nm [K232
Cauliflowers (Brassica oleracea) were irradiated at 0, 2, and 4 kGy and stored 8 days at 13°C. Development of yellow color and browning of the in florescence, increase in membrane electrolyte leakage and reduction of protein recovery in microsomal membranes were observed over the storage period. Changes in membrane free fatty acids, lipid phosphorus content, peroxydation level, and fatty acid composition of polar lipids also occurred. These results indicate an important modification of cellular membranes. The direct effect of gamma rays on membrane lipids via free radical production and subsequent destabilization of the lipid bilayer during storage could be responsable for earlier onset of senescence.
Pecans [Carya illinoinensis (Wangenh. C.) Koch] were harvested weekly for 9 and 7 weeks until normal harvest time during 1986 and 1987, respectively. Kernels were tested for chemical, physical, and sensory properties. Moisture decreased from 13% at initial harvest time to 4% to 6% by normal harvest. Free fatty acids decreased from 0.5% to 0.2% by the third week before normal harvest. Tannins fluctuated, but averaged about 0.8%. Hue angle remained constant from the fourth week to normal harvest. Shear force increased from 90 to 135 N by the second week before normal harvest. Pecans can be harvested about 2 weeks before normal harvest without significant quality deficiencies.
The pungency in hot peppers [Capsicum annuum (L.) var. annuum] is mostly due to two capsaicinoids, capsaicin (CAP) and dihydrocapsaicin (DC), which are amide derivatives of vanillylamine and 8-methyl-6-nonenoic acid (E) or 8-methyl-nonanoic acid (A), respectively. During our investigation of the mechanism of capsaicinoid-specific metabolism in pepper fruit, we have developed a method to extract, purify, and quantitate these fatty acids from the free fatty acid pool in placental tissue. Fresh placenta was ground using a mortar and pestle and extracted with diethyl ether. Fatty acids were methanolysed and fatty acid methyl esters were quantitated using GC with capric acid as internal standard. Capsaicinoids accumulated in the same placenta were extracted with N,N-dimethylformamide (DMF) and quantitated using HPLC. The lipid fraction had to be separated from capsaicinoids, since capsaicinoids yielded about 10% of their respective fatty acids during methanolysis. An aminopropyl column was used to separate capsaicinoids from free fatty acids. Extraction recovery for both fatty acids was greater than 70%. This procedure is being used to quantitate fatty acid precursors for capsaicinoid biosynthesis in pepper placenta. We will demonstrate use of this procedure with pepper selections varying in CAP/DC ratio to evaluate the effect of metabolic precursors on capsaicinoid metabolism.
Pecans (Carya illinoinensis) are full of unsaturated fatty acids, which are subject to oxidative cleavage. This results in the development of rancid off-flavors, which render the nuts unmarketable. For this reason, pecans must be stored under costly refrigerated conditions. Furthermore, pecans usually undergo retail distribution and marketing at ambient conditions, which promote development of off-flavors. Application of cellulose-based edible coatings reduced off-flavor, and improved overall flavor scores while adding shine to the nuts during 14 months of storage under ambient conditions. Development of rancidity involves hydrolysis of glycerides into free fatty acids, oxidation of double bonds of unsaturated fatty acids to form peroxides and then autooxidation of the free fatty acids once the peroxides reach a sufficient level to perpetuate this reaction. One of the products of autooxidation is hexanal which is, thus, a good indicator of rancidity. Analysis of pecans by gas chromatography revealed that hexanal levels were reduced in coated nuts by 5- to over 200-fold compared to uncoated controls, depending on the coating treatment. Some of the coating treatments affected nut color, but overall flavor and appearance were improved by certain formulations.