Proximate Composition and Nutritional Attributes of Ready-to-Cook Catfish Products

To increase the demand for U.S. farm-raised catfish, five healthy, convenient ready-to-cook products were developed to expand consumers’ options beyond basic fresh or frozen fillets. Five new catfish products were produced, consisting of one hundred samples of each, including three size-types of Panko-breaded fish products (strips, center cuts of regular fillets, and center cuts from Delacata fillets) and two marinated products (sriracha and sesame-ginger). The breaded products were to be prepared by baking for convenience over traditional frying methods, while the marinated products were to be microwaved as healthy and convenient products. The nutrient content of the samples was analyzed, including protein, moisture, fat, fiber, ash, and carbohydrate, as well as minerals, amino acid, and fatty acid constituent content, with associated atherogenic index (AI) and thrombogenic index (TI), showing unique differences between the Panko-breaded and marinated products. In addition, a trend was observed showing an increase in moisture, protein, ash, and carbohydrate percentages, and a decrease in lipid content related to the volume-to-surface-area ratio, having the order of strips < standard fillets < Delacata fillets.

Active synthesis of C24:5, n-3 fatty acid in retina

The formation of 14C-labelled long-chain and very-long-chain (n-3) pentaenoic and hexaenoic fatty acids was studied in bovine retina by following the metabolism of [14C]docosapentaenoate [C22:5, n-3 fatty acid (22:5 n-3)], [14C]docosahexaenoate (22:6 n-3), and [14C]acetate. With similar amounts of 22:5 n-3 and 22:6 n-3 as substrates, the former was actively transformed into 24:5 n-3, whereas the latter was virtually unmodified. Labelled 24:5, 26:5, 24:6 and 22:6 were formed from [1-14C]22:5 n-3, showing that pentaenoic fatty acids including 24:5 n-3 can be elongated and desaturated within the retina. When retinal microsomes were incubated with [1-14C]22:5 n-3, 24:5 n-3 was the only fatty acid formed. In retinas incubated with [14C]acetate, 24:5 n-3 was the most highly labelled fatty acid among the polyenes synthesized, 24:6 n-3 being a minor product. Such selectivity in the elongation of two fatty acids identical in length, 22:5 n-3 and 22:6 n-3, despite the fact that 22:5 is a minor and 22:6 a major fatty acid constituent of retina, suggests that the active formation of 24:5 n-3 plays a key role in n-3 polyunsaturated fatty acid (PUFA) metabolism. This compound might give rise to even longer pentaenes via elongation, and to the major PUFAs of retina, 22:6 n-3, by 6-desaturation and chain shortening. Of all retinal lipids, a minor component, triacylglycerol (TG), incorporated the largest amounts of [14C]22:5 and 22:6. TG also concentrated most of the [14C]24:5 formed in retina, whether from [14C]22:5 n-3 or from [14C]acetate, suggesting an important role for this lipid in supporting PUFA metabolism and the synthesis of 22:6 n-3.

The effect of sn-2 fatty acid substitution on phospholipase C enzyme activities

The human monocyte cell line U937 expresses phospholipase A2 and phospholipase C activities and produces eicosanoids. The phospholipase C (PLC) activity exhibits substrate preference for phosphatidyl-choline (PC), rather than phosphatidylinositol or phosphatidylethanolamine. In order to characterize the PLC activity found in these cells, the effects of substitution of the sn-2 fatty acid on this activity were examined. PC substrates with palmitic acid (PC-2P), oleic acid (PC-2O), arachidonic acid (PC-2A) and linoleic acid (PC-2L) at the sn-2 position were used. The sn-1 fatty acid was palmitic acid. PC-2L and PC-2A with the longer-chain less-saturated fatty acids linoleic acid and arachidonic acid esterified at sn-2 were found to be better substrates for PLC activity than PC-2P or PC-2O in these cells. This preference was maintained even when substrate phospholipid was solubilized in non-ionic, anionic, cationic and zwitterionic amphiphiles. Furthermore, when a 500-fold excess of 1,2-diolein or 1,2-dipalmitin was added to the reaction, the specificity of the PLC activity for PC-2A and PC-2L remained unchanged. When similar experiments were performed with phosphatidylinositol as a substrate, we did not observe any effect when the sn-2 position was altered. These data show that the fatty acid constituent at the sn-2 position affects the observed PLC activity when phosphatidylcholine, but not phosphatidylinositol, is used as a substrate by these cells.

Activity of Synthetic Phospholipids in Blood Coagulation

Summary1. An investigation was made into the activity of synthetic phospholipids on blood coagulation in vitro, utilizing synthetic substances including phosphatidyl ethanolamine and phosphatidyl serine containing a poly-unsaturated fatty acid constituent.2. Applying a one-stage recalcification test, phosphatidyl serine was found to act at high concentrations as anticoagulant. No clot-promoting activity was observed after addition of individual phospholipids. However, several combinations of phospholipids, e.g. phosphatidyl ethanolamine with phosphatidyl serine or certain mixtures of lecithin with phosphatidylserine, shortened the clotting time.3. In the thromboplastin generation test phosphatidyl ethanolamine exhibited some acceleratory activity without being able, however, to replace crude brain cephalin completely. However, optimal coagulant activity was produced by mixtures of synthetic phospholipids viz, phosphatidyl ethanolamine with phosphatidyl serine, phosphatidic acid or (isolated) cardiolipin and by certain combinations of lecithin and phosphatidyl serine.4. In both assay systems the maximum activity of each phospholipid combination was found to be related within certain limits to the ratio of both compounds. It is concluded that the coagulant activity of phospholipids in vitro is not to be attributed to a certain type of phospholipid or a defined mixture. The results obtained with the synthetic compounds appear to support the view that a particular negative surface charge of the phospholipid micelles is a prerequisite for maximal clot-promoting activity of phospholipids.