Stability of vitamins A and C in fortified yogurt.

Plain and raspberry flavored low fat yogurt samples were fortified with various commercial forms of vitamins A and C under actual production conditions. Immediately after processing, yogurt samples were kept at 3 degrees C for 6 wk and were analyzed biweekly for pH, titratable acidity, and vitamins A and C. Data revealed that both vitamins decreased gradually in fortified yogurt with vitamin C decreasing at a higher rate than vitamin A. However, a fortification level of 10,000 IU of vitamin A and 300 mg of vitamin C per 227 g container of plain or flavored yogurt provided at least 100% of the US recommended daily allowance of both vitamins after 6 wk storage at 3 degrees C. This level of fortification did not significantly change pH, titratable acidity, or sensory characteristics of yogurt samples.

Liquid chromatographic quantitation of chicken and turkey in unheated chicken-turkey mixtures.

A simple and rapid liquid chromatographic (LC) method has been used to quantitate chicken and turkey in unheated chicken-turkey mixtures. The LC method is sensitive and detects as little as 1% chicken or turkey. It reliably quantitates 5-100% chicken or turkey in unheated poultry mixtures. The method applies also to chicken or turkey which has been frozen, but does not apply to heat-treated poultry meats.

Liquid chromatographic identification of meats.

Raw beef, pork, veal, lamb, chicken, turkey, and duck have been identified with a liquid chromatographic (LC) method. Meat samples are blended in water, and soluble proteins in the aqueous blends are separated by the LC method. Meat cuts and parts from same species had similar chromatographic profiles and differed only quantitatively. However, meat cuts or parts from different species resulted in different chromatographic profiles. The qualitative and quantitative chromatographic differences among meat species were used for their identification. The LC method applies only to fresh and frozen meats. It is simple, rapid, and reliable, and can be used for quantitative detection of meat species in unheated meat blends.

Improved liquid chromatographic determination of riboflavin in milk and dairy products.

Reported here is a simple liquid chromatographic (LC) method for the determination of riboflavin in milk (liquid, evaporated, and dry), yogurt, and cheese. The method involves passing liquid samples or filtrates of semisolid and solid samples through a C18 cartridge. Retained riboflavin is then eluted with an aliquot of 50% methanol in 0.02M acetate buffer of pH 4. A volume of the eluate is injected into the LC system consisting of a C18 column, a solvent of water-methanol-acetic acid (65 + 35 + 0.1, v/v) with a flow rate of 1 mL/min, and a UV detector set at 270 nm. The method is precise and accurate and compares favorably with the present AOAC method. Moreover, it involves fewer sample preparation steps and has a total analysis time of less than 1 h.

Liquid chromatographic determination of ascorbic acid in foods.

Ascorbic acid has been determined quantitatively in a variety of fresh and frozen fruits and vegetables, fresh and fortified canned juices, and powdered drinks by liquid chromatography (LC). The method consists of blending the sample in a solution of 0.05% EDTA in 0.2N H2SO4, centrifuging or filtering the mixture, then injecting a portion into the LC system. An Aminex HPX-87 LC column was used with 0.009N H2SO4 as solvent with a flow rate of 0.5 mL/min. Detection was at 245 nm. The method is simple and sensitive, and yields a high recovery. It compares favorably with the AOAC method, and has the advantage of being more accurate for samples with interfering pigments.

High performance liquid chromatographic determination of caffeine in decaffeinated coffee, tea, and beverage products.

A method was developed for determining caffeine in decaffeinated coffee, tea, and beverage products by high performance liquid chromatography (HPLC). The HPLC system consisted of a Bio-Sil ODS-5S C18 column, methanol-water (25 + 75) mobile phase at 1 mL/min, and a UV detector. The method is simple and specific. Caffeine recoveries were 93.8-98.3% and coefficients of variation were 0.90-2.25%.

High performance liquid chromatographic determination of Bifidobacterium bifidum growth factors in human milk.

An isocratic high performance liquid chromatography (HPLC) method has been developed for the determination of Bifidobacterium bifidum growth factors in human milk. The method involves the gradual addition of 3 volumes of ethanol to the milk sample, filtration, and analysis of the growth factors in the filtrate by HPLC. The HPLC system consisted of a carbohydrate analysis column, a water-acetonitrile (70 + 30) solvent system, a flow rate of 1.0 mL/min, and a refractive index detector. The method is simpler and requires less time than the present microbiological method. Moreover, it revealed for the first time the presence of 2 separable growth factors in all human milk samples tested. The HPLC method developed is sensitive and can be used to monitor the type and the amount of growth factors in mothers' milk during lactation.

Effects of temperature and time on mutagen formation in pan-fried hamburger.

Mutagenic activity generated in hamburger during pan-frying is dependent upon both temperature and time, with temperature appearing to be the more important variable. Uniformly prepared frozen hamburger pattie (115 g; 19% fat) were fried under carefully controlled conditions at 143 degrees C, 191 degrees C and 210 degrees C. Mutagenic activity assayed with the Ames test was not detected in uncooked hamburger, and in hamburger fried at 143 degrees C mutagenic activity remained low at all times studied (4--20 min). In contrast, frying at 191 degrees C or 210 degrees C for up to 10 min resulted in the generation of considerably higher levels of mutagenic activity. Mutagenic activity in fried hamburgers sold at selected restaurants ranged from very low to moderately high. Evidence is also presented for mutagenic inhibitory activity in uncooked and fried hamburger. Mutagenic inhibitory activity decreased mutagenesis mediated by liver S-9 from normal rats but not from Aroclor 1254-treated rats.

Reduction of aflatoxins B1 and B2 with sodium borohydride.

Reduction of aflatoxin B1 and aflatoxin B2 with sodium borohydride quantitatively yielded new fluorescent derivatives, designated as aflatoxin RB1 and aflatoxin RB2. Mass spectrometric data showed that RB1 and RB2 were trihydroxy derivatives of B1 and B2, respectively. Nuclear magnetic resonance analysis revealed that new chemical shifts were present in aflatoxins RB1 and RB2 in addition to those of the parent aflatoxins. The new compounds had lower melting points and different ultraviolet and infrared spectra compared to aflatoxins B1 and B2 and the monohydroxy derivative aflatoxicol. They were lses toxic to chick embryos than the parent toxins. Since the reduction yields were quantitative and since the reduction products could be detected at low levels comparable to those for B1 and B2, the reduction reaction could be used as a confirmatory test for both aflatoxins B1 and B2. Preliminary results obtained from gas-liquid chromatography (GLC) analysis of the trimethylsilyl derivatives of aflatoxins RB1 and RB2 indicated that these compounds could furnish the basis for developing an analytical GLC method for aflatoxins B1 and B2.

New confirmatory test for aflatoxins B1 and B2.

A new confirmatory test for aflatoxins B1 and B2 is described. The test involves treatment of aflatoxins with excess sodium borohydride for 10 min at room temperature, to yield a fluorescent trihydroxy derivative of each aflatoxin. The test is sensitive and simple and gives no side reactions. The test is also applicable to aflatoxins G1 and G2.