ABSORPTION OF VOLATILE METHYL KETONES BY A NATURAL MODEL SYSTEM: FREEZE-DRIED CREAM

A technique was pursued for the enrichment of a dried model system by exposure of the system to an atmosphere of volatile flavor compounds. As the exposure time was lengthened, the quantity of each of the flavor compounds absorbed by the freeze-dried cream increased. Short chain methyl ketones were absorbed by the dehydrated cream in larger amounts than those determined for the higher molecular weight homologs. In these experiments the desorption, during frozen storage, of highly volatile ketones from freeze-dried cream exposed to 2-alkanones was greater than that obtained for the high molecular weight homologs. To compensate for the loss of highly volatile flavor constituents during prolonged storage, a dried food product could be enriched above the normal level. Following storage, residual levels of such volatiles would more closely approximate the initial concentration in the food. The application of these findings to a commercial absorption process could be of value in improving the flavor and odor characteristics of a dehydrated food, or in the fabrication of completely new synthetic foods or food analogs.     

咨询活动效益综合评价模型研究

建立了综合评价指标体系；运用直接和间接量化方法，对难以客观评价的在社会上产生的经济效益和社会效益进行了量化；使用层次分析法，确定了各指标和各分指标的权重；采用区间值抽样调查方法，给出了各指标和各分指标的参考值；利用Ｆｕｚｙ综合评判思想，对评价总得分的计算和咨询机构的定级给出一种较理想的方法．     

EFFECT OF FRANKFURTER CURE INGREDIENTS ON N-NITROSODIMETHYLAMINE FORMATION IN A MODEL SYSTEM

The effect of cure ingredients on the nitrosation of dimethylamine was investigated in a model system containing sodium nitrite. The ingredients used were: sodium chloride, sodium nitrate, glucono-δ-lactone (GDL), sodium acid pyrophosphate (SAPP), sodium erythorbate (NaEry), sodium ascorbate (NaAsc), ascorbic acid (AscH) and sodium tripolyphosphate (STPP). Under conditions approximating those used in the processing of frankfurters, CDL by itself was found to increase the formation of dimethylnitrosamine (DMNA), whereas reductants reduced the amount formed. Of the reductants, NaAsc or NaEry, in combination with other cure ingredients have similar inhibitory activity. The use of NaCl, NaNO₃ and SAPP had little or no effect on DMNA formation.     

INHIBITION OF AEROBIC AND ANAEROBIC GROWTH OF STAPHYLOCOCCUS AUREUS IN A MODEL SAUSAGE SYSTEM

Sodium nitrite, potassium sorbate, and glycerol monolaurate all inhibited anaerobic growth of Staphylococcus aureus more than its aerobic growth in an agar-meat model sausage system, and all were more inhibitory when lactic acid was added. Whereas anaerobic growth of S. aureus was inhibited by concentrations of 100, 2500, and 2500 ppm, respectively, of nitrite, potassium sorbate, and glycerol monolaurate, corresponding concentrations of 150, 5000, and 5000 ppm were required to inhibit aerobic growth ((20 meq lactic acid added).
Sorbic acid, a 3:1 mixture of sorbic acid and glycerol monolaurate by weight, and butylated hydroxyanisole (BHA), however, did not show differential inhibitory effects toward aerobic and anaerobic growth of S. aureus and also were more effective inhibitors with addition of lactic acid. Sorbic acid suppressed staphylococcal growth in the model sausage system at 500 ppm, the mixture of sorbic acid and glycerol monolaurate at 750 ppm, and BHA at 10,000 ppm (20 meq lactic acid added).     

SYNERGISTIC ACTIVITY OF CAPELIN PROTEIN HYDROLYSATES WITH SYNTHETIC ANTIOXIDANTS IN A MODEL SYSTEM

Capelin protein hydrolysates (CPHs) were examined in a β-carotene-linoleate model system together with synthetic antioxidants, namely butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tert-butyl hydroquinone (TBHQ). Addition of CPHs was at 0.25 and 1 mg per 5 mL in the above emulsion. BHA and BHT were added at levels of 2.5 and 5 μg and TBHQ at 5 and 10 μg. Absorbance of model emulsion system at 470 nm was recorded every 30 min for 2 h. CHPs and synthetic antioxidants inhibited oxidation of linoleic acid effectively. In the experiment with BHA, the influence of CPHs was significant (p<0.01) for the samples incubated for 60, 90, and 120 min; and in experiments with BHT and TBHQ during the entire incubation period. The influence of added BHA and BHT on inhibition of bleaching of β-carotene in the emulsion system was significant (p <0.01) during the incubation period and after 60, 90 and 120 min when TBHQ was used. A synergistic effect was observed only for CPHs and TBHQ when incubation time was 60, 90, and 120 min.     

EFFICIENCY OF ANACARDIC ACID AS PRESERVATIVE IN TOMATO PRODUCTS

Anacardic acid, 6[8'(Z), 11'(Z),14'-pentadecatrienyl] salicylic acid is the main active principle of Anacardium occidentale ( Anacardiceae ), the cashew. Cashew nut shell liquid (CNSL) contains approximately 70% anacardic acids, 18% cardol, 5% cardanol, and some other phenols and less polar substances. Because of the presence of anacardic acids, the CNSL exhibits potent antimicrobial activity. In view of this and the potent antimicrobial activity of anacardic acid observed in our previous study, the present study was planned to evaluate the anacardic acid isolated by us in our previous study as a food preservative. The effect of anacardic acid at 0.014% (w/w) was studied in tomato paste and tomato ketchup inoculated with 2  ×  10⁴ cfu/g of Staphylococcus aureus, Bacillus subtilis and Escherichia coli and stored at room temperature. Good activity was observed, as no viable growth after 28 days in both the products. Results showed that anacardic acid was active against both gram-positive and gram-negative bacteria. Results of the study indicated that anacardic acid can act as a potential preservative in tomato products and can be considered as an alternative natural preservative over the synthetic preservatives.

PRACTICAL APPLICATIONS

When safeties of synthetic preservatives are questioned, natural substances of plant origin may appeal to the public. The anacardic acid isolated form cashew nut shell is present in cashew nut, which is being consumed by a number of people as a food material. So it is relatively safe to use as an alternate to the existing synthetic preservatives.     

INHIBITION OF Staphylococcus Aureus IN A MODEL AGARMEAT SYSTEM BY MONOLAURIN: A RESEARCH NOTE

A sterile agar-meat was acidified with lactic acid and seeded with Staphylococcus aureus. Monolaurin (Lauricidin®), which is a GRAS emulsifier, caused both static and cidal effects on S. aureus 196E. When compared to potassium sorbate, Lauricidin® was slightly more active. The combination of sorbic acid and Lauricidin® (Lauribic™) gave a greater inhibitory effect than either of the substances alone. Inhibitory effects were greater on "anaerobic" than "aerobic" growth. These results indicate that monoglyceride emulsifiers like Lauricidin® alone or in combinations with other preservatives can be used in foods to create environments which are hostile to microorganisms.     

A KINETIC MODEL FOR ACCELERATED TESTS of MAILLARD BROWNING IN A LIQUID MODEL SYSTEM

The feasibility of a novel approach to accelerated storage tests was evaluated for Maillard browning of a glucose-glycine model system. This approach is based on use, in addition to external conditions such as temperature, of composition to accelerate the rate of deterioration. Reactant concentration, and catalysts are not affected by storage conditions but still can be used to obtain a high rate of deterioration. They can be, therefore, an important part of accelerated tests procedures provided that one establishes first the comprehensive kinetic model that includes the effect of all the factors that are used. For a glucose-glycine model system, a comprehensive kinetic model was evaluated for a wide range of conditions (reactants concentration 0.0625-2 M, copper ions up to 50 ppm, pH 4–8 and temperatures 30–61C) and found to have an apparent order of reaction of 0.8 (representing the combined effect of a first order induction period and the following zero order phase). All the factors that were used are capable of affecting the rate of reaction. the kinetic model was found to be a simple four parameter equation where the effect of the pH is manifested mainly through the level of the unprotonated form of the amino acid. However copper ions have a relatively small effect and thus could be eliminated from the model. Without the copper, the kinetic model is a very simple three parameter equation that can be easily evaluated by accelerated tests and used to extrapolate the data to normal storage conditions.     

COMPUTER SIMULATION OF VITAMIN DEGRADATION IN A DRY MODEL FOOD SYSTEM DURING STORAGE1

During storage of dry foods, oxidative mechanisms can result in nutrient degradation. Accurate prediction of the vitamin content for dry foods during storage is essential to provide the processor with the assurance of meeting label claims. Since appropriate shelf-life tests for measurement of vitamin degradation represents an alternative worth considering. A mathematical model of the relationship between the rate constant of ascorbic acid oxidation and water activity was established. Computer simulation to predict product moisture content and ascorbic acid degradation in a dry model food product was developed by considering the simultaneous influence of water activity and temperature on rate constants which change with storage time due to varying storage environments. The computer simulation predicts product moisture content and vitamin degradation in good agreement with the experimental data. The simulation will account for the influence of storage temperature and relative humidity as well as characteristics of the food product and package material.     

STATISTICAL EVALUATION OF ARRHENIUS MODEL AND ITS APPLICABILITY IN PREDICTION OF FOOD QUALITY LOSSES

To minimize quality losses occurring during processing and storage and to predict shelf-life, quantitative kinetic models, expressing the functional relationship between composition and environmental factors on food quality, are required. The applicability of these models is based on the accuracy of the model and its parameters. In this paper, the calculation of the Arrhenius parameters and the accuracy of the derived model were compared, using three statistical methods, namely: linear least squares, nonlinear least squares and weighted nonlinear least squares. Results indicated that the traditional two-step linear method, was the least accurate and the derived energy of activation and the pre-exponential factor had the largest confidence interval. The latter was shown to have a profound effect on the precision of the calculated rate constant and the predicted shelf life. Based on previous reports that indexes of deterioration