Inhibition of Undesirable Gas Production in Tofu

Of 100 gas-producing bacterial isolates, 65% were Gram-negative. Bacterial growth and gas production in commercial tofu was accompanied by acidification, and pH decreases as low as 5.2. Coliform bacteria constituted 15% of the total bacterial flora. Sporeformers and yeast counts remained < 10³ CFU/mL. Pasteurization was effective in lowering the bacterial counts, and retarded gas production. The addition of lactic acid (reducing pH to 5.5) or lactic acid bacteria (2 × 10⁷ CFU/g) to tofu helped reduce gas production by about 50%. Addition of both lactic acid and Lactobacillus plantarum stopped gas production in contaminated tofu.     

EFFECT OF PENCILLIN ON FREE OR IMMOBILIZED LACTOCOCCI: MILK ACIDIFICATION AND RESIDUAL ANTIBIOTIC LEVEL

Five lactic acid cultures were added to milk containing penicillin, and the effect of immobilization on acidification and residual penicillin concentration were determined. Cells of Lactococcus lactis subsp . cremoris CRA-1 immobilized in calcium alginate beads were less sensitive to penicillin than free cells, and inhibition occurred later in the fermentation. The lactococci were less sensitive to penicillin when high cell densities were inoculated (10⁹ CFU/mL). There was a significant reduction of penicillin (up to 0.3 IU/mL) when milk was inoculated with high populations of Lac. cremoris and incubated at 30C for 6 h. The drop in penicillin concentration was not related to adsorption to the alginate or to the presence of β-lactamase on the cultures. When free cells of Lac. cremoris, Streptococcus salivarius subsp . thermophilus or Lactobacillus delbrueckii subsp . bulgaricus were added to milk containing antibiotics, and incubated at 4 or 10C for 48 h, significant reduction of penicillin levels did not occur in the contaminated milk. Milks containing more than 4 × 10⁶ lactococci CFU/mL can give false positive results in the antibiotic disk assay using Bacillus subtilis.     

植物生长建模与可视化——回顾与展望

回顾了植物生长的建模与可视化研究.为了加深对不同模型的目的、内涵与局限性的 理解,该文对植物生长模型进行了分类.在植物生长机研究中,对目前常见的分形方法、随机过 程、人工智能等建模方法的特点进行了比较分析.分别介绍了植物仿真与可视化方面的研究进 展及其相关技术,以及植物生长软件的发展状况.最后,总结了该领域研究中存在的主要问题, 并讨论了未来研究与应用方面的发展趋向及其前景.     

Maple Syrup as Carbohydrate Source in Dry Sausage Fermentation

Maple syrup was substituted for the glucose-sucrose component of a standard dry sausage formulation to assess its feasibility in fermented meat product manufacture. Sausage batters containing either type carbohydrate were inoculated with a mixed starter culture containing Lactobacillus plantarum, Pediococcus acidilactici and Micrococcus varians. Similar acidification patterns were observed in fermenting batters containing glucose-sucrose mixtures or maple syrup, and processing yields were unaffected by carbohydrate type. However, instrumental texture measurements (shear and compression forces) revealed that sausage made with maple syrup was significantly firmer than the standard product (P≤0.05). Maple syrup could be used in the manufacture of novel fermented meat products.     

Mechanical Properties of Hot-Pressed B-B4C Materials

Elastic modulus and flexural strength were measured at room temperature for solid pieces hot-pressed at 1900 to 2600 K from mixtures of B₄C powder and ≤15 wt% B powder. Regression analysis showed that elastic modulus and flexural strength are not significantly affected by these boron additions. Elastic modulus is related to porosity and flexural strength to porosity and grain size. The fracture surface energy of boron carbide was evaluated. X-ray diffraction and chemical analyses showed that the specimens were composed entirely of boron carbide after hot-pressing. Lattice constants increased with the initial boron content.     

Stability of Ethanol-Extracted Brown Rice to Hydrolytic and Oxidative Deterioration

Brown rice kernels extracted with EtOH at 7°C for 60 min were the most stable to lipolytic hydrolysis; free fatty acids (FFA) level in these kernels increased from 1.0–1.4% during 6 mo storage at 36°C. At lower extraction temperatures and times, kernels were less stable to lipolytic hydrolysis. The higher the temperature of extraction, the more susceptible kernels were to oxidative deterioration during storage; extraction time was not a factor. Kernels extracted with recycled EtOH were no more susceptible to oxidation than those extracted with fresh EtOH.     

Production of Ascorbate Free Radicals in Infant Formulas and Other Media

The effects of pH on ascorbate free radical production in ascorbic acid-supplemented cow's milk, soy- and milk-based infant formulas and in aqueous ascorbic acid solutions were examined. Formula and milk components decreased ascorbate free radical concentrations. Ascorbate free radical levels in pepsin-hydrolyzed soy and milk formulas were no different from those of unhydrolyzed formulas. At the phytate: iron molar ratio in the formulas, phytate decreased ascorbate free radical levels in pH 2.0 and 7.0 ascorbic acid solutions containing iron by about 35% and 50%, respectively. This antioxidant effect of phytate was not observed in soy-based and phytate-spiked milk-based formulas.     

Effects of pH on Calcium, Zinc, and Phytate Solubilities and Complexes Following In Vitro Digestions of Soy Protein Isolate

High intraluminal gastric pH values in young infants could affect the bioavailability of zinc in soy protein isolate formula. This investigation examined the effects of pH on the solubilities and complexes of calcium, zinc and phytate following in vitro pepsin and pepsin-pan-creatin digestions of soy protein isolate. The results of these in vitro studies suggested that (1) high intraluminal gastric pH values could lead to the formation of insoluble calcium-zinc-phytate complexes in the stomach following ingestion of soy protein isolate and (2) high intraluminal gastric pH values would only affect resultant soy zinc solubility in the small intestine in the absence of exogenous calcium or zinc but not in the presence of same.     

Chemical Treatment and Process Modification for Producing Improved Quick-Cooking Rice

Quick-cooking rice was produced by soaking raw, white, long grain rice in a 1% aqueous sodium citrate and calcium chloride solution (50:50) at 50°C for 15 min. The soaked sample was cooked in an autoclave at 121°C for 3 min and freeze-dried to 20% moisture followed by convective air-drying to a final moisture of 12%. Nutrient analysis of the rice chemically treated and dried by a combination of both methods contained maximum amounts of thiamin (2.0 μg/g), niacin (27.4 μg/g), and iron (25.1 μg/g). The rehydrated sample, prepared by boiling the rice in water at 100°C for 5 min, received high sensory scores.