CHANGES IN SIZE OF GAS CELLS IN DOUGH AND BREAD DURING BREADMAKING AND CALCULATION OF CRITICAL SIZE OF GAS CELLS THAT EXPAND

Microscopic observation showed that a group of small air cells entrained during the early stage of mixing is the original cause of cell structure of bread. At the beginning of fermentation, about 3 × 10⁸/m² gas cells with diameters between 3 × 10⁻⁶ and 8 × 10⁻⁴ m were entrained in the dough. The distribution curve of cell size was approximately normal on a logarithmic scale. During fermentation and proofing, a great portion of carbon dioxide was released into cells larger than about 10⁻⁴ m in diameter that was equivalent to a few percentages of total number of gas cells. After baking, gas cells smaller than 10⁻⁴ m in diameter were not observed and the total number of cells in baked bread reduced to about 10⁶/m² with diameters between 10⁻⁴ and about 5 × 10⁻³ m. The critical cell size to expand generally agreed with the calculated value using an equation, rc'= 3s/E (re': critical radius to expand, s: surface tension, E: elasticity), and cited value of s and E.     

RELEASE OF ENTEROTOXIN A AND THERMONUCLEASE FROM GROWING AND NON-GROWING CELLS OF STAPHYLOCOCCUS AUREUS

Enterotoxin A and thermonuclease were produced by Staphylococcus aureus cell populations in all growth phases. Synthesis of entero-toxin was more rapid than that of thermonuclease early in the exponential phase, whereas later in the exponential phase the thermonuclease synthesis was more rapid than that of enterotoxin. The optimum temperature for enterotoxin production was 42°C, while that for thermonuclease production was in the range 27–33°C. Small amounts of enterotoxin and thermonuclease were released at temperatures up to 45°C.
During heat treatment of staphylococcal cells, enterotoxin production was not observed at temperatures in excess of those permitting growth, although small amounts of thermonuclease were produced. Intracellular enterotoxin was not detected after disintegration of cells under pressure at –30°C. Enterotoxin at detectable concentration, was not bound to the cell membranes. All the results obtained indicate that the synthesis of enterotoxin by S. aureus is intimately associated with cell growth.     

银耳多糖的保健作用及应用前景

综述银耳中的功能性成分银耳多糖的保健作用及银耳多糖的种类、提取方法,探究银耳多糖的价值,为食用菌类食品的开发应用提供科学依据,并同时介绍它在功能性食品中的开发应用前景.     

ENRICHMENT OF SEVERELY AND MODERATELY HEAT-INJURED LISTERIA MONOCYTOGENES CELLS

Recovery of injured cells of a 90% heat kill of Listeria monocytogenes strain Lm82 in Trypticase soy yeast extract broth (TSBYE) at 30C was determined in enrichment broth and modified enrichment broth. Although the surviving population was heterogeneous with respect to degree of damage, two fractions of surviving cells defined as moderately and severely damaged were considered. Progeny of moderately damaged survivors (NaCl-sensitive but not enrichment medium-sensitive) increased about 100-fold in 5 h; severely damaged cells (enrichment medium- and NaCl-sensitive) did not grow in this time period. Most of the severely damaged cells required 20 h or longer to recover in TSBYE and even longer in TSBYE plus selective agents. Recovery was accelerated either by adding sodium pyruvate or by reducing the oxygen level. The results were used to design a Mark I preenrichment/enrichment protocol based on the U.S. Food and Drug Administration's selective enrichment broth.     

EFFECTS OF TYPES AND LEVELS OF FAT AND RATES AND TEMPERATURES OF COMMINUTION ON THE PROCESSING AND CHARACTERISTICS OF FRANKFURTERS

ABSTRACT— Frankfurter emulsions containing either 25% or 35% beef fat, pork fat, or cottonseed oil were prepared by comminuting at 1500, 2500, or 5000 rpm to temperatures ranging from 45°–85°F. Data were obtained on the viscosities of the emulsions; except for initially high viscosities for which unmelted fat was responsible, the viscosities of emulsions containing the fats, or oil, were similar: viscosities tended to decrease with increasing time and temperature of chopping. The frankfurters were stuffed, smoked, and cooked, and data were obtained on shrinkage, fat retention, ease of peeling, specific gravity, and texture. Shrinkage was inversely related to content of fat. Fat separation mainly occurred in processing frankfurters containing beef fat; the data suggest that emulsions containing beef fat should be comminuted to 65°–75°F to avoid possible under or overchopping: the results show that optimum conditions were time as well as temperature dependent. The air content of frankfurters varied inversely with the maximum temperature attained during communition. Frankfurter skin strength was lessened on increasing the temperatures to which emulsions were communited; elasticity, the equivalent of rubberiness, decreased under these conditions.     

EFFECTS OF PROCESSING AND SQUALENE ON COMPOSITION AND OXIDATIVE STABILITY OF SEAL BLUBBER OIL

Effects of processing on constituents of seal blubber oil and that of squalene on oxidative stability of several oils were monitored. The content of α-tocopherol in oil decreased during processing, especially at the bleaching and deodorization steps. There was also a concurrent reduction in the contents of squalene and free fatty acids, especially during deodorization. Oils treated with squalene did not show any improved oxidative stability and in some cases were even less stable.     

EFFECTS OF GAMMA IRRADIATION OF BARLEY AND MALT ON MALTING QUALITY

Two two-rowed barley cultivars, Tokak and Clerine, were irradiated at two different dose ranges (0.05–0.75 kGy and 0.5–5.0 kGy) using a ⁶⁰Co source. Irradiation of barley at the medium levels before malting had detrimental effects on most of the malt quality criteria. The detrimental effects of irradiation was lower at doses up to 0.25 kGy. Irradiation of malt samples caused either slight or no deterioration of quality characteristics .     

INHIBITION OF LIPOXYGENASE AND BLOOD THINNING EFFECTS OF MACKEREL PROTEIN HYDROLYSATE

Mackerel (Scomber australasicus) muscle was homogenized with deionized water at a ratio of 35:70 (w/w) for 2 min, boiled for 10 mm, and then cooled. Protease N was added to hydrofyze the homogenate at 50C for 2 h, then heated at 90C for 10 mm to stop the reaction. The supernatant obtained after centrifugation and filtration was the mackerel protein hydrolysate (MPH), It showed inhibitory effects on both lipoxygenase (LOX)‐catalyzed ami hemoglobin (Hb)‐catalyzed oxidation of arachidonic acid and linoleic add. Similar inhibitory effects were found on LOX's of soybean, tilapia gill and grey mullet gill. Blood thinning effects were observed in‐vitro by mixing MPH with red blood cells. The addition of MPH resulted in a reduced fluid consistency from 0.03 to 0.02, and an increased flow behavior index from 0.67 to 0.87 indicative of a flow behavior becoming closer to Newtonian type and a thinning consistency.