TEXTURAL PARAMETERS IN COMPRESSION TESTING OF A GEL MADE FROM FRESH AND FROZEN FISH MINCE

The relation between deformability modulus and yield stress is evaluated in compression testing of a model product made from fresh and frozen stored mince of cod. The experiments were performed with a compression rate of 120 mm/min. Preliminary experiments showed decreasing values of yield stress when compression rates were below 50 mm/min. Two moduli were calculated from the slope of the compression curve; α₁, initially (small deformations) and α₂ in a linear part of the curve shortly before rupture of the gel. α₂ was linearly related to yield stress in gels of different water content, and in gels made from fresh and frozen raw material. α₁ showed different relations to yield stress depending on quality of the raw material.     

EFFECT OF SMOKEHOUSE TEMPERATURE, HUMIDITY AND AIR VELOCITY ON RATE OF HEATING AND QUALITY OF FRANKFURTERS

The effects of air velocity, relative humidity, temperature and presence of glucono delta lactone (GDL) on the quality of frankfurters, were evaluated. Rate of heating was inversely proportional to rate of weight loss during processing. High humidity processes at slow air flows had the fastest heating rates; however, quality was unacceptable because of fat separation and pale color. A process where the smokehouse temperature was slowly increased by 6°C increments, and where a low relative humidity and high air flow were used, gave the best quality. Color and texture was more desirable on products having higher shrink. The presence of GDL had no effect on the final color of products processed under the same conditions; however, maximum color appeared to develop earlier in samples containing GDL.     

EFFECT OF TIME AND FISH TEMPERATURE ON THE BLUNTING RATE OF FILLETING KNIVES1

The blunting rate of the disc knives in the filleting process is influenced by the anatomical location of the cut, cutting time and temperature of the fish body. The head cutting, abdominal-bone cutting and spinal bone separating knives blunt faster due to the structural differentiation in the fish body. The longer cut at the spinal bone separation also increases the blunting rate. Lowering the fish temperature from 285°K to 258°K (+12 to -15° C) accelerated the blunting rate of the knives about 2.4 times.     

DETERMINATION OF PARAFFIN WAX AND MINERAL OIL ON FRESH FRUITS AND VEGETABLES BY HIGH TEMPERATURE GAS CHROMATOGRAPHY

Paraffin wax and mineral oil coatings were determined on a large number of domestic and imported fruits and vegetables by high-temperature gas chromatography employing a Dexil 300 liquid phase with temperature programming up to 400°C. The surface coatings were removed from the foods by repeated dipping in chloroform. The chloroform extracts were concentrated and analyzed directly by gas chromatography. Identification of the waxes was made by comparison to known paraffin or mineral oil standards. Paraffin wax or mineral oil were found on squash, turnip, cucumber, sweet potatoes, egg plant, and most citrus fruits.     

LIPID OXIDATION OF FISH LIVER OIL AS AFFECTED BY LIGHT, ANTIOXIDANTS AND TEMPERATURE

Crude and refined Mackerel liver oil with or without antioxidants were stored in artificial light or in darkness to assess the effects of photo-oxidative stress on the stability of oils and the antioxidant activity of butylated hydroxy-anisole (BHA) and tert-butylhydroquinone (TBHQ) on those oils. Changes in peroxide value (PV) and thiobarbituric acid value (TBA) were monitored over 18 days at 5C and 40C. The results showed that visible light exposure played the most critical role in the acceleration of fish liver oil oxidation. The addition of antioxidants showed a significant effect in retarding oxidation with TBHQ more effective than BHA. The oxidation rate of the oils decreased in the following order: control with light > control + BHA with light > control without light > control + TBHQ with light > control + BHA without light > control + TBHQ without light. Higher PV and TBA values were observed in refined oils versus crude oils. Increasing storage temperature accelerated the oxidation of only refined oils in light.     

PROLONGING THE SHELF-LIFE OF FRESH GREEN CHILE PEPPERS THROUGH MODIFIED ATMOSPHERE PACKAGING AND LOW TEMPERATURE STORAGE

The postharvest quality of green chile fruit was compared after storage in 3 types of packages at 2 temperatures (24C and 8C). Package types were corrugated cardboard boxes, pressed cardboard trays overwrapped with VF-71 polyethylene, or low-density polyethylene (LDPE) bags. Fruit packaged in boxes or overwrapped trays had 24.8% and 10.1% weight loss, respectively, after 1 week of storage at 24C. Fruit packaged in polyethylene bags lost 0.3% weight and remained green. After 1 week at 8C, the weight losses were 3.8%, 1.8% and 0% for the boxed, overwrapped and bagged treatments, respectively. Postharvest quality was maintained up to 4 weeks when fruit were packaged in LDPE bags and stored at 8C. In a second study, steady state O₂ and CO₂ levels were determined inside the LDPE packages as fruit weight and temperature were varied. Storage temperatures were 24C, 16C and 8C. At 8C, steady state O₂ levels ranged from 12.0 kPa to 0.9 kPa, and CO₂ levels ranged from 2.0 kPa to 4.6 kPa as fruit weight was increased from 120 to 480 g. At 24C and 16C, fruit packaged in 480 g units had slower ripening rates than fruit packaged in smaller units; however, fruit stored at 8C remained green the longest, regardless of fruit weight.     

冷藏鲜肉中腐败乳酸菌的分离及鉴定

利用稀释平板法从冷藏3 d的肉样品中共分离出60株疑似乳酸菌菌株,经过2次划线分离,然后进行革兰氏染色、镜栓、过氧化氢酶试验、明胶液化试验、硝酸盐还原试验和H2S检验,得到36株乳酸菌.将分离出的这36株乳酸菌,经过形态学和生理生化鉴定,确定他们属于5大类,即清酒乳杆菌,13株;马里乳杆菌,8株;消化乳杆菌,7株;口乳杆菌,4株;未知乳杆菌,4株.