EFFECTS OF LONG-TERM STORAGE OF FOODS ON QUALITY OF PROCESSED FOODS II.

The effects of long-term storage at 4.4, 21.1, and 37.8°C on physicochemical characteristics, nutritional and organoleptic qualities of freeze-dehydrated ration items from Packet Long Range Patrol were studied. The items included beef hash, beef stew, chicken stew, spaghetti with meat sauce, chili con carne with beans, chicken and rice, pork with escalloped potato, and beef and rice. The freeze-dehy drated foods were stable in quality during storage at 4.4, 21.1, and 37.8°C. After 44 months of storage all freeze-dehy drated ration items were in acceptable condition.     

LONG-TERM STORAGE OF ASEPTICALLY PROCESSED AND PACKAGED DAIRY FLUIDS1

Aseptically processed and packaged dairy fluids were investigated for stability during long-term storage. Model solutions of whey and sodium caseinates, and combinations of them with milk fat were used. Sedimentation in whey protein solutions was extensive. No significant sedimentation was observed in casein solutions even after 500 days of storage. Addition of milk fat retarded sedimentation in whey protein solutions initially. Very little fat separation was observed in whey-fat solutions. Larger amounts of fat separation were observed in casein-fat or casein-whey-fat solutions. Casein-whey-fat sediments were in the form of a gel. Sporadic gelation was observed in casein solutions. Sedimentation rates from cheese whey alone are similar to gelation rates for milk for similar thermal treatments. Reactivated enzymes may be responsible for both phenomena.     

STORAGE QUALITY OF MINIMALLY PROCESSED CABBAGE PACKAGED IN PLASTIC FILMS

The effects of packaging and storage at 3C in a refrigerated case on quality changes of minimally processed cabbage were studied. Shredded cabbage samples were packaged in three forms: bags of monooriented polypropylene film (OPP bags) and polyethylene trays overwrapped with a multilayer polyolefin (RD106-PE tray) or with a plasticized PVC film (PVC-PE tray). All types of package effectively controlled the weight loss. The modified atmosphere in PVC-and RD106- PE trays did not change more than 3% as compared with normal atmosphere levels. However, in OPP bags, O₂ reached 2% and CO₂ increased to approximately 13% after 3 days. The microbiological quality during the storage period for all types of packaging was satisfactory. OPP samples were significantly better (p <0.05) in general appearance, wilting and browning but developed an off-odor. No off-odor was detected in samples packaged in PVC and RD106-PE trays. Shelf life for the three packaging forms was estimated.     

EFFECTS OF SOY PROTEIN ISOLATES ON QUALITY OF CHOCOLATES DURING STORAGE

The effect of soy protein isolate (SPI) on oxidation rate, changes in color and hardness, and microbiological aspect of chocolates during storage were studied. The Peroxide Value (PV) of the control and 5% showed SPI were highest in week 3 and decreased at the following week, while 10% SPI showed the lowest PV in week 10 as compared to the others. The Anisidine Value (AV) of all chocolates showed an increasing pattern during 10 weeks of storage. The Total Oxidation Value (TV) of all chocolates was found to be highest at week 3 and lowest at week 10 when 10% SPI was used. During storage, all chocolates slightly increased in hardness and turned darker in color. The Total Plate Count (TPC) of the control and SPI chocolates was less than 1,000 colonies/g.     

EFFECTS OF PASTEURIZATION OR SODIUM BENZOATE ON LONG-TERM STORAGE STABILITY OF PEACH PUREE

The effect of long-term storage on the stability of pasteurized (PA) or sodium benzoate (SB) (0.1%) treated peach puree was studied. Color, viscosity, soluble solids, pH, titratable acidity, sugars and organic acids were monitored over 4 months. Yeasts were the major microorganisms causing spoilage in nontreated peach puree. Storage at 2C increased the holding time of the control to 17 days compared with 3 days at 25C. No yeast or other microorganisms were found in PA or SB treated puree held at 2 and 25C, for 120 days; the most significant change observed was a gradual browning. Cold temperature storage slowed down the browning. Other compositional changes were minimal. Pasterurized or SB puree stored at 25C for 4 months showed a decrease in sucrose and an increase of glucose and fructose. Malic, citric and quinic acids were stabilized by SB. Pasteurization or use of SB may be valuable for holding partially processed peach puree.     

RHEOLOGICAL BEHAVIOR OF PROCESSED MUSTARD. II. STORAGE EFFECTS

Samples of processed yellow mustard with three different particle size distributions (slightly-coarse, standard, and fine) were prepared according to a standard formulation and pilot-plant replication of the commercial methodology and stored for 3 months at 5°C, 25°C, and 45°C. After 3-month storage at 45°C, all samples showed visible liquid separation (syneresis) and aggregation of colloidal particles, as indicated by increase in d _pop and decrease in % colloids. The fine milled samples exhibited syneresis and an increase in d _pop after 3-month storage even at 25°C. The bimodal distribution did not show significant changes as a result of aggregation. In general, increase in d _pop increased apparent viscosity (η _ap ), flow behavior index (n) from the Herschel-Bulkley model, and exponent n" from the loss modulus (G") power law equation. As d _pop increased, Bingham yield stress _o), plastic apparent viscosity (η _p ), shear stress constant (A) from the Weltman stress decay model, yield stress (_o) and consistency index (m) from the Herschel-Bulkley model, exponent n' from the storage modulus (G') power law equation, and minimum values of loss tangent (tan δ) decreased. In heterodisperse semi-solid foods such as processed mustard, the particle size distribution influences the structure (i.e., packing) and the rheological behavior. Therefore, time and temperature dependent instabilities such as syneresis may be minimized by controlling particle size distribution during processing.     

CONTROLLED ATMOSPHERE STORAGE AND EDIBLE COATING EFFECTS ON STORAGE LIFE AND QUALITY OF TOMATOES

Tomatoes at pink stage maturities were coated with Semperfresh^TM edible fruit coating which is composed of sucrose esters of fatty acids, sodium carboxymethyl cellulose and mono-diglycerides of fatty acids. One group of coated and uncoated tomatoes were stored at 23 × 2C under air atmosphere, another group was stored at 12C under air atmosphere and third group was stored at 12C, 93–95% RH in a controlled atmosphere (CA) containing 3% CO₂, 3% O₂ and 94% N₂. Samples of tomatoes were analyzed for firmness, weight loss, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene to examine changes in quality during storage. Semperfresh^TM edible fruit coating was found to be significantly effective at both storage temperatures (23 × 2C and 12C) in air to delay changes in firmness, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene. Semperfresh^TM fruit coating reduced fruit weight loss as compared to fruit without coating but the difference between coated and uncoated tomatoes was not significant. Shelf-life of pink tomatoes was increased 3 days at 23 × 2C and 6 days at 12C in air by coating. CA storage delayed compositional changes in tomatoes significantly as compared to air storage of coated and uncoated tomatoes. CA storage also had a significant potential for reducing weight loss and microbial spoilage. Tomatoes were stored 40 days in CA. Coated and uncoated tomatoes exhibited the same results in CA.     

采收期对金红苹果贮藏品质的影响

以金红苹果为试材,研究不同采收期对金红苹果贮藏品质的影响,为金红苹果贮藏保鲜提供理论和实践依据.研究结果表明:在吉林地区,金红苹果适宜的采收期为8月末9月初.此期,果实的硬度约为11.00kg/cm2,可溶性固形物含量约为12.40%,可滴定酸含量约为0.76%.果实冷藏100d后,仍能保持硬度达7.90 kg/cm2,可溶性固形物含量约为11.30%,可滴定酸含量达0.50%,失重率4.70%,而且果实外观新鲜,腐烂率仅为0.50%.     

花粉多糖对酸奶贮藏中酸度及感官品质的影响

以牛乳为原料进行发酵,并添加花粉多糖研制多糖酸奶.测定贮藏期间对酸奶的酸度,色泽、气味、滋味和组织状态等感官指标进行评定,研究多糖对酸奶酸度和感官品质的影响.结果表明.多糖可抑制酸度上升,延迟酸奶的后酸化过程.多糖在酸度上可延长酸奶贮藏期5 d～6 d.     

HALOTHANE-GENOTYPE AND DURATION OF REFRIGERATED STORAGE EFFECTS ON THE QUALITY OF VACUUM-PACKAGED PORK LOINS

Loins (n=72) from halothane negative (NN) and carrier (Nn) pigs were vacuum-packaged and stored for 0, 3, or 6 weeks at 2C. Samples from Nn pigs had more (P<0.001) purge loss than NN-loins after 3 and 6 weeks of storage. Color scores for chops of Nn pigs were lower (P<0.001) than for the NN animals after 0 and 3 weeks; but after 6 weeks of storage, chops from Nn and NN pigs received similar American color scores. Chops from Nn pigs were lighter (P<0.001) and less (P<0.001) red than chops from the NN animals; however, L* values of chops from Nn pigs decreased, and a* values increased, from 0 to 3 weeks of storage. Although initial quality traits of chops from Nn pigs were inferior to those of NN, pork color of Nn-pigs appeared to be improved with extended storage.     

EFFECT OF TEMPERATURE ON THE QUALITY OF MUSCLE FOODS

Heating/cooking alters a food's flavor precursors yielding a product with a new pleasing taste. While heating to a high temperature destroys most pathogens thereby enhancing safety, it also alters the food's flavor by changing the precursors and final flavor components of the food. For example, heating meat to above 77C not only destroys many foodborne pathogens but also causes major changes in level of desirable flavor precursors. Many of these changes are due to alteration in activity of endogenous hydrolytic enzymes as well as heatinduced structural and functional changes. Heating induces differential production and distribution of flavor principles and flavor precursors. A secondary effect of temperature on food-flavor is its direct affect on analysis of flavor volatiles, i.e., high purge temperatures bias analysis of flavor components by production of new and destruction of existing components. This paper focuses on the structure/function relationship of meat proteins and their proteolytic products as they relate to meat flavor and end-point cooking temperature. The paper also will address the effect of analytical temperature on meat flavor analysis.     

EFFECT OF STORAGE ON THE RHEOLOGICAL BEHAVIOUR OF BABY FOODS

The effect of storage temperature on rheological behaviour of four varieties of baby foods was studied. After 24-month storage at 15C and 25C, the constant A in Weltman model increased significantly for the vegetables, meat and fish samples, and decreased significantly for the fruit samples. After 24-month storage at 5C and 15C there were no significant changes in flow behavior index, consistency index and yield stress of the Herschel-Bulkley model for the vegetables, meat, fish and fruit samples. Increase in storage temperature decreased the consistency index and yield stress of the fruit samples.     

海藻糖和水分活度对腌制海鳗保藏性能的影响

为考察海藻糖和水分活度对腌鱼保藏的影响,以挥发性盐基氮、三甲胺、细菌总数、酸度和氧化值等为指标采用光度分析方法.结果表明腌制海鳗在水分活度0.8,腌鱼中含海藻糖2%时,腌鱼保藏性能和感官品质最佳.结论:海藻糖具有明显的保鲜作用,控制水分活度是品质关键.     

EFFECTS OF VISCOSITY OF LIQUID FOODS ON PALATAL PRESSURE

The deglutition of non-Newtonian liquids introduced into the mouth was studied dynamically by measuring palatal pressure (P) with pressure transducers set at three locations on the palate. The value of P and the swallowing pressure (S) changed only from 100 to 200 g/cm² over the viscosity range 10⁻² to 10¹ Pa.s. The retaining time (T) and work (W), required for swallowing after the liquid entered the mouth, remained almost constant up to a critical value of 1.0 Pa.s. above which both T and W increased markedly. When the viscosity was low, all of the liquid was swallowed in one deglutition, up to 15 mL volume. Therefore, T was almost constant but S increased with the volume. When the viscosity was high, the liquid was swallowed in several smaller portions. When the volume was high, T increased and S was either constant or it decreased.