CHANGES IN THE ACTIVITY AND SUBCELLULAR DISTRIBUTION OF PPO IN 'DELICIOUS' APPLES DURING CONTROLLED ATMOSPHERE STORAGE

Polyphenol oxidase (PPO) activity in 4, 000 × g, 100, 000 × g, 200 × g and soluble fractions of ‘Delicious’ apples was monitored during 28 weeks of controlled atmosphere storage. PPO activity in 4, 000 × g and 100, 000 × g fractions decreased, while that in soluble and 200 × g fractions increased. These shifts in subcellular location occurred sooner in apples which were stored under high CO₂ conditions (2.5–6% O₂, 8–12% CO₂) than those under normal CA conditions (2% O₂, 3% CO₂). Polyacrylamide gel electrophoresis of 4, 000 × g fractions isolated from ‘Delicious’ apples at harvest showed 2 bands with PPO activity, while stored samples all had 3 bands. Isoenzyme patterns were found to vary in different subcellular fractions.     

FLAVOR VOLATILES OF SOME COOKED VEGETABLES

SUMMARY– Using previously described sampling techniques, the flavor volatiles of a number of cooked vegetables were collected and analyzed by gas chromatography. The vegetables investigated were Brussels sprouts, cauliflower and runner beans and, in addition to the fresh vegetables, some preserved samples were examined. Quantitative measurements were made of the individual flavor components and the results were compared with those for fresh cabbage.     

EFFECTS OF TEXTURAL CHANGES IN COOKED APPLES ON THE HUMAN BITE, AND INSTRUMENTAL TESTS

A multiple-point sheet sensor was used to measure the bite force applied to raw and cooked apple specimens during the first bite with incisors. Wedge penetration tests were compared with human bite measurements on the same samples. The shape of the force-time curves during biting of cooked apples clearly differed from that for raw apples. The first curve of cooked apple biting became jagged, and the maximum force was reduced. The second curve emerged following the first curve in most subjects as a characteristic feature of cooked apple biting, whereas it was not seen in the bite curve of a raw specimen or the wedge penetration curve of a cooked specimen. The maximum force for tissue fracture decreased for cooked apples, but the duration of biting increased. No adequate counterparts for the impulse of biting could be obtained from the load-displacement curves of the wedge penetration tests. The existence of parameters only measurable by bite tests and not by mechanical tests suggests the necessity of directly measuring the human bite.     

SENSORY QUALITY OF GALA APPLES AS INFLUENCED BY CONTROLLED AND REGULAR ATMOSPHERE STORAGE

The sensory quality of Gala apples stored for up to 4 months in delayed controlled atmosphere (CA), regular atmosphere (RA), and a combination of sequential CA and RA storage (CR) was evaluated. Sensory analysis included difference and acceptance testing. Firmness, soluble solids and titratable acidity contents, and volatile flavor profiles were measured analytically. Acceptability decreased with storage time. Apples stored in RA were more acceptable than apples stored in CA or CR; the differences between storage treatment were not significant after 4 months of storage. Firmness decreased with storage time, but was not affected by storage treatment. Soluble solids and titratable acidity contents were not affected by storage treatment or time. Storage treatment, storage time, and lot had a significant effect on the volatile flavor profiles. CA storage and extended storage contributed to decreases in the content of volatile flavor compounds.     

老抽香气成分GC-MS分析

用无水乙醚提取酱油中的香气成分,气相色谱--质谱联用(GE-MS)分离鉴定其化学组成,以面积归一化法测定其相对含量,老抽乙醚萃取物中共鉴定55种化合物,其中对老抽香气成分贡献最大的是3,8-二羟基-2-甲基色酮,糠醛,2呋喃醇,2-乙酰吡咯,香茅醇,2,6-二甲氧基苯酚,4-乙基-2-甲氧基苯酚(4-乙基愈创木酚).与文献报道的酱油香气成分有所不同,多种成分未见报道.     

SOME CHANGES IN BEER FLAVOUR DURING AGEING

Bottled beers were stored for 5–6 months at 0° C., 25° C. and 40° C. At the highest temperature, decreases in the concentrations of ethyl acetate and isoamyl acetate were found. Ethyl formate showed an increase in concentration, and the concentration of acetaldehyde increased at the beginning of storage, and decreased thereafter. At the lower temperatures the changes in concentrations of these compounds were considerably smaller; at 0° C. they were hardly detectable in most cases. Different beer types, fermented with the same yeast strain, behaved differently on ageing.     

FINITE ELEMENT ANALYSIS OF MODES OF VIBRATION IN APPLES

Three-dimensional finite element models were developed to study modes of vibration in apples. The apple models were created using two mathematical equations, in which the geometry of the apple was described by a four-parameter equation and the core structure by an exponential function. Modal analyses were performed to identify the vibrational modes and to study the effects of material properties, structure (i.e., the skin and core), shape, and size on them. There were three classes of vibrational modes in apples: torsional, spheroidal, and nonaxisymmetric. A majority of modes between 0 and 2000 Hz belonged to the nonaxisymmetric class. The square of natural frequency was linearly related to Young's modulus of the apple. The presence of apple skin could increase the natural frequency by 7% for torsional modes and less than 4% for spheroidal modes. As the elastic modulus of the core was doubled, the natural frequency increased by up to 7% for spheroidal modes and well below 1% for torsional modes. The natural frequency for the first mode of each class decreased by no more than 8% as Poisson's ratio was doubled. Apple shape had a large effect on the natural frequencies of all three mode classes; spheroidal modes, however, were less affected by apple shape. The natural frequencies decreased with increasing apple size, but use of the firmness index f²m^2/3, where f is the natural frequency and m is the mass of the apple, minimized the size effect.     

CHANGES IN SOME B-GROUP VITAMIN LEVELS IN FERMENTING CIDERS

The changes in level of thiamin, nicotinic acid, pantothenic acid and riboflavin were followed in fermenting high-nitrogen and low-nitrogen ciders by means of microbiological assays. The results found were compared with the changes found in a commercial cider fermentation.     

SOME PHYSICOCHEMlCAL PROPERTIES OF STARCHES AS AFFECTED BY CHANGES IN ATMOSPHERIC PRESSURE

The effects of varying atmospheric pressures on the properties of starches were investigated. Four types of starches-corn, rice, potato and wheat-were studied for their water-binding capacity and viscosity behavior. Photomicrographs of starch suspensions were taken at five altitudes and temperatures of 22 °, 60 °, 70 °, 80 ° and 90 °C respectively. Measurements of the photomicrographs showed corn, potato and rice starch granules to increase in size on changing elevation from sea level to 10,000 feet. Wheat starch was not affected. Water-binding capacity increased for corn and potato starches as the altitude increased, but rice and wheat starches were not affected. The viscosity of corn, rice and wheat starch suspensions decreased initially with increasing altitudes but increased at the higher altitudes. The viscosity of potato starch suspensions did not change at increased elevations.     

VARIETAL DEPENDENCE OF HOP FLAVOUR VOLATILES IN LAGER

A series of lagers brewed with single hop varieties was analysed via extraction and gas chromatography/mass spectrometry. Each hop variety contributed a small number of unique flavour compounds to the beers. Significant, reproducible differences were found between the concentrations of individual hop compounds and hop compound classes in the different beers.     

EFFECTS OF PROCESS VARIABLES ON RETENTION OF VOLATILES IN FREEZE-DRYING

SUMMARY— Retention of organic volatiles in freeze-dried solutions of mono-, di- end polysaccharides was studied as a function of different process conditions. Under the experimental conditions used, slow freezing and decreasing sample thickness promoted retention. The effects of platen temperature and of concentration of solution components were more complex. Effects of process variables were explained on the basis of a mechanism which postulates formation of microregions due to association of carbohydrate molecules. These microregions become impermeable to organic compounds when their water content decrease below a critical level.     

SENSORY CHARACTERISTICS OF CONTROLLED ATMOSPHERE- AND AIR-STORED ‘GALA’ APPLES1

‘Gala’ apples from two Summerland sites were harvested at two harvest dates for two growing seasons (1994, 1995) and stored for 6 months in air and controlled atmosphere (CA). At harvest maturity indices were recorded. After storage, flesh firmness, titratable acidity and soluble solids were determined and sensory attributes were evaluated by a trained sensory panel. In both years, analyses of variance showed apples picked at commercial harvest were significantly more crisp, firm, and sour and less fruity and sweet than apples harvested two weeks later. Apples stored for 6 months in CA were more crisp, firm, juicy and sour, had fewer off-flavors, and had greater overall acceptability than apples stored in air. Apples held at 1.2% O₂for 6 months were more crisp than apples stored at either 2.5% O₂ or 5% Q, while apples stored at 5.0% O were significantly less firm, juicy, and sour than apples stored using the other O₂ concentrations. Apples stored at either 1.2% and 2.5% O₂ had significantly more fruity flavor than apples stored at either 5.0% O₂ or in air.     

MODELING THE SENSORY QUALITIES OF PROCESSED APPLES AFTER CONTROLLED ATMOSPHERE STORAGE AND FROZEN STORAGE1

Durational effects of controlled atmosphere storage (CA) and frozen storage on apple quality were studied for commercially processed pies made from Northern Spy, Idared and Nova Spy apples. Sensory tests on apple pie quality indicated that the duration of apples in CA significantly affected the quality of the processed apple. Extending the CA duration of the apples to 45 weeks resulted in a pie filling with reduced apple flavor, tartness and astringency, and with increased sweetness and off‐flavor. To minimize flavor/taste changes throughout the processing season, close attention must be given to the product's sugar/acid formulation: by week 27 for Idared apples and by week 33 for Northern Spy and Novaspy apples. The texture and appearance of processed Novaspy and Idared fruits were affected earlier in CA than Northern Spy apples. The frozen product was relatively stable for all three varieties, especially for apples processed early in the storage season (15–27 weeks). A strategy that utilizes short‐ to medium‐term CA with longer‐term frozen storage would optimize quality across the season.     

QUALITY CHANGES OF FRESH-CUT HONEYDEW MELONS DURING CONTROLLED ATMOSPHERE STORAGE

Quality, physiology, and microbial population were monitored with honeydew cubes held in air or controlled atmosphere (CA) of 2% 0₂+ 10% CO₂ at 5C and 4%0₂+ 10% CO₂ at 10C. The CA was beneficial in maintaining quality of honeydew cubes. Quality deteriorated rapidly with concomitant increase in respiration rate during the latter half of the 6-day at 10C or 10-day at 5C shelf-life. The shear force of samples was maintained by CA at 10C, but the visual quality was poor when that benefit was still noticeable. At 5C, an effect ofCA was not noted because the low temperature did not allow the shear force to decrease. The bacterial population was less on honeydew cubes held in CA than in air. Modified atmosphere with these gas mixtures would be beneficial in maintaining quality and retarding microbial growth on honeydew cubes, but strict temperature control is essential to avoid anaerobic respiration.     

CHANGES IN 'DELICIOUS' APPLE BROWNING AND SOFTENING DURING CONTROLLED ATMOSPHERE STORAGE

High CO₂ conditions offered no advantage over normal CA storage in terms of reduced ‘Delicious’ apple browning or softening during a 28 week storage period. After approximately 7–14 weeks in CA storage, ‘Delicious’ apples showed significant losses in PPO activity, browning tendency and firmness. Electrolyte leakage reached a maximum at 11.5 weeks and declined, while total phenolics remained fairly constant. The changes observed may indicate a loss in membrane integrity and decompartmentalization after 7–14 weeks of storage, which may in turn allow for increased enzymatic browning. Polygalacturonase activity was only detectable at harvest. Holding apples for additional time in air following removal from CA storage appears to accelerate changes in these characteristics.     

苹果贮藏中腐败变质的微生物学分析

本文从腐烂变质的苹果中,分离出引起苹果病变的微生物,并加以分类、研究,以探讨苹果贮藏过程中腐败变质的微生物学原因,为研究防腐保鲜技术提供一定的理论基础。