ACOUSTIC PROPERTIES OF PAPAYA

The speed of sound in papaya pulp was found to be (1.6 ± 0.3) × 10⁴cm/s. The absorption of sound varied, approximately, as the square root of the acoustic frequency. Measurements were made to test the tolerance of papaya to high acoustic intensity. Discoloration and softening occur at 43 W/cm² for exposures of 30s.     

番木瓜混浊果汁的工艺研究

以番木瓜原浆为主要原料，白砂糖等为辅料，研究了番木瓜混浊果汁生产工艺及其关键工序。结果表明：采用正交实验并进行感官评定，确定最佳糖酸比；0．03％CMC-Na与0．025％黄原胶复配可获得理想的稳定效果。其最佳配方为：番木瓜原浆15％、白砂糖10％、柠檬酸0．10％、黄原胶0．025％、CMC-Na0、03％。该产品具有番木瓜清香，是一种天然、营养丰富的新型保健饮料。     

EFFECT OF POSTHARVEST HOT AIR AND FUNGICIDE TREATMENTS ON THE QUALITY OF 'MARADOL' PAPAYA (CARICA PAPAYA L.)

Papaya (Carica papaya L.) fruit is very perishable with a maximum postharvest life of 4 weeks. The effect of forced moist (100% RH) or dry (50%) hot air with or without Thiabendazole (TBZ at 1.2 g active ingredient/L) on the chilling injury (CI), fungi development and quality of ‘Maradol’papaya fruit stored at 5C or 20C for up to 42 days was investigated. Moist hot air at 48.5C or 50C for 4 h caused fruit injury. Dry air at 48.5C for 4 h, alone or in combination with TBZ, decreased CI intensity and fungi development, and the best effect was achieved by combining dry heat treatment and TBZ, without causing negative effects on fruit quality and without causing heat injury. Hot air treatment, especially in combination with TBZ, decreased growth of inoculated Colletotrichum gloeosporioides. Trehalose was not detected in papaya, probably due to the presence of trehalase. Hot water treatment, with or without TBZ, did not cause any negative effect on the content of β-carotene and lycopene.     

IMPACT OF MODIFIED ATMOSPHERE PACKAGING ON THE OSMODEHYDRATED PAPAYA STABILITY

Papaya pieces were osmotically dehydrated in a 50°Brix sucrose solution containing calcium lactate (0.05 M) and lactic acid (0.02 M) as additives for 1 h at 25C, packed in polyethylene terephthalate (PET) containers and stored at 5C for 15 days. Fresh fruit pieces packed in PET containers and under atmosphere condition were used as control samples. Sensory acceptance, microbiological count, CO₂ and O₂ content inside the packages, color, mechanical properties and weight loss of the product were evaluated. PET containers prevented weight loss during storage. The utilization of calcium lactate as additive was effective in maintaining fruit hardness during refrigerated storage. The use of passive modified atmosphere associated with refrigeration was adequate to preserve the osmotically dehydrated fruit for 15 days, showing a good sensory acceptance by the consumers during the storage time.     

THERMAL INACTIVATION of PECTINESTERASE IN PAPAYA PULP (pH 3.8)

In order to establish the thermal process required by acified papaya pulp (pH 3.8) var "formosa", a study was carried out on the kinetics of thermal inactivation of the heat resistant enzymes present in the pulp. Since no peroxidase activity was detected, the study was focused on pectinesterase.
The heat inactivation curves at 75, 77 and 80C showed a change in slope indicating the presence of two different portions of the enzyme, one heat labile and the other heat resistant. the decimal reduction times (D value) of pectinesterase were 0.8, 0.3 and 0.2 min for the heat labile portion and for the heat resistant portion 16.7, 7.2 and 3.7 min, respectively.
The temperature-dependency factor for the heat labile portion was 9.2C and 7.8C for the thermostable portion, while the activation energies were 258.3 and 304.4 Kj/mol. These values were within the range of 167.5–418.7 Kj/mol reported in the literature for the thermal inactivation of enzymes. Thermal destruction studies with Clostridium pasteurianum, conducted at the same temperatures used for the inactivation of the enzyme, showed that the heat resistant portion of pectinesterase presented greater thermal resistance and should be used as target for the establishment of the required process.     

EFFECT OF PAPAYA PULP ADDITION ON THE GROWTH OF LACTOBACILLUS ACIDOPHILUS

Effect of papaya pulp addition to skim milk on the growth characteristics of five strains of Lactobacillus acidophilus was investigated. All the strains tested exhibited higher viable counts, shorter generation time, increased acid production, greater sugar utilization and fall in pH upon addition of papaya pulp. The generation time, acid production, sugar utilization and pH values at the end of 18 h fermentation of skim milk by different strains were 150–200 min, 0.29–1.73%, 0.39–2.22 g/100 mL and 3.85–6.10, respectively. The corresponding values for 10% papaya pulp added skim milk blend were 120–143 min, 0.51–1.84%, 0.70–2.79 g/100 mL and 3.70–5.10, respectively. Organoleptic evaluation revealed that papaya pulp addition imparted firmness to the coagulum and thus enhanced the acceptability of the product by eliminating the problem of wheying-off and improved flavor.     

转基因番木瓜及其深加工制品的PCR检测方法

对番木瓜不同材料及其深加工制品的核酸提取方法进行了优化。成功提取出DNA。选取番木瓜特异性的内源蛋白PAPAIN基因片段作为内参基因，用于检验提取DNA的质量，有效避免了聚合酶链式反应PCR的假阴性并能用于确定检测样品中是否含有番木瓜成分。选取国内目前应用比较多的外源目的基因环斑病毒外壳蛋白（CP）基因以及复制酶（RP）基因作为品系鉴定的基因。适用于出入境检验检疫部门和农业部门对转基因番木瓜及其制品的检验监测。     

胡萝卜木瓜南瓜复合保健饮料的研制

以胡萝卜、木瓜、南瓜为主要原料,采用正交试验设计方法、单因素试验设计及感官评定研究胡萝卜、木瓜、南瓜复合果蔬饮料的最佳配方.试验结果表明,最佳配方为:胡萝卜木瓜南瓜体积比为10:30:20,白糖12%,柠檬酸0.26%,琼脂0.1%.     

THERMAL DESIGN PROCESS FOR ACIDIFIED CANNED PAPAYA (Carica papaya L.) PULP

Previous results showed that the heat resistant portion of pectinesterase in the acidified papaya pulp var. “formosa” presented greater thermal resistance than Cl. pasteurianum. Based on this, and determined F^7.8C_77C, a value of 12.3 min was calculated using the heat resistant portion of pectinesterase as the target for the process, and applying 1.7 decimal reduction of the activity of the heat resistant enzyme (98% inactivation). Using Shiga (1976) an empirical relationship and a heating time of 12.9 min in water bath at 97C was established for the process. Three processing tests were carried out under these conditions using 6 cans per test. The processing values varied from 12.33 to 12.75 min at 77C. Statistical analysis showed no significant difference between tests and among cans as well as test at the 0.05 and 0.01 α level. After processing the cans, gelatinization, activity of remaining enzyme and micro-organism growth were not detected. This shows that the process was able to inactivate the heat resistant portion of pectinesterase and kill the natural micro-flora present on the pulp. By considering the initial variation of the pectinesterase activity in the pulp and F^7.8C_77C - value of 16.7 min, a safety factor for the process was applied. This process was equivalent to 15 min of heating in water bath at 97C and corresponded to 2.3 decimal reductions in activity of heat resistant pectinesterase. An inoculation pack study was performed to verify the microbiological safety of such process. Each can of papaya pulp was inoculated with 1 mL of a 10⁴ spore/mL suspension of Cl. pasteurianum. Swelling of the cans, growth after subculturing and pectinesterase were not detected after incubation, showing that the pulp could be safely processed. The storage test showed no significant changes in the color, flavor, aroma and texture of the canned acidified papaya pulp.