Estimasi Umur Simpan Pliek-U Berdasarkan Kadar Air Menggunakan Model Arrhenius dan Metode Q10

Abstrak. Penelitian ini bertujuan untuk menduga umur simpan Pliek-U menggunakan model Arrhenius dan metode Q10. Sebanyak 6 sampel Pliek-U yang sudah diketahui kadar air awalnya diberikan perlakuan suhu ekstrim 50, 60, dan 70˚C sampai kondisi Pliek-U mengalami penurunan mutu yang ditandai dengan perubahan warna dan bau. Perubahan berat sampel diamati dalam interval 30 menit. Selanjutya dilakukan perhitungan kadar air Pliek-U dan nilainya diplotkan dalam grafik di mana koordinat x nya sebagai waktu dan koordinat y nya sebagai kadar air. Gradien grafik adalah laju reaksi perubahan kadar air Pliek-U (k). Model Arrhenius adalah hasil plot nilai ln k terhadap 1/T dalam skala Kelvin. Selanjutnya dihitung nilai Q10 dan umur simpan Pliek-U dengan asumsi bahwa umur simpan sampel pada suhu ruang (30ºC) adalah 32 bulan. Hasil penelitian ini menunjukkan nilai k Pliek-U pada suhu 50ºC 0,0621 dan nilai R2 sebesar 15,52%. Nilai k Pliek-U pada suhu 60ºC adalah 0,0826 dan nilai R2 sebesar 67,9%, dan nilai k Pliek-U pada suhu 70ºC adalah 0,0877 dan nilai R2 sebesar 54,39%. Persamaan Arrhenius Pliek-U berdasarkan perubahan kadar air adalah k = 27,454 . e-1.925(1/T) dengan R2 sebesar 91,47%. Nilai faktor percepatan reaksi (Q10) Pliek-U adalah 1,214. Umur simpan Pliek-U dapat ditentukan dengan persamaan tT1=32 .1,214(∆T/10).Shelf-life estimation of Pliek-U based on moisture changes by using Arrhenius and Q10 approachAbstract. The study aimed to predict the shelf-life of Pliek-U by using Arrhenius and Q10 approach. About 6 samples of Pliek-U, already known its moisture, were exposed to high temperatures of 50, 60, dan 70ºC to reach degradation quality characterized by color and odor changes. The alteration of weight was also observed at interval of 30minutes. Based on these data, the changes of moisture were calculated and the trend was drawn on a XY scatter chart. The gradien of the chart was the reaction rate of quality degradation (k). Then, the Arrhenius model was constructed by plotting ln k and 1/T (K) into a graph. Lastly, the Q10 and shelf-life were calculated by using assumption that the shelf-life at room temperature was about 32 months. Results showed that the k-value and R-square of Pliek-U at 50˚C was 0.0621 and 15.52%, respectively. The k-value and R-square of Pliek-U at 60˚C was 0,0826 and 67,9%, whereas the k-value and R-square of Pliek-U at 70˚C was 0,0877 and 54,39%. The Arrhenius model of Pliek-U based on moisture changes was k = 27,454. e-1.925(1/T) and R-square was 91.47%. The Q10-value of Pliek-U was 1,214 and the shelf-life of Pliek-U can be adjusted by using the model tT1=32 .1,214(∆T/10).

Warming Changed Soil Respiration Dynamics of Alpine Meadow Ecosystem on the Tibetan Plateau

Alpine meadow system underlain by permafrost on the Tibetan Plateau contains vast soil organic carbon and is sensitive to global warming. However, the dynamics of annual soil respiration (Rs) under long-term warming and the determined factors are still not very clear. Using open-top chambers (OTC), we assessed the effects of two-year experimental warming on the soil CO2 emission and the Q10 value (temperature sensitivity coefficient) under different warming magnitudes. Our study showed that the soil CO2 efflux rate in the warmed plots were 1.22 and 2.32 times higher compared to that of controlled plots. However, the Q10 value decreased by 45.06% and 50.34% respectively as the warming magnitude increased. These results suggested that soil moisture decreasing under global warming would enhance soil CO2 emission and lower the temperature sensitivity of soil respiration rate of the alpine meadow ecosystem in the permafrost region on the Tibetan Plateau. Thus, it is necessary to take into account the combined effect of ground surface warming and soil moisture decrease on the Rs in order to comprehensively evaluate the carbon emissions of the alpine meadow ecosystem, especially in short and medium terms.

Pendugaan Umur Simpan Kembang Kol Berdasarkan Total Padatan Terlarut Dengan Model Arrhenius dan Q10

Abstrak. Informasi umur simpan kembang kol sangat penting untuk proses penanganan pasca panennya, sehingga dapat mengurangi resiko kerugian yang dihadapi oleh para petani dan pedagang. Penelitian ini bertujuan untuk mengetahui apakah model Arrhenius dan Q10 dapat digunakan untuk menduga umur simpan kembang kol berdasarkan total padatan terlarut. Kembang kol pilihan yang diperoleh dari pasar lokal disimpan dengan 5 variasi suhu ekstrim yaitu 50˚C, 55˚C, 60˚C, 65˚C, dan 70˚C. Selama penyimpanan tersebut dilakukan pengamatan nilai TPT sampai keadaan kembang kol sudah tidak layak untuk dikonsumsi lagi. Data perubahan nilai TPT diplotkan ke grafik dan modelnya dibaca dengan pendekatan linier. Nilai k yang menunjukkan laju reaksi perubahan TPT merupakan kemiringan dari model. Hasil plot ln k terhadap 1/T dalam skala Kelvin membentuk persamaan linier yang merupakan model Arrhenius. Penyimpanan kembang kol pada suhu ruang dilakukan untuk menentukan umur simpan aktual. Kemudian dengan nilai Q10 ditentukan umur simpan kembang kol pada berbagai suhu. Hasil penelitian menunjukkan bahwa terjadi fluktuasi nilai TPT selama penyimpanan kembang kol pada suhu ekstrim. Pada suhu 50˚C terjadi peningkatan TPT sebesar 0,001%brix per jam, pada suhu 55˚C terjadi peningkatan TPT sebesar 0,005%brix per jam, sedangkan pada suhu 65˚C dan 70˚C terjadi penurunan TPT sebesar 0,001%brix per jam. Nilai R2 yang diperoleh dari model linier ini sangat rendah yaitu 3-43%. Persamaan Arrhenius penurunan TPT kembang kol adalah dengan R2 sebesar 12,7%. Nilai faktor percepatan reaksi (Q10) TPT buah kembang kol adalah 0,73, sedangkan umur simpan aktual buah kembang kol pada suhu 29˚C adalah 5 hari. Hasil pendugaan umur simpan kembang kol pada suhu 5, 10, 15, 20, dan 25˚C adalah 2,3 hari, 2,7 hari, 3,2 hari, 3,8 hari, dan 4,4 hari. Hasil pendugaan ini belum sesuai dengan umur simpan actual kembang kol.Shelf-life Estimation of Cauliflower based on Total Soluble Solids by using the Arrhenius and Q10 ApproachAbstract. The shelf-life information of cauliflower is very important for the good post harvest handling thus it can reduce loss facing by farmers or sellers. The study aimed to estimate the shelf-life of cauliflower based on its total soluble solid (TSS) by using Arrhenius and Q10 approach. The selected cauliflowers obtained from the local market were stored at extreme temperatures i.e. 50, 55, 60, 65 and 70˚C. During storage at extreme temperature, the TSS values were determined until the cauliflowers quality broken. The TSS data were plot into a graph as linear model. The k values were the slope of the curve. The linear curve between ln k value and 1/T at unit of K performed the Arrhenius model. The storage at room temperature was also conducted to observe the real shelf-life of cauliflower. Finally, by using the Q10 value, the shelf-life of cauliflower was estimated. Results showed that there were fluctuated changes of TSS during storage. At temperature of 50˚C the incident increase of TSS was about 0.001%brix hourly, at temperature of 55˚C the increase of TSS was about 0.005%brix hourly, whereas at temperature of 65 and 70˚C, the decrease of TSS was about 0.001%brix hourly. The R-square values were very low from3 to 43% only. The Arrhenius model of the TSS changes in cauliflower was(R2 =12.7%). The Q10 value was 0.73, and the real shelf-life of cauliflower at 29˚C was 5 days. The shelf-life estimations of cauliflower at 5, 10, 15, 20, and 25˚C were 2.3 days, 2.7 days, 3.2 days, 3.8 days, and 4.4 days, respectively. These estimated results of shelf-life were not suitable with the actual shelf-life.Therefore, it is necessary to study the shelf-life esrtyimation of cauliflower by using other parameters such as vitamin A and vitamin C.

Pendugaan Umur Simpan Tomat (Lycopersium esculentum Mill) berdasarkan Kandungan Total Padatan Terlarut dengan Model Arrhenius dan Q10

Abstrak. Informasi umur simpan tomat sangat penting untuk proses penanganan pasca panennya sehingga dapat mengurangi resiko kerugian yang dihadapi oleh para petani dan pedagang. Penelitian ini bertujuan untuk mengetahui apakah model Arrhenius dan Q10 dapat digunakan untuk menduga umur simpan tomat berdasarkan nilai total padatan terlarut (TPT). Tomat segar terbaik yang diperoleh dari pasar induk disimpan dengan 3 variasi suhu ekstrim yaitu 50˚C, 60˚C dan 70 ˚C. Selama penyimpanan tersebut dilakukan pengamatan nilai TPT setiap 1 jam sekali, sampai keadaan tomat sudah tidak layak untuk dikonsumsikan lagi. Peralatan yang digunakan adalah refraktometer digital. Analisis model Arrhenius dilakukan dengan pendekatan persamaan linier. Pendugaan umur simpan dilakukan dengan metode Q10. Hasil penelitian menunjukkan bahwa model Arrhenius perubahan TPT tomat adalah k = 7,46x1012. e -8666/T . Energi aktivasi perubahan TPT buah tomat adalah 17.158 kal/mol. Nilai Q10 diperoleh sebesar 2,18. Pendugaan umur simpan dapat dilakukan dengan pendekatan ini baik menggunakan basis suhu penyimpanan 10 maupun 30 °C. Umur simpan tomat pada suhu 30 °C adalah 4,4 dan 5 hari, sedangkan umur simpan tomat pada suhu 10 °C adalah 21 dan 23,8 hari. Perlu penelitian lanjutan untuk menduga umur simpan tomat menggunakan parameter mutu lain seperti vitamin C dan kekerasan untuk meningkatkan validitas hasil pendugaan umur simpannya. The prediction of Tomato shelf life Based on Its Total Soluble Solid by Using Arrhenius and Q10 Model Abstract. The information about shelf life of tomato is necessary for its post harvest handling to reduce the loss facing by farmers and sellers. The study aimed to observe that the Arrhenius model and Q10 can be used to estimate the shelf life of tomatoes based on its total soluble solid (TSS). The fresh tomatoes obtained from the market were stored at three extreme temperatures i.e. 50˚C, 60 ˚C, and 70 ˚C. During the storing, the TSS was analyzed every hour, until the tomatoes quality was decreased. The TSS was observed by using refractometer. The Arrhenius model were evaluate through the TSS model in linier model. The shelf life estimation were calculated by Q10 method. Results showed that the Arrhenius model of TSS changes in tomatoes was k = k = 7.46x1012. e -8,666/T. The energy activation of TSS changes was about 17,158 kal/mol. The Q10 value was 2.18. The estimation of tomato shelf life can be run successfully by using the Arrhenius and Q10 approach, both at storage temperature basis of 10 and 30 °C. The shelf life of tomatoes at storage temperature 30 were 4.4 and 5 days, respectively, whereas at storage temperature 10 °C were 21 and 23.8 days, respectively. Therefore it is recommended for the further study to evaluate the other quality parameter changes such as vitamin C and hardness to improve the model.

Seasonal variations in soil respiration and temperature sensitivity under three land-use types in hilly areas of the Sichuan Basin

CO2 emissions from soils were measured under 3 land-use types at the adjacent plots of forest plantation, grassland, and cropland from January 2005 to December 2006. Mean soil CO2 efflux rates measured during the 2-year study varied from 59 to 527 mg CO2/m2.h in forest plantation, 37 to 498 mg CO2/m2.h in grassland, and 32 to 397 mg CO2/m2.h in cropland. Soil respiration in the 3 types of land-use showed a similar seasonal pattern in variation during both years, in which the single-peaked curve occurred in early summer and the minimum in winter. In particular, the date of maximum soil CO2 efflux rate in cropland occurred about 30 days earlier than in forest and grassland in both 2005 and 2006. The relationship of soil respiration rate (R) with soil temperature (T ) and soil moisture (W ) fitted well to the equation R = β0eβ1TW β2 (a, b, c were constants) than other univariate models which consider soil water content or soil temperature alone. Soil temperature and soil moisture together explained 69–92% of the temporal variation in soil respiration in the 3 land-use types. Temperature sensitivity of soil respiration (Q10) was affected positively by soil moisture of top 0.1 m layer and negatively by soil temperature at 0.05 m depth. The relationship between Q10 values and soil temperature (T ) or soil moisture (W ) indicated that a 1°C increase in soil temperature at 0.05 m depth will reduce the Q10 value by 0.07, 0.05, and 0.06 in forest, grassland, and cropland, respectively. Similarly, a 1% decrease in soil moisture of the top 0.1 m layer will reduce the Q10 value by 0.10, 0.09, and 0.11 in forest, grassland, and cropland.

Temperature-related changes in respiration and Q10 coefficient of Guava

Guava (Psidium guajava L.) is a tropical fruit that presents fast post-harvest ripening; therefore it is a very perishable product. Inappropriate storage temperature and retail practices can accelerate fruit quality loss. The objective of this study was to evaluate the respiratory activity (RA), the ethylene production (EP) and Q10 of guava fruit at different storage temperatures. 'Paluma' guava fruits were harvested at maturity stage 1 (dark-green skin) and stored at either 1, 11, 21, 31 or 41ºC; RA and EP were determined after 12, 36, 84 and 156 h of storage. RA and EP rates at 1 and 11ºC were the lowest - 0.16 and 0.43 mmol CO2 kg-1 h-1 and 0.003 and 0.019 µmol C2H4 kg-1 h-1, respectively. When guavas were stored at 21ºC, a gradual increase occurred in RA and EP, reaching 2.24 mmol CO2 kg-1 h-1 and 0.20 µmol C2H4 kg-1 h-1, after 156 h of storage. The highest RA and EP were recorded for guavas stored at 31ºC. In spite of high RA, guavas stored at 41ºC presented EP similar to guavas stored at 11ºC, an indicator of heat-stress injury. Considering the 1-11ºC range, the mean Q10 value was around 3.0; the Q10 value almost duplicated at 11-21ºC range (5.9). At 21-31ºC and 31-41ºC, Q10 was 1.5 and 0.8, respectively. Knowing Q10, respiratory variation and ripening behavior in response to different temperatures, fruit storage and retail conditions can be optimized to reduce quality losses.

The Influence of Hyperoxia, Hypoxia and Temperature on the Respiratory Physiology of the Intertidal Rockpool Fish Gobius Cobitis Pallas

The influence of hypoxia, hyperoxia and temperature on the oxygen consumption, heart rate and ventilation frequency of the intertidal rockpool fish Gobius cobitis Pallas were investigated to examine the respiratory adaptations of this species to intertidal conditions. The standard mass-specific oxygen consumption (MOO2 × m−1) during normoxia, calculated for a 50-g fish, averaged 1.27 mmol O2kg−1h−1 at 12.5°C and 3.62mmol O2kg−1h−1 at 25°C. The Q10 value for oxygen consumption averaged 2.3. During a stepwise reduction of oxygen partial pressure (POO2) the oxygen consumption was maintained down to a critical oxygen tension, Pc, of approximately 43 Torr (1 Torr = 133.3 Pa). Ventilatory frequency increased progressively while heart rate remained constant until the POO2 was reduced below 16 Torr. During hyperoxic exposure (POO2 = 150–450 Torr), oxygen consumption remained constant at 12.5 and at 25°C (Q10 = 2.3). Hyperoxia had no effect on heart rate, although ventilation frequency decreased with increasing POO2 (to the same extent at both temperatures), indicating the overriding effect of hyperoxia on ventilatory frequency. Gobius cobitis appears to be well-adapted to the respiratory stresses which occur on a daily basis within intertidal rockpools.

Metabolic activity of zooplankton from the Antarctic Ocean

Eight species of live zooplankton were transported from the Antarctic Ocean to a tropical laboratory in Queensland, Australia. Their respiration and ammonia excretion rates measured at - 0.5� C were in the order of 0.15-0.55 �l O2/mg dry wt. h and 0.002-0.06�g N mg dry wt. h, respectively. As an indirect estimate enzyme activity of the respiratory electron transport system (ETS) was determined on frozen specimens of 15 zooplankton species brought back from the Antarctic Ocean. The ratio of ETS activity to respiration rate measured in this study was 1.863 � 0.738 (n = 12). The respiration rates thus directly and indirectly obtained were in agreement with results of previous workers. Effect of temperature on respiration and ammonia excretion rates were examined on two selected animal groups of zooplankton- copepods belonging to the family Calanidae and euphausiids of the genus Euphausia- and the results were compared with those for species from other seas where the temperature varies from 5.0 to 27.6�C. From this comparison, acceleration of the rate (standardized to 1 mg dry wt of body) by the increase of temperature (expressed as a Q10 value) was 2.18 for respiration rate and 2.58 for ammonia excretion rate.