Kevin Yaptenco

The sea cucumber commonly known as sandfish (Holothuria scabra) is a high-value species that is often sourced from artisanal fishers in the Philippines. The traditional drying process involves a combination of smoking and sun-drying until a moisture content of 8%-10% is reached. However, dried sea cucumber, including sandfish, is often poorly dried; resulting in spoilage and mold growth during storage. To establish conditions for proper storage of dried sandfish, this study aims to develop moisture sorption isotherms (MSI) at 30°C, 45°C and 60°C at ten levels of water activity (aw) using an isopiestic method based on saturated salt solutions. Equilibrium moisture content (EMC) data were fitted with six mathematical models by non-linear regression analysis. Water vapor transmission rate (WVTR) of low-density polyethylene (PE) and oriented polypropylene (OPP) packaging film was also measured at 30°C and 35°C and a mass-balance model was used to predict shelf life and EMC during storag...

Respiration rate of whole tomato was modeled at 10, 15, and 17℃ using a closed respiration chamber system and different enzyme kinetics equations (with and without CO₂ inhibition). Oxygen and CO₂ levels predicted by the different models agreed well with experimental data from the closed system. The model with uncompetitive CO₂ inhibition was selected for further validation based on high R² values (≥ 0.993) and ease of use. Whole tomato was packed in 0.05 ㎜ low-density polyethylene (LDPE) or micro-perforated polypropylene (MPP) bags and stored at 10, 15, and 17℃. Measured O₂ transmission rate (TrO₂) for LDPE film followed Arrhenius kinetics with respect to temperature, ranging from 88 mLㆍm?²ㆍh?¹ㆍatm?¹ at 10℃ to 144 mLㆍm?²ㆍh-1ㆍatm?¹ at 17℃. Tr?₂ of the MPP film was fairly constant regardless of temperature, with a range of 420.6-485.3 mLㆍm?²ㆍh?¹ㆍatm?¹. Modified atmospheres developed in the simulated packages compared well with predictions based on the uncompetitive inhibition model an...

Near-infrared (NIR) spectroscopy was assessed in predicting maturity and eating quality of ‘Carabao’ mango fruit. A total of 1,200 fruits were harvested at the green stage at four different harvest dates [100, 110, 120 and 125 days after flower induction (DAFI)]. Fruits were scanned at the green and table-ripe stage (TRS) using NIR reflectance spectroscopy. The fruits were then measured destructively for the determination of dry matter (DM) content at the green stage, total soluble solids (TSS) and sensory attributes at the TRS. The best calibration models were achieved using partial least square regression (PLSR) analysis for predicting DM, TSS and maturity in the short wavelength region of 700 - 990 nm at 2-nm increment. Principal component analysis-linear discriminant analysis (PCA-LDA) was also used in classifying fruits according to maturity (in terms of DAFI) and eating quality (in terms of overall acceptability or OA). Based on R 2 values, PLSR models are suitable for quality...

Dried sandfish ( Holothuria scabra ) is often poorly dried by artisanal fishers in the Philippines, resulting in downgrading of the product. To establish recommended moisture content (MC) for a stable product, this study aimed to develop moisture sorption isotherms (MSI) at 30, 45 and 60°C at ten levels of water activity ( a w ) using an isopiestic method based on saturated salt solutions. MSI data was fitted to six mathematical models by non-linear regression analysis. Water vapor transmission rate (WVTR) of low-density polyethylene (PE) and polypropylene (OPP) film was measured at 30 and 35 o C. A mass-balance model was used to predict shelf life and moisture content during storage based on MSI and WVTR data. MSI of H. scabra followed a Type III curve, which was best fitted to a Peleg model. For a stable product, the recommended range for MC during storage was 0.12-0.18 g g -1 dry matter to avoid over- or under-drying; this corresponded to a w of 04-0.6. Predicted shelf life for P...

ABSTRACT Tissue samples from cold-stored (0°C) 'Danshaku' potato tuber which underwent low temperature sweetening (LTS) were analyzed by differential scanning calorimetry (DSC) using a heating rate of 5°C /min. Results showed that LTS significantly lowered the onset temperature of melting. Tubers stored at 10°C did not sweeten and showed insignificant reduction of onset temperature. Total sugar levels were significantly related to Tp, To and Te while off was significantly related to moisture content of the sample. The primary endotherm (average To=-3. 86°C) representing extracellular melting of water was observed for tubers stored at 10°C and 0°C ; a secondary endotherm representing freezing of intracellular water was observed in 41.18% of tissue samples from tubers stored at 10°C (average To=-3.22°C). Only 11.11% of tissue samples from tubers stored at 0°C showed a secondary endotherm (average To=-12.20°C), implying that high sugar levels reduced lethal intracellular freezing in cellular compartments. Hence, sugar accumulation induced by cold conditions may be a mechanism to delay freezing and reduce its harmful effects on cell compartmentation and function.

Publikationsansicht. 5206928. Performance evaluation of a laboratory scale steep battery for corn wet milling / (1993). Yaptenco, Kevin Fernandez. Abstract. Printout.. Thesis (MS)--University of Illinois at Urbana-Champaign, 1993.. Vita.. ...