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Kevin Yaptenco

University of the Philippines Los Baños, Institute of Agricultural Enginering, Faculty Member

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Professor at the Institute of Agricultural Engineering of the University of the Philippines Los Banos. Research interests include postharvest handling and storage of perishable crops (since 1989), drying and packaging of food and agricultural materials (since 2008).
Phone: 0495363291
Address: Institute of Agricultural Engineering
Pili Drive
University of the Philippines Los Banos
Laguna 4031

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Papers by Kevin Yaptenco

Gas transmission rates across Carabao mango peel at different stages of maturity and ripeness

Gas transmission rate through fruit peel is needed to understand gas exchange between fruit and t... more Gas transmission rate through fruit peel is needed to understand gas exchange between fruit and the environment. It can be used to design packaging material and formulate edible coatings to be used by the fruit. It can also be used to predict oxygen consumption and possible carbon dioxide injury which could affect ripening and could predict the internal gas level inside the fruit. Oxygen and carbon dioxide transmission rates (O2TR and CO2TR) of mango (Mangifera indica, L.) peel at different stages of maturity and ripeness which were stored under two temperature regimes were measured using gas diffusion chamber. Nitrogen gas was flushed inside the chamber to decrease the oxygen level. Then a gas mixture of known concentration was flushed in the chamber and the concentration inside the chamber was measured through time. The Exponential Decay Method of Gas Transmission Rate of Films as described by Moyls (1992) was used to relate partial pressure of the gas concentration inside the chamber and the outside condition. Results showed that overmature fruit peel-PCI3 under 27°C had the highest O2TR and CO2TR (1.636 mLO2 /cm 2-hr-4.744 mLCO2 /cm 2-hr) while immature fruit peel-PCI1 under 14°C had the lowest O2TR and CO2TR (1.104 mL O2 /cm 2-hr-3.321 mL CO2 /cm 2-hr). At constant temperature, gas transmission rates increase with maturity and as the fruit peel turns yellow.

A Laboratory Countercurrent Steep Battery for Corn Wet Milling

Gas Transmission Rates of Polyethylene and Polypropylene Films Gas Transmission Rates of Commercially Available Polyethylene and Polypropylene Films for Modified Atmosphere Packaging

Oxygen transmission rates (OTR) of low-density polyethylene (PE) and polypropylene (PP) films wer... more Oxygen transmission rates (OTR) of low-density polyethylene (PE) and polypropylene (PP) films were measured at 10, 15 and 17 deg C using the whole-bag method of Moyls (2004) for unperforated films. PE films with a nominal thickness of 30, 40, 60 and 80 µm (PE30, PE40, PE60 and PE80, respectively) were analyzed; thickness of the PP film was 40 µm. Oxygen and CO2 transmission rates (CO2TR) of 35-µm micro-perforated polypropylene (MPP) were measured at 10, 15, and 17 deg C using the method described by Ozdemir et al. (Ozdemir I, Monnet F, Gouble B. 2005. Postharvest Biol Tech 36:209-213). Temperature effects on unperforated PE and PP films followed Arrhenius kinetics (R2 > 0.970). Activation energy (Ea) of PE film had a range of 28.1–35.0 kJ mol-1 ; for PP film, Ea was 38.1 kJ mol-1. In general, Ea of PE film increased as film thickness (tF) increased. Q10-Tr values at 10–20 deg C for PE and PP were 1.50–1.66 and 1.74, respectively. Temperature had no definite effect on OTR and CO2TR of MPP. Mean OTR and CO2TR for MPP were 10,848 and 9,554 mL m-2 d-1 , respectively. The average perforation diameter (Dmp) and density (dmp) was 41.0 µm and 125 perforations per m2 , respectively, for a 20 cm x 28 cm bag. Comparisons with published data showed the sample film to have gas transmission rates at the lower end of the range for such types of packaging film.

Nondestructive Firmness Measurement as a Maturity Index for 'Carabao' Mango (Mangifera indica L.) Fruit

'Carabao' mango was harvested green at different stages of maturity [100, 105, 110, 115, 120 and ... more 'Carabao' mango was harvested green at different stages of maturity [100, 105, 110, 115, 120 and 125 d after flower induction (DAFI)] and subjected to nondestructive firmness test using a universal testing machine. A 7.9-mm diameter plunger with rounded tip (6.9-mm radius of curvature) was pressed onto whole fruit at 10 mm min-1 crosshead speed, to produce deformations of 0.8, 1.3, and 1.8 mm; additional fruits were tested until rupture for comparison. Total soluble solids (TSS), titratable acidity (TA) and pH were measured at the green stage and at the table-ripe stage (TRS) after ripening at 25 °C. Sensory analysis was performed at TRS to determine the best harvest maturity. Results showed no significant differences in TSS, TA and pH between maturities at the green stage; hence, physico-chemical properties could not be used to test for maturity. Sensory analysis at TRS showed that fruit harvested at 115–120 DAFI gave the best eating quality in terms of aroma, sweetness, sourness, flavor and overall acceptability. Fruits harvested at 125 DAFI showed significantly lower sensory scores. Significant differences in rupture force (F R , kN) and fruit stiffness (B, kN mm-1 of deformation) were observed between maturities at the green stage; however, the nondestructive deformation test at 0.8 mm was more sensitive to fruit maturity. Fruits harvested at 115–120 DAFI had significantly lower values for B and load ratio at 0.8-mm to 0.5-mm deformation (F 0.8 /F 0.5) compared with earlier harvest dates. Analysis of the normal distribution curve of a prediction set of 40 mature (MAT) fruits showed that 80% of the samples had B ≤ 1.360 kN mm-1 and F 0.8 /F 0.5 ≤ 1.883. Based on the use of signal detection theory and these values as thresholds, 66.3% (by B) and 58.8% (by F 0.8 /F 0.5) of immature or overmature (I/O) fruit could be detected. Analysis of a separate validation set of fruit using the same threshold values gave respective detection rates of I/O fruit of 68.8% using B and 60.0% using F 0.8 /F 0.5 .

Respiration Modeling of Cherry Tomato (cv. Coco) at Different Tempera- tures for Modified Atmosphere Packaging Applications

Oxygen depletion and CO2 accumulation in a closed respiration system containing fresh cherry toma... more Oxygen depletion and CO2 accumulation in a closed respiration system containing fresh cherry tomato (cv. Coco) at the light-red stage of ripeness was monitored. Experiments were carried out at 10, 12.5, 17 and 20 deg C. Five models based on enzyme kinetics equations were evaluated using the data generated ; the uncompetitive inhibition model was selected for further validation based on goodness of fit to experimental data. Effect of temperature on model parameter Vm followed Arrhenius kinetics for both O2 consumption and CO2 production rates (R2 of 0.999 and 0.974, respectively). Computer simulations showed that 0.30–0.45 kg of cherry tomato (cv. Coco) could be packed in 20 cm x 20 cm 30-µm polyethylene (PE) bags and held at 10–20 deg C without producing anaerobic O2 levels; for 40-µm PE, predicted headspace O2 concentration was below the recommended minimum of 3% at this temperature range. The model predicted gas levels accurately in respiration chambers containing a batch of fruits harvested from a different farm and on a different harvest date; comparison of predicted and measured gas levels showed r2 of 0.992 for both O2 and CO2. The model was less accurate in predicting O2 levels in actual 30-µm PE packs; r2 of predicted and measured gas levels were 0.975 and 0.939 for O2 and CO2 , respectively. Packaging trials proved that 30-µm PE could maintain an acceptable quality of fruits for 5 d at 20 deg C if fruits were defect-free. Optimum fill weight for a 20 cm x 20 cm pack was 0.45 kg.

Respiration modeling of whole tomato at different temperatures for modified atmosphere packaging

Respiration rate of whole tomato was modeled at 10, 15 and 17 deg C using a closed respiration ch... more Respiration rate of whole tomato was modeled at 10, 15 and 17 deg C 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 mm low-density polyethylene (LDPE) or micro-perforated polypropylene (MPP) bags and stored at 10, 15 and 17 deg C. Measured O2 transmission rate (TrO2) for LDPE film followed Arrhenius kinetics with respect to temperature, ranging from 88 ml•m-2•h-1•atm-1 at 10 deg C to 144 ml•m-2•h-1•atm-1 at 17 deg C. TrO2 of MPP film was fairly constant regardless of temperature, with a range of 420.6 – 485.3 ml•m-2•h-1•atm-1. Modified atmospheres developed in the simulated packages compared well with predictions based on the uncompetitive inhibition model and measured film transmission rates. Predicted steady state O2 and CO2 levels in LDPE packages reached 3% and 4-6%; for MPP, predicted steady state conditions were 9-12% O2 and 8-13% CO2.

Good practice in the design, management and operation of a fresh produce packing-house

by Kevin Yaptenco and Rosa Rolle

Market oriented production trends across Asia and the Pacific region, spurred by growth in the fo... more Market oriented production trends across Asia and the Pacific region, spurred by growth in the food service, supermarket and export sectors, rising living standards and growing consumer awareness necessitate a shift toward improved handling practices in fresh produce supply chains. Within the post-harvest system, the packing-house serves as a control point where quality management can be applied to assure a reliable supply of produce of good quality. Packinghouses also serve as sites for the effective implementation of strategies designed to eliminate or minimize microbial, chemical and physical contamination.

Sugar Accumulation as a Mechanism for Freezing Tolerance in Cold-Stored 'Danshaku' Potato Tuber (Solanum tuberosum L.)

food preservation science, 2000

ABSTRACT Tissue samples from cold-stored (0°C) &#39;Danshaku&#39; potato tuber which unde... more ABSTRACT Tissue samples from cold-stored (0°C) &#39;Danshaku&#39; 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.

Property Changes in Potato Tubers (Solanum tuberosum L.) During Cold Storage at 0 and 10°C

food preservation science, 2000

Starch Gelatinization Kinetics in Cold-Stored 'Danshaku' Potato Tubers (Solanum tuberosum L.)

food preservation science, 2000

Optimized drying parameters of water hyacinths

The study investigated the optimum drying conditions of water hyacinth to contribute in the impro... more The study investigated the optimum drying conditions of water hyacinth to contribute in the improvement of present drying processes. The effects of independent parameters (drying temperature, airflow rate, and number of passes) on the responses were determined using the Response Surface Methodology. The response parameters were composed of (1) final moisture content, (2) moisture ratio, (3) drying rate, (4) tensile strength, and (5) browning index. Box and Behnken experimental design represented the design of experiments that resulted in 15 drying runs. Statistical analysis evaluated the treatment effects. Drying temperature significantly affected the drying rate, moisture ratio, and browning index. Airflow rate had a significant effect only on the drying rate, while the number of passes significantly affected both the drying rate and browning index. The optimized conditions for drying the water hyacinth were at drying temperature of 90ˆC, airflow rate of 0.044m 3 /s, and number of passes equivalent to five. The best model that characterizes the drying of water hyacinth is a rational function expressed as:

Gas transmission rates across Carabao mango peel at different stages of maturity and ripeness

Gas transmission rate through fruit peel is needed to understand gas exchange between fruit and t... more Gas transmission rate through fruit peel is needed to understand gas exchange between fruit and the environment. It can be used to design packaging material and formulate edible coatings to be used by the fruit. It can also be used to predict oxygen consumption and possible carbon dioxide injury which could affect ripening and could predict the internal gas level inside the fruit. Oxygen and carbon dioxide transmission rates (O2TR and CO2TR) of mango (Mangifera indica, L.) peel at different stages of maturity and ripeness which were stored under two temperature regimes were measured using gas diffusion chamber. Nitrogen gas was flushed inside the chamber to decrease the oxygen level. Then a gas mixture of known concentration was flushed in the chamber and the concentration inside the chamber was measured through time. The Exponential Decay Method of Gas Transmission Rate of Films as described by Moyls (1992) was used to relate partial pressure of the gas concentration inside the chamber and the outside condition. Results showed that overmature fruit peel-PCI3 under 27°C had the highest O2TR and CO2TR (1.636 mLO2 /cm 2-hr-4.744 mLCO2 /cm 2-hr) while immature fruit peel-PCI1 under 14°C had the lowest O2TR and CO2TR (1.104 mL O2 /cm 2-hr-3.321 mL CO2 /cm 2-hr). At constant temperature, gas transmission rates increase with maturity and as the fruit peel turns yellow.

A Laboratory Countercurrent Steep Battery for Corn Wet Milling

Gas Transmission Rates of Polyethylene and Polypropylene Films Gas Transmission Rates of Commercially Available Polyethylene and Polypropylene Films for Modified Atmosphere Packaging

Oxygen transmission rates (OTR) of low-density polyethylene (PE) and polypropylene (PP) films wer... more Oxygen transmission rates (OTR) of low-density polyethylene (PE) and polypropylene (PP) films were measured at 10, 15 and 17 deg C using the whole-bag method of Moyls (2004) for unperforated films. PE films with a nominal thickness of 30, 40, 60 and 80 µm (PE30, PE40, PE60 and PE80, respectively) were analyzed; thickness of the PP film was 40 µm. Oxygen and CO2 transmission rates (CO2TR) of 35-µm micro-perforated polypropylene (MPP) were measured at 10, 15, and 17 deg C using the method described by Ozdemir et al. (Ozdemir I, Monnet F, Gouble B. 2005. Postharvest Biol Tech 36:209-213). Temperature effects on unperforated PE and PP films followed Arrhenius kinetics (R2 > 0.970). Activation energy (Ea) of PE film had a range of 28.1–35.0 kJ mol-1 ; for PP film, Ea was 38.1 kJ mol-1. In general, Ea of PE film increased as film thickness (tF) increased. Q10-Tr values at 10–20 deg C for PE and PP were 1.50–1.66 and 1.74, respectively. Temperature had no definite effect on OTR and CO2TR of MPP. Mean OTR and CO2TR for MPP were 10,848 and 9,554 mL m-2 d-1 , respectively. The average perforation diameter (Dmp) and density (dmp) was 41.0 µm and 125 perforations per m2 , respectively, for a 20 cm x 28 cm bag. Comparisons with published data showed the sample film to have gas transmission rates at the lower end of the range for such types of packaging film.

Nondestructive Firmness Measurement as a Maturity Index for 'Carabao' Mango (Mangifera indica L.) Fruit

'Carabao' mango was harvested green at different stages of maturity [100, 105, 110, 115, 120 and ... more 'Carabao' mango was harvested green at different stages of maturity [100, 105, 110, 115, 120 and 125 d after flower induction (DAFI)] and subjected to nondestructive firmness test using a universal testing machine. A 7.9-mm diameter plunger with rounded tip (6.9-mm radius of curvature) was pressed onto whole fruit at 10 mm min-1 crosshead speed, to produce deformations of 0.8, 1.3, and 1.8 mm; additional fruits were tested until rupture for comparison. Total soluble solids (TSS), titratable acidity (TA) and pH were measured at the green stage and at the table-ripe stage (TRS) after ripening at 25 °C. Sensory analysis was performed at TRS to determine the best harvest maturity. Results showed no significant differences in TSS, TA and pH between maturities at the green stage; hence, physico-chemical properties could not be used to test for maturity. Sensory analysis at TRS showed that fruit harvested at 115–120 DAFI gave the best eating quality in terms of aroma, sweetness, sourness, flavor and overall acceptability. Fruits harvested at 125 DAFI showed significantly lower sensory scores. Significant differences in rupture force (F R , kN) and fruit stiffness (B, kN mm-1 of deformation) were observed between maturities at the green stage; however, the nondestructive deformation test at 0.8 mm was more sensitive to fruit maturity. Fruits harvested at 115–120 DAFI had significantly lower values for B and load ratio at 0.8-mm to 0.5-mm deformation (F 0.8 /F 0.5) compared with earlier harvest dates. Analysis of the normal distribution curve of a prediction set of 40 mature (MAT) fruits showed that 80% of the samples had B ≤ 1.360 kN mm-1 and F 0.8 /F 0.5 ≤ 1.883. Based on the use of signal detection theory and these values as thresholds, 66.3% (by B) and 58.8% (by F 0.8 /F 0.5) of immature or overmature (I/O) fruit could be detected. Analysis of a separate validation set of fruit using the same threshold values gave respective detection rates of I/O fruit of 68.8% using B and 60.0% using F 0.8 /F 0.5 .

Respiration Modeling of Cherry Tomato (cv. Coco) at Different Tempera- tures for Modified Atmosphere Packaging Applications

Oxygen depletion and CO2 accumulation in a closed respiration system containing fresh cherry toma... more Oxygen depletion and CO2 accumulation in a closed respiration system containing fresh cherry tomato (cv. Coco) at the light-red stage of ripeness was monitored. Experiments were carried out at 10, 12.5, 17 and 20 deg C. Five models based on enzyme kinetics equations were evaluated using the data generated ; the uncompetitive inhibition model was selected for further validation based on goodness of fit to experimental data. Effect of temperature on model parameter Vm followed Arrhenius kinetics for both O2 consumption and CO2 production rates (R2 of 0.999 and 0.974, respectively). Computer simulations showed that 0.30–0.45 kg of cherry tomato (cv. Coco) could be packed in 20 cm x 20 cm 30-µm polyethylene (PE) bags and held at 10–20 deg C without producing anaerobic O2 levels; for 40-µm PE, predicted headspace O2 concentration was below the recommended minimum of 3% at this temperature range. The model predicted gas levels accurately in respiration chambers containing a batch of fruits harvested from a different farm and on a different harvest date; comparison of predicted and measured gas levels showed r2 of 0.992 for both O2 and CO2. The model was less accurate in predicting O2 levels in actual 30-µm PE packs; r2 of predicted and measured gas levels were 0.975 and 0.939 for O2 and CO2 , respectively. Packaging trials proved that 30-µm PE could maintain an acceptable quality of fruits for 5 d at 20 deg C if fruits were defect-free. Optimum fill weight for a 20 cm x 20 cm pack was 0.45 kg.

Respiration modeling of whole tomato at different temperatures for modified atmosphere packaging

Respiration rate of whole tomato was modeled at 10, 15 and 17 deg C using a closed respiration ch... more Respiration rate of whole tomato was modeled at 10, 15 and 17 deg C 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 mm low-density polyethylene (LDPE) or micro-perforated polypropylene (MPP) bags and stored at 10, 15 and 17 deg C. Measured O2 transmission rate (TrO2) for LDPE film followed Arrhenius kinetics with respect to temperature, ranging from 88 ml•m-2•h-1•atm-1 at 10 deg C to 144 ml•m-2•h-1•atm-1 at 17 deg C. TrO2 of MPP film was fairly constant regardless of temperature, with a range of 420.6 – 485.3 ml•m-2•h-1•atm-1. Modified atmospheres developed in the simulated packages compared well with predictions based on the uncompetitive inhibition model and measured film transmission rates. Predicted steady state O2 and CO2 levels in LDPE packages reached 3% and 4-6%; for MPP, predicted steady state conditions were 9-12% O2 and 8-13% CO2.

Good practice in the design, management and operation of a fresh produce packing-house

by Kevin Yaptenco and Rosa Rolle

Market oriented production trends across Asia and the Pacific region, spurred by growth in the fo... more Market oriented production trends across Asia and the Pacific region, spurred by growth in the food service, supermarket and export sectors, rising living standards and growing consumer awareness necessitate a shift toward improved handling practices in fresh produce supply chains. Within the post-harvest system, the packing-house serves as a control point where quality management can be applied to assure a reliable supply of produce of good quality. Packinghouses also serve as sites for the effective implementation of strategies designed to eliminate or minimize microbial, chemical and physical contamination.

Sugar Accumulation as a Mechanism for Freezing Tolerance in Cold-Stored 'Danshaku' Potato Tuber (Solanum tuberosum L.)

food preservation science, 2000

ABSTRACT Tissue samples from cold-stored (0°C) &#39;Danshaku&#39; potato tuber which unde... more ABSTRACT Tissue samples from cold-stored (0°C) &#39;Danshaku&#39; 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.

Property Changes in Potato Tubers (Solanum tuberosum L.) During Cold Storage at 0 and 10°C

food preservation science, 2000

Starch Gelatinization Kinetics in Cold-Stored 'Danshaku' Potato Tubers (Solanum tuberosum L.)

food preservation science, 2000

Optimized drying parameters of water hyacinths

The study investigated the optimum drying conditions of water hyacinth to contribute in the impro... more The study investigated the optimum drying conditions of water hyacinth to contribute in the improvement of present drying processes. The effects of independent parameters (drying temperature, airflow rate, and number of passes) on the responses were determined using the Response Surface Methodology. The response parameters were composed of (1) final moisture content, (2) moisture ratio, (3) drying rate, (4) tensile strength, and (5) browning index. Box and Behnken experimental design represented the design of experiments that resulted in 15 drying runs. Statistical analysis evaluated the treatment effects. Drying temperature significantly affected the drying rate, moisture ratio, and browning index. Airflow rate had a significant effect only on the drying rate, while the number of passes significantly affected both the drying rate and browning index. The optimized conditions for drying the water hyacinth were at drying temperature of 90ˆC, airflow rate of 0.044m 3 /s, and number of passes equivalent to five. The best model that characterizes the drying of water hyacinth is a rational function expressed as: