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October-December 2017 Issue (Vol. 19 No. 4)

by Patrick Raymund A. Lesaca

Chemical residues from pesticides and fertilizers, including heavy metals, have been implicated to have toxic effects on humans and are detrimental to soil ecology. Food-borne microbial pathogens are believed to be the most frequently occurring hazard in the nation’s food and water which could be originating from the farm itself especially if organic fertilizers used were not properly processed. Costeffective interventions are necessary to prevent, control, or eliminate microbial pathogens on fresh and minimally-processed food products.

Food quality and safety evaluation of organic food products should include not only physico-chemical and residue analysis, but also assessment of potential microbiological hazards both in organically-grown and conventionally-grown produce.

A group of researchers from the Institute of Molecular Biology and BiotechnologyUniversity of the Philippines Los Baños (BIOTECH-UPLB) conducted a project study to evaluate the food quality and safety of organically-grown and conventionally-grown crops in two types of soil; and assess the crops in terms of their chemical contaminants and incidence of microbial pathogens. The project was intended to validate the presence of microbial pathogens in the edible portions of organically-grown crops, and assess the quality of soil after two years of growing crops in conventional method compared with organic agriculture practices.

The study, “Food Quality and Safety Evaluation of Organically Grown Crops Versus Conventionally Grown Crops in Two Types of Soil” was funded by the Bureau of Agricultural Research and led by Dr. Lorele C. Trinidad of UPLB-BIOTECH. The premise of the study lies on the observation that, no available up-to-date information on the extent or level of contaminants present in organic and conventional produce (both chemical and microbiological) that could support or refute the claim that organicallygrown produce are more or less chemically and microbiologically safer than the conventionally-grown produce. Hence, investigation of the chemical and microbial qualities of both the organically-grown and conventionally-grown produce must be done to ensure safety of the consumers and of the general public.

Specifically, the objective of the study aimed to assess the food safety of conventionally-grown versus organically-grown crops in terms of chemical contaminants (heavy metals and pesticides) and incidence of microbial pathogens (Salmonella and E.coli). The study involved two problem soil types: acidic and clay types in the uplands of Majayjay, Laguna; and in the lowland lahar-laden soil of Bacolor, Pampanga.

A site was established in Brgy. Bitaoy, Majayjay, Laguna for management of conventional agricultural practice and for planting of organic crops. Selected crops including lettuce, cucumber, tomato, and bell pepper were planted. Meanwhile, in the lowlands of Bacolor, Pampanga the soil is lahar-laden, thus, amendment with compost and coco coir was necessary to increase its water absorption and holding capacity. Levels of Nitrogen (N), Phosphorus (P), Potassium (K) and organic matter content were also initially increased. Heavy metals such as lead, copper, zinc, chromium, cadmium, mercury, manganese, titanium were monitored in soil through X-ray florescence (XRF) spectrometry, a non-destructive analytical technique used to determine the elemental composition of materials. The selected crops planted were ampalaya, okra, eggplant, and stringbeans.

Both sites were evaluated for chemical and microbial analyses, and partial reports conducted by the team of researchers yielded the following observations: There was an inconsistent trend in the N, P, K level and organic matter content of the soil after harvest due to the occurrence of typhoons and floods, which may have washed out a significant amount of surface soil. A year or two was not sufficient to determine significant change in the soil quality due to organic or conventional farming system. A much longer time is recommended for this kind of study considering also the seasonal fluctuations.

The microbial population in soil and the edible portions of harvested crops was analyzed using standard methods. Presence of microbial pathogens such as E. coli O157:H7 and Salmonella was also monitored after harvest. Actinomycetes are the most abundant bacteria in stable soils, yet, they are rarely reported on vegetable products. On the other hand, lactic acid bacteria are rarely found in soil per se, but they are significant parts of the bacterial biota of plants and plant products. The prevalence of microbial pathogens in some of the vegetable samples may be due to the improper processing of chicken manure and other organic wastes used as compost. Salmonella and E. coli are enteric microorganisms usually found in the intestinal tract of animals. Edible portions of the crop may be contaminated with the mentioned bacteria through contact with the compost or with the contaminated soil.

Other than determining chemical contaminants and incidence of microbial pathogens, the project also geared toward the development of technologies for maintaining the quality and ensuring the safety of organicallygrown fruits and vegetables during harvesting, postharvest handling, storage and marketing.

Postharvest technology researches focused on: 1) determining safety of the produce from microbial contaminants (determination of chemical or pesticide contaminants was not included) along the various points in the supply chain; 2) physicochemical characterization and determination of quality changes of organically-grown produce, which were also compared with conventionally-grown counterparts; 3) maintaining the freshness of the produce and extending shelf-life (Modified Atmosphere Packing, organic acids for disease control, packaging, ripening); and 4) minimizing postharvest disease.

The results, in the form of new information or technology protocols, generated from the research studies were then translated to information education and communication materials (IEC) and disseminated and shared with the actors, both the direct and indirect players of the organic fruit and vegetables supply chain namely, the growers or organic practitioners, agricultural technicians, fellow researchers and other industry players.

Eight awareness training or capability building programs on postharvest handling of organically-grown fruits and vegetables were provided to organic practitioners in response to the needs of the industry. Most of these were in cooperation with the municipal LGUs through the agriculture office. One training program was conducted with Alter Trade Corporation, the project cooperator in the conduct of postharvest research on organic banana. A training manual was also prepared based on the training programs conducted. Evaporative cooler crates and an upscale design were provided by the project to selected vegetable producers and traders, and growers’ association, who also served as cooperators of the project.

While there were a number of postharvest researches conducted during the project duration, more researches are still needed to be done on organic fresh fruits and vegetables. The changing climate greatly affected the organic production and consequently, the availability of supply became the limiting factor in the conduct of research during the span of the project. Moreover, other organic production systems in Luzon and outside of Luzon area, and the many other types of fresh fruits and vegetables grown organically have yet to be studied.

Several factors can affect the nutritional quality of crops and a well-designed and controlled study is necessary to be carried out. It has been pointed out that, to carry out a valid comparison between organic and conventional food products, it is required that plants should be cultivated in similar soils and under similar climatic conditions. To obtain representative results, it is recommended that the same crop is repeated several times throughout a long-term study. ###

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Contact details: Dr. Lorele C. Trinidad BIOTECH-UPLB College, Los Baños, Laguna phone: (049) 536-1620 email: This email address is being protected from spambots. You need JavaScript enabled to view it.

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