Effects of defect action level of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) fragments on quality of wheat flour.

BACKGROUND: Tribolium castaneum (Herbst) is one of the most important secondary storage pests of all types of flour and flour-based products. The present study focuses on the fragment producing behaviour of T. castaneum in wheat flour during storage and its effect on the quality parameters and defect action level (DAL) of fragments. The US Food and Drug Administration has set a DAL of 75 insect fragments in 50 g of flour. Box-Behnken design was used to optimize the storage conditions (storage period in days and temperature in degrees Celsius) and insect density (numbers) to keep insect fragments below the DAL. RESULTS: Optimization results indicated that the presence of single number of adult of T. castaneum is enough to cross the DAL of insect fragments within a storage period of 21 days at a storage temperature of 30 °C. Insect fragments cause perceptible changes in the quality of wheat flour. When sample attained DAL of T. castaneum fragments in wheat flour,the various quality parameters were analysed in that moisture content of wheat flour was 10.8 ± 0.26%, total colour change was 2.052 (ΔE value), T. castaneum progeny emergence was 19.66 ± 1, uric acid was 1.8 ± 0.16 g kg-1 and microbial count was 7.34 ± 0.5 cfu g-1 . CONCLUSIONS: Results from the present study indicate that the presence of even a single adult of stored pest in wheat flour should not be ignored. It is mandatory to determine the threshold level and frequent sampling is required to achieve zero tolerance of stored product insects in food commodities. © 2021 Society of Chemical Industry.

A Molecular Approach for the Detection and Quantification of Tribolium castaneum (Herbst) Infestation in Stored Wheat Flour.

RESEARCH BACKGROUND: The presence of insect fragments is one of the major constrains in stored food commodities and it causes considerable loss in the quality of the produce. The management of the pest is viewed as a huge challenge in foodprocessingindustry. Conventionally, the detection of Tribolium castenaum in the food processing industry is carried out by acid hydrolysis and staining methods that are time consuming and lack precision. EXPERIMENTAL APPROACH: Considering the importance of a quick and effective method, a quantitative polymerase chain reaction (qPCR)-based approach was developed and elucidated in this study. The mitochondrial cytochrome oxidase I (mtCOI) gene was identified as a target due to its abundance in the pest. Specific primers were designed against the target gene by Primer Premier software and amplified in a qPCR. RESULTS AND CONCLUSIONS: This method is capable of detecting all the ontogenic stages of T. castaneum in stored wheat flour. Earlier experiments had demonstrated that about 20 µg of DNA can be obtained from 2.2 mg of insects. To quantify the infestation levels, the cycle threshold (Ct) values obtained from known samples were subjected to regression analysis and expressed as adult equivalents. In the unknown samples, the infestation was calculated as 1.74 and 0.046 adult insects in 5 g of wheat flour. The maximum permissible limit of insect fragments in flour is 75 insect fragments or approx. 3 adults per 50 g of flour as per the US Food and Drug Administration (FDA). Hence, by adopting this new method, it is possible for the warehouse operators to arrive at a decision to proceed with efficient management practices where wheat flour is stored. Also, this method can be ratified by government agencies associated with international business to ascertain whether the wheat flour meets the standards set by the respective country before subjecting to foreign trade. NOVELTY AND SCIENTIFIC CONTRIBUTION: This study is the first of its kind in the detection and quantification of T. castaneum in milled products. So far, only conventional methods have been employed to assess the presence of the pests and manual counting of fragments are practiced to quantify the infestation levels. The developed qPCR method is faster, reliable and can be employed in milling industries, bakery industries, food processing plants and foreign trade units for critical detection and quantification of T. castaneum pest infestation.

Comparative laboratory efficacy of novel botanical extracts against Tribolium castaneum.

BACKGROUND: Citrus sinensis, Allium sativum, Ocimum basilicum, Mentha spicata, Curcuma longa, Carica papaya, Andrographis paniculata, Azadirachta indica, Cymbopogon citratus and Acorus calamus were compared in the form of extracts of chloroform, hexane and aqueous media for their effectiveness in repelling Tribolium castaneum. Filter paper of 9 cm in diameter was cut into halves. Using a micro-pipette, each extract was applied to one half of the filter paper. The volume applied was kept constant at 0.6 mL per 30 cm2 . The filter paper was dried and reattached leaving a 0.5 cm gap between, in a Petri-plate. Ten adults of T. castaneum were introduced and the repellency was observed after 30, 60 and 180 min. RESULTS: The aqueous extract of C. papaya exhibited the highest repellency (82-97%) followed by that of garlic bulbs (aqueous extract) with 86.67% repellency. Further, gunny bags were sprayed separately using bottle sprayers with the two most effective extracts at a constant volume of 42 mL per 575 cm2 . These treated gunny bags were compared with malathion-treated gunny bags in the insect management unit. The observations were taken after 2, 8 and 24 h. Papaya leaf extract-treated gunny bags showed relative repellent activity similar to that of malathion-treated gunny bags after 24 h of treatment. Thus, gas chromatography-mass spectrometry analysis of aqueous extract of papaya leaves was performed. CONCLUSIONS: It can be concluded that extract of papaya leaves containing 2-methoxy-4-vinylphenol (8.47% peak area) can be used as a repellent biopesticide. © 2019 Society of Chemical Industry.