The effectiveness of low temperature (5 °C) on Sitophilus oryzae (L.), Sitophilus zeamais (Motch.) and Sitophilus granarius (L.) in wheat grain: The impact of pre-acclimation

Laboratory trials were conducted in wheat grain to assess the effectiveness of low temperature (5 °C), applied at intervals of 5, 7, 9, 11, 20, 25, 30 and 35 days (d), as a control measure for stored product insect pests of the genus Sitophilus, and compared the results with the impacts of 7 d pre-acclimation at 15 °C and non-acclimation. Mortality was determined after 1, 2 and 7 d of recovery in the laboratory at 25 ± 1 °C and 60 ± 5% r. h., while progeny were assessed 7 weeks later. Acclimation had the strongest impact on S. oryzae after 5 d exposure to 5 °C and 7 d recovery, while the same effect on S. zeamais was shown after 20 and 25 d of exposure and 1 d recovery, and the same impact on S. granarius occurred after 30 and 20 d of exposure and 1 and 7 d recovery, respectively. Low temperature was found to be the most effective against S. oryzae, and the least effective against S. granarius. Mortality was high (≥96%) in both S. oryzae test groups after 11 d of exposure and 7 d recovery, S. zeamais mortality was high (>97%) after 35 and 30 d of exposure and 2 and 7 d of recovery, respectively, and S. granarius mortality was ≤87% in all test variants. Total reduction (100%) of non-acclimated S. oryzae, S. zeamais and S. granarius progeny required 8, 25 and 30 d of exposure to 5 °C, respectively, while acclimated weevils required 11, 30 and 30 d, respectively.     

Genetic diversity and its geographic structure in Sitophilus oryzae (Coleoptera; Curculionidae) across India – implications for managing phosphine resistance

The rice weevil, Sitophilus oryzae, is a serious global pest of stored grains. Fumigation with phosphine gas is the primary control method for S. oryzae, but the indiscriminate and prolonged use of phosphine gas has led to the development of heritable resistance. Developing and implementing an effective phosphine resistance management strategy for S. oryzae relies on an understanding of its genetic diversity and any structuring of that diversity geographically. We therefore sequenced the mitochondrial cytochrome c oxidase subunit I gene from 143 S. oryzae specimens collected from 37 locations across India, and from that assessed the genetic diversity of the species and its phylogeographic structuring. In addition, we compared the genetic diversity in Indian S. oryzae populations (the hypothesised origin of this beetle) to global populations. Genetic diversity was low in Indian S. oryzae, with only eight haplotypes (including two very common haplotypes) identified. The low level of mitochondrial diversity observed in this species appears typical of stored product pests, perhaps suggesting that low mitochondrial diversity is associated with repeated phosphine fumigations, which may eliminate low frequency haplotypes. The genetic diversity of S. oryzae in India is, however, higher than in many other countries, though comparable levels were identified in China. There was no evidence of population genetic structure across India, with most haplotypes found in three of the broad biogeographic regions. This lack of phylogeographic structuring indicates significant gene-flow across India, most likely through the incidental anthropogenic transport of this relatively poor (or reluctant) flyer. The major practical implication is that phosphine resistance management for S. oryzae needs to be dealt with country wide, as populations are not isolated.     

The efficacy of different surface applications of wettable powder formulation of Detech® diatomaceous earth against the rice weevil,Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

In this study, the insecticidal activity of the wettable powder formulation of Detech® diatomaceous earth against the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), an important stored grain pest, was investigated. Detech® diatomaceous earth was applied on concrete and wooden surfaces at doses of 0.25, 0.5, 1 and 2 g/m² and the mortality of S. oryzae adults was observed at time intervals of 24, 48, 72, 96, 120, 144, 168, 192, 216, 240, 264 and 288 h. In the first 24 h of application on the concrete and wooden surfaces, no death was observed. At the 48^th hour, no effect or very low mortality was observed on the concrete and wooden surface at all doses. While the increase in dose and exposure time on the concrete and wooden surface increased the mortality rate of the adults, complete adult mortality was obtained on concrete surfaces after 288 h. The wettable powder formulation of Detech® diatomaceous earth at a dose of 2 g/m² is highly effective against rice weevils on wood and concrete surfaces at laboratory conditions, though with greater success on concrete, but the longer DE exposures increase the efficacy on both surfaces.     

Apparent voluminosity of casein micelles in the temperature range 35–70 °C

Casein micelles are basic units of dairy matrices that can be aggregated by reducing their electrostatic repulsion or by surface modifications. Studying casein micelles in terms of a colloidal suspension demands of a preferably complete physico-chemical characterisation. Process control in dairy technology as well as mechanistic models that explain the formation and structure of dairy products build on the specific hydration of the casein micelles. The effect of the temperature on the voluminosity of native casein micelles at pH 6.6–6.7 was investigated using rheometry covering a wide range of temperatures and mass fractions. Increasing temperature resulted in a constant decrease of the voluminosity up to 70 °C. A quadratic polynomial was tested to fit the temperature dependency the best. The apparent voluminosity of casein micelle suspensions was determined with 4.0 mL g⁻¹ at 35 °C, 3.6 mL g⁻¹ at 50 °C, and 3.5 mL g⁻¹ at 70 °C.     

Combined high pressure-mild temperature processing for optimal retention of physical and nutritional quality of strawberries (Fragaria × ananassa)

Response surface methodology was used to determine the optimal high pressure-temperature condition for the processing of strawberries for maximal inactivation of oxidative enzymes as well as best retention of nutritional and physicochemical quality following processing and during storage. High pressure treatment at 20–40 °C resulted in visual quality closest to the fresh product. High pressure combined with mild temperature caused substantial inactivation of peroxidase in strawberries with a maximum of 58% inactivation after 10 min treatment at 600 MPa and 60 °C. No significant inactivation of polyphenol oxidase was observed in strawberries under the studied condition. Combined high pressure-mild temperature processing did not have significant effect on the total polyphenol and total anthocyanin content of strawberries. However, an average of 22 ± 13% loss of total polyphenol content and 27 ± 10% loss of total anthocyanin contents was observed after 3 months of refrigerated storage.Industrial relevanceThe work described in this research is relevant to the high pressure processing of strawberries and other berry fruits. The results of the study have shown that best quality retention of strawberry products is obtained when high pressure processing is combined with vacuum packaging in high barrier packaging material and refrigerated storage since strawberry polyphenol oxidase is highly resistant to high pressure inactivation.     

Commercial peppermint (Mentha × piperita L.) teas: Antichlamydial effect and polyphenolic composition

The qualitative and quantitative polyphenolic contents in the infusions of the commercial peppermint tea (Mentha × piperita L.) samples (n = 27) from different countries were studied using HPLC–UV-MS/MS analysis. The most abundant polyphenolics in the peppermint infusion were eriocitrin, 12-hydroxyjasmonate sulfate, luteolin-O-rutinoside and rosmarinic acid. In order to evaluate the content of samples by finding chemosystematic markers, the essential oil composition was studied by GC. The analyses showed that the 24 (89%) peppermint tea samples contained peppermint, whereas three samples may contain Mentha spicata, different from that claimed on the package.The effects of seven peppermint tea extracts against respiratory tract pathogen Chlamydia pneumoniae were investigated in vitro. All seven selected tea extracts were active against C. pneumoniae, the growth inhibition ranging from 20.7% to 69.5% at extract concentration of 250 μg/ml. In most cases, the antichlamydial activity was related to the peppermint teas having also high content of luteolin and apigenin glycosides. This study supports the consumption of peppermint tea to potentially elicit beneficial health effects on acute respiratory tract infections.     

Combined natural antimicrobial treatments (EDTA,lysozyme, rosemary and oregano oil) on semi cooked coated chicken meat stored in vacuum packages at 4 °C: Microbiological and sensory evaluation

The present study examined the effect of natural antimicrobials: Ethylenediaminetetraacetate (EDTA), lysozyme, rosemary and oregano oil and their combinations, on the shelf-life of semi cooked coated chicken fillets stored under vacuum packaging (VP), at 4 ± 0.5 °C for a period of 18 days. The treatments of semi cooked coated chicken fillets examined in the present study were the following: Air-packaged (A, control samples), vacuum-packaged (VP), VP with EDTA–lysozyme solution 1.50% w/w, (VP + EL), VP with rosemary oil 0.20% v/w, (VP + R), VP with oregano oil 0.20% v/w, (VP + O), VP with EDTA–lysozyme solution and rosemary oil (VP + EL + R) and finally VP with EDTA–lysozyme and oregano oil (VP + EL + O). The shelf-life of the samples was determined using both microbiological and sensory analyses. Among the antimicrobial combinations examined in the present study, the treatments VP + EL + R and VP + EL + O were the most effective against the growth of Gram-negative, Gram-positive bacteria, and to a lesser extent on yeasts. Based on both microbiological (TVC data) and sensory (taste attribute) analyses, treatments: VP and VP + O gave a shelf life extension of 6 days, whereas treatments VP + EL + R and VP + EL + O produced a shelf-life extension of 7–8 days, as compared to the control samples.Industrial RelevanceThe present research has highlighted the use of natural antimicrobial treatment combinations, including: EDTA, lysozyme, rosemary and oregano oil and their combinations, in the extension of shelf-life of semi cooked coated chicken fillets stored under vacuum packaging at 4 °C for a period of 18 days. Establishing, the determination of the shelf-life of fresh poultry and products represents a challenge for food companies as poultry meat has a short shelf-life, which causes substantial practical problems for its distribution. Therefore, knowledge of natural preservatives, that can be used as alternatives to chemical additives, that could extend the products' shelf life can have an important economic feedback by reducing losses attributed to spoilage and by allowing the products to reach distant and new markets. This study has shown that combinations of natural antimicrobials can extend the shelf-life of the product.     

Changes in quality attributes of pulsed light and thermally treated mixed fruit beverages during refrigerated storage (4 °C) condition

The effect of batch pulsed light (PL) irradiation (3000 J cm⁻²) on the shelf-life of the beverage blend comprising apple ber (Indian jujube), carambola (star fruit), and black table grapes was investigated. The equivalent thermally treated beverage (90 °C|5 min) exhibited greater stability from microbial and enzymatic spoilage but retained 27% less antioxidants and 14% less vitamin C than PL-treated juice. Thermally and PL-treated blends possessed sensory scores of 5.8 and 7.2, respectively. The beverage's microbial shelf-life (population ≤ 6-log₁₀ cfu/mL) was extended to 45 days at 4 °C after the PL treatment. The PL exposure did not alter the pH and soluble solids during storage. The PL-treated juice, after 45 days, was placed on par with the freshly prepared juice by the sensory panel. The PL-treated juice preserved 61% more antioxidants, 38.8% more phenolics, and 68.2% more vitamin C than the thermally pasteurized beverage after 45 days of refrigerated storage.Industrial relevanceWhile the fruit processing industry demands microbial safety and enzymatic stability, today's consumer demands juices of high nutritional quality. This study utilizes under-explored fruits like apple ber (Indian jujube) and carambola (star fruit) to make a shelf-stable mixed fruit beverage. This study will help the industry understand the potential of PL treatment in accomplishing microbial safety, enzymatic stability, and nutritional quality, along with the utilization of under-explored fruits.     

Physical factors in the hermetic SuperGrainBag® and effect on the larger grain borer [Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)] and aflatoxin production by Aspergillus flavus during the storage of ‘Obatanpa’ maize (Zea mays L.) variety

Controlling invasive pests and aflatoxin production by moulds in stored grains is a global challenge to food security and public health, particularly in Africa. Food storage systems are designed to provide constraints to spoilage organisms by presenting mechanical barrier or unfavourable atmospheric conditions to their growth and productivity. This study examined the physical factors generated in hermetic SuperGrainBags^® during the storage of ‘Obatanpa’ variety of maize (Zea mays L.) and the effect on growth of the larger grain borer Prostephanus truncatus (Horn) and aflatoxin contamination by Aspergillus flavus. Cultured P. truncatus or A. flavus was introduced into 1.5 kg of the dried maize and stored in either hermetic SuperGrainBags^® or non-hermetic polypropylene bags. The hermetic conditions elicited an increase in the interstitial temperature (ca. 27 °C) but a decrease in the relative humidity (<70%), oxygen concentration (<6.4%) and the grain moisture content (<13.7%), the combined effects of which inhibited growth of the insects and aflatoxin production by the moulds. Total mortality of P. truncatus occurred after 52 d of storage in the SuperGrainBags^® while aflatoxins concentration remained within safe limits for human consumption. In contrast, there was proliferous growth of P. truncatus and significant increase in aflatoxin concentration to lethargic levels within the polypropylene bags where temperature, relative humidity and grain moisture increased significantly. Accordingly, grain damage and weight loss percentages were significantly high in the polypropylene bags while that in the SuperGrainBags^® were negligible. Altogether, the SuperGrainBags^® better preserved the maize grain quality and safeguarded it against health risks than the polypropylene bags.     

Changes of microbial diversity and volatile compounds in edible and deteriorated Qingke barley fresh noodles stored at 25 °C

Microbial diversity and volatile compounds in Qingke barley fresh noodles (QBFN) with different storage time at 25 ± 1 °C were investigated. The results showed that Pseudomonas, Pantoea, Erwinia and Alternaria, Pyrenophora, Penicillium were the dominant microorganisms in edible QBFN (stored for 0 and 12 h), while Pantoea, Erwinia, Bacillus and Penicillium, Aspergillus were the dominant spoilage microorganisms in deteriorated QBFN (stored for 18 h). The edible QBFN have high concentration of aldehydes (61.27 μg kg⁻¹), furan and pyrazines (60.87 μg kg⁻¹), alcohols (49.74 μg kg⁻¹) and ketones (29.74 μg kg⁻¹) that give basic flavours to the QBFN. As storage time increased, the concentrations of above volatile compounds decreased, and new esters and sulphuric compounds which gave unpleasant odours to the QBFN appeared. Multivariate data analysis methods showed that 2-pentyl-furan, hexanal, 5-Ethylcyclopent-1-enecarboxaldehy, cyclohexanol and methyl allyl sulphide, ethyl isovalerate were the main volatile compounds that make a difference in flavour between the edible and deteriorated QBFN.     

Predicting Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) populations and associated grain damage in smallholder farmers’ maize stores: A machine learning approach

Prostephanus truncatus is a notorious pest of stored-maize grain and its spread throughout sub-Saharan Africa has led to increased levels of grain storage losses. The current study developed models to predict the level of P. truncatus infestation and associated damage of maize grain in smallholder farmer stores. Data were gathered from grain storage trials conducted in Hwedza and Mbire districts of Zimbabwe and correlated with weather data for each site. Insect counts of P. truncatus and other common stored grain insect pests had a strong correlation with time of year with highest recorded numbers from January to May. Correlation analysis showed insect-generated grain dust from boring and feeding activity to be the best indicator of P. truncatus presence in stores (r = 0.70), while a moderate correlation (r = 0.48) was found between P. truncatus numbers and storage insect parasitic wasps, and grain damage levels significantly correlated with the presence of Tribolium castaneum (r = 0.60). Models were developed for predicting P. truncatus infestation and grain damage using parameter selection algorithms and decision-tree machine learning algorithms with 10-fold cross-validation. The P. truncatus population size prediction model performance was weak (r = 0.43) due to the complicated sampling and detection of the pest and eight-week long period between sampling events. The grain damage prediction model had a stronger correlation coefficient (r = 0.93) and is a good estimator for in situ stored grain insect damage. The models were developed for use under southern African climatic conditions and can be improved with more input data to create more precise models for building decision-support tools for smallholder maize-based production systems.     

Olfactory host location and host preference of Holepyris sylvanidis (Brèthes) (Hymenoptera: Bethylidae), a parasitoid of Tribolium confusum Jacquelin du Val and T. castaneum (Herbst) (Coleoptera: Tenebrionidae)

Parasitoids can suppress populations of their host and thus play a primary role in Integrated Pest Management. We studied foraging cues in Holepyris sylvanidis (Hymenoptera: Bethylidae), a larval parasitoid of Tribolium species, in a four-chamber olfactometer. H. sylvanidis is reported as a cosmopolitan parasitoid of Coleopteran including two major pests of stored products, the confused flour beetle Tribolium confusum and the red flour beetle T. castaneum. Our study reveals that the host complexes of both Tribolium species and different living host stages attract naive H. sylvanidis females, whereas no reaction was observed to uninfested substrates. Our findings may contribute to the development of biological control strategies of T. castaneum and T. confusum with parasitoids.     

Phytochemical composition,health effects,and crop management of liquorice (Glycyrrhiza glabra L.): Α medicinal plant

Liquorice has been widely appreciated as an important medicinal plant. Its rhizomes and roots have been used for centuries in traditional medicine due to their renowned therapeutic properties. However, increasing market demands and irrational harvesting of wild liquorice plants has rendered the cultivation of the species of major importance. This review presents aspects related to chemical composition and health effects of the species, and the effect of various cultivation practices. Particular interest is given on glycyrrhizin and its extraction procedures, since it is the main bioactive compound of liquorice roots and its content determines the final product quality.     

Combined effects of heating and γ-irradiation on the microbiological and sensory characteristics of Gochujang (Korean fermented red pepper paste) sauce during storage

This study was conducted to evaluate the combined effect of heating and γ-irradiation on the microbiological and sensory characteristics of gochujang sauce. Gochujang sauces could be sterilized by heating (HT: 121°C for 15 min) or γ-irradiation (IR: 30 kGy), but their sensory qualities were severely decreased. Otherwise, the combined treatment of heat and γ-irradiation could minimize the change of sensory qualities. Combination treatment of γ-irradiation at 17.5 kGy after heating at 100°C for 30 min (HT-IR) would be optimal. During storage the gochujang sauce samples then were analyzed to enumerate total bacterial populations, to measure pH, and Hunter’s color values, and for sensory evaluation. Any growth of total bacterial populations was not observed in HT, IR, and HT-IR (detection limited 1< log CFU/g). The pH values of gochujang sauce ranged from 4.57 to 4.75 during storage. The Hunter’s (L*, a*, and b*) values of gochujang sauce were gradually decreased during storage, regardless of treatment. Sensory characteristics and acceptance of HT and IR were significantly lower (p<0.05) than those of non-treated control and HT-IR, but there was no difference (p⩾0.05) among non-treated control and HT-IR.     

Effect of temperature and pH on the solubility of caseins: environmental influences on the dissociation of α(S)- and β-casein

Selective precipitation is a common method for the isolation of β-casein, using the different calcium sensitivities of the individual caseins and the selective solubility of β-casein at a low temperature. In previous studies, it has been indicated that the β-casein yield depends on the physicochemical characteristics of the casein raw material used for fractionation. The objective of this study was to evaluate and compare the solubility of α(S)- and β-casein in solutions of micellar casein, sodium caseinate, and calcium caseinate as a function of pH and temperature. Additionally, the solubility of isolated α(S)- and β-casein fractions in demineralized water, ultrafiltration permeate, and a calcium-depleted milk salt solution was investigated depending on the pH and temperature. Furthermore, micellar casein, sodium caseinate, and calcium caseinate were subjected to a calcium chloride-precipitation process to determine the solubility of α(S)- and β-casein in calcium chloride precipitate, which is produced during selective precipitation, as a function of temperature and pH. Generally, the temperature had only a marginal influence on the α(S)-casein solubility compared with the β-casein solubility, whereas the solubility was shown to be strongly influenced by the pH. Our results suggest that the yield of β-casein obtained during isolation by means of selective precipitation may be a result of the solubility characteristics of α(S)- and β-casein in calcium chloride precipitate. Manufacturers may consider a simple solubility experiment before the β-casein isolation process by means of selective precipitation to predict β-casein yield.