RESUMO
Fruit yield and quality of greenhouse tomatoes are strongly influenced by light conditions and nitrogen (N) availability, however, the interaction between these factors is still unclear. We evaluated the effects on cherry tomatoes of two tunnel plastic covers with different optical properties and three N doses, also in combination with a biostimulant treatment. We compared a diffuse light film (Film1) and a conventional clear film (Film2), and three N levels, corresponding to 50% (N50), 75% (N75) and 100% (N100) of the optimal dose, with and without a microbial plus a protein hydrolysed biostimulant, compared to a non-treated control. The three experimental treatments significantly interacted on several yield and quality parameters. In control plants (untreated with biostimulants), the early yield was higher at reduced N doses compared to N100, with greater increments under the diffusive Film1 compared to the clear Film2 (+57.7% and +37.0% vs. +31.7% and +16.0%, in N50 and N75 respectively). Film1 boosted the total fruit production at all the N rates and with or without biostimulants, compared to Film2, with stronger effects under sub-optimal N (+29.4% in N50, +21.2% in N75, and +7.8% in N100, in plants untreated with biostimulant). Total yield decreased with decreasing N levels, while it always increased with the application of biostimulants, which counterbalanced the detrimental effects of N shortage. Quality traits were mainly affected by the cover film and the biostimulant treatment. The diffusive film increased the content of carotenoids, lycopene and total phenols compared to the clear one, and the biostimulants increased texture, soluble solids, phenols and ascorbic acid compared to the untreated control. It is worth noting that in plants fertilized at 75% of the reference N dose, the biostimulants determined higher yield than the N100 untreated control, under both the covers (+48% in Film1 and +20% in Film2). In conclusion, the diffusive film improved the fruit yield and quality of greenhouse tomatoes in the spring-summer period, presumably avoiding plant stress due to high-intensity direct light. Reduced N rates limited the plant productivity, however, the biostimulant application was effective in compensating for the detrimental effects of sub-optimal supply of N synthetic fertilizers.
RESUMO
The use of two nozzle diameters (6 and 8 mm) in a cold (50°C) hemp seed oil extraction process was evaluated in terms of extraction efficiency, and chemical composition and in vitro fermentation characteristics of the residual cake. Seeds of the varieties Futura 75 and Uso 31 were pressed using a mechanical press with a cooling device. Five pressings were carried out for each variety and nozzle size, the functional parameters of the extraction processes were recorded, and sample of the residual cakes (n = 20) were analyzed. The 6 mm nozzle determined a higher oil yield (+4%) with a limited increase in temperature in the pressing chamber and in the oil (on average + 3°C compared to the 8 mm nozzle). A lower oil yield and consequently a higher fat content in the corresponding cake was observed when using the 8 mm nozzle. Despite the similar fat content, the two varieties had different oil yields and different residual cake compositions. The gas production kinetic of cakes was influenced by variety but little by nozzle size. Overall, the use of a smaller nozzle in a temperature-controlled extraction process can be a useful option to increase hemp oil yield while maintaining good fermentation characteristics of the residual cakes as ruminant feed.
