Effects of light intensity and temperature on Cylindrospermopsis raciborskii (Cyanobacteria) with straight and coiled trichomes: growth rate and morphology

Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju (Ordem Nostocales) is one of the most troublesome bloom-forming species in Brazil. Understanding the population dynamics of the different morphotypes of C. raciborskii (straight and coiled) could assist in the prediction of favourable conditions for the proliferation of this potentially toxin-producing species. The aim of the present study was to assess the effects of two different light intensities and temperatures on the growth rate and morphology of the trichomes of the straight and coiled morphotypes. For such, two non-toxin producing strains of C. raciborskii were used - one with a coiled trichome (ITEP31) and another with a straight trichome (ITEP28). The strains were cultured in BG-11 medium in a climatic chamber under controlled conditions. Two light intensities (30 and 90 mu mol.m(-2).s(-1)) were combined at temperatures of 21 and 31 degrees C and the growth rate and morphological changes were analysed. The morphotypes responded differently to the different temperatures and light intensities. Both strains exhibited faster growth velocities when submitted to higher light intensity and temperature. The lower temperature and higher luminosity hampered the development of both strains. Variations in cellular morphology and an absence of akinetes in both strains were related to the lower temperature (21 C). The coiled morphotype demonstrated considerable phenotype plasticity, changing the morphology of trichome throughout its growth curve. Although molecular analysis does not sustain the separation of the morphotypes as distinct species, their different eco-physiological responses should be considered further knowledge of extreme importance for the population control of these potentially toxic organisms.CNPQ [Proc. 300794/2004-5, 500704/2004-0]FAPESP [Proc. 2004/00939-6, 2007/57509-1

PHYSICAL-CHEMICAL AND SENSORIAL QUALITY OF IRRADIATED AND MINIMALLY PROCESSED PINEAPPLE

The present work had as objective to monitor the physical-chemical and sensorial quality of pineapple cv. "Smooth Cayenne" minimally processed and submitted to gamma radiation. The fruits were peeled, sliced and sanitized with 20 mg.L-1 active chlorine. The slices were packed in polystyrene trays covered with vinyl polichloride flexible film (VPC) and irradiated with 1 and 2 kGy, being the control non irradiated. The samples were stored at temperature of 5 ±1oC and evaluated in the first, third and sixth days of storage for color, firmness, soluble solids (SS), total titratable acidity, pH and sensorial analysis. The control presented the smallest values of acidity and pH maintenance in all evaluations, while the soluble solids was higher in the first evaluation for the doses of 1 and 2 kGy, declining with storage time. The irradiation didn’t affect the color of minimally processed pineapples in the period of the evaluation, although reduced the firmness of the samples in the dose of 1 kGy. The control presented the best grades in sensorial evaluations for the attributes of aroma, taste, texture and appearance. In a general way, the best results were observed for non irradiated minimally processed pineapple (control), being that the irradiated samples with 1 kGy obtained inadequate results for the analysis of soluble solids, total titratable acidity, pH, firmness and sensorialO presente trabalho teve como objetivo monitorar a qualidade físico-química e sensorial de abacaxi cv. ‘Smooth Cayenne’ minimamente processado e submetido à radiação gama. Os frutos foram descascados, fatiados em rodelas e sanificados com 20 mg.L-1 de cloro ativo. As fatias foram acondicionadas em bandejas de poliestireno recobertas com filme flexível de policloreto de vinila (PVC) e irradiadas com 1 e 2 kGy, sendo o controle não-irradiado. As amostras foram armazenadas a temperatura de 5±1ºC e avaliadas no primeiro, terceiro e sexto dias de armazenamento quanto à coloração, firmeza, sólidos solúveis (SS), acidez total titulável (ATT), pH e análise sensorial. O controle apresentou os menores valores de acidez e manutenção do pH em todas as avaliações, enquanto que o teor de sólidos solúveis foi maior na primeira avaliação para as doses de 1 e 2 kGy, decaindo com o decorrer do período de armazenamento. A irradiação não afetou a coloração dos abacaxis minimamente processados no período de avaliação, porém reduziu a firmeza das amostras na dose de 1 kGy. O controle apresentou as melhores notas nas avaliações sensoriais para os atributos aroma, sabor, textura e aparência. De maneira geral, os melhores resultados foram observados para o abacaxi minimamente processado não-irradiado (controle), sendo que as amostras irradiadas com 1 kGy obtiveram resultados inadequados para as análises de sólidos solúveis, acidez total titulável, pH, firmeza e sensorial

Mechanical properties of pea starch films associated with xanthan gum and glycerol

The aim of this study was to evaluate the effect of the addition of xanthan gum and glycerol to the starch of green pea with high content of AM (cv. Utrillo) in the preparation of films and their physical characteristics. Filmogenic solution (FS) with different levels of pea starch (3, 4, and 5%), xanthan gum (0, 0.05, and 0.1%), and glycerol (glycerol-starch ratio of 1: 5 w/w) were studied. The FS was obtained by boiling (5 min), followed by autoclaving for 1 h at 120 degrees C. The films were prepared by casting. Films prepared only with pea starch were mechanically resistant when compared to other films, prepared with corn, cassava, rice, and even other pea cultivars (yellow, commercial). The tensile strength of these films is comparable to synthetic films prepared with high-density polyethylene and linear low-density polyethylene. However, they are films of low elasticity when compared to other films, such as rice starch films, and especially when compared to polyethylene films. The increased concentration of starch in the solution increased the puncture force. The increased concentration of glycerol slightly decreased the film crystallinity and interfered in the mechanical properties of the films, causing reduction of the maximum values of tensile strength, strain at break, and puncture force. The plasticizer also caused an increase of elongation at break. Xanthan gum was important to formation of films; however, it did not affect their mechanical properties