An insight into curcumin-based photosensitization as a promising and green food preservation technology

Consumer awareness on the side effects of chemical preservatives has increased the demand for natural preservation technologies. An efficient and sustainable alternative to current conventional preservation techniques should guarantee food safety and retain its quality with minimal side effects. Photosensitization, utilizing light and a natural photosensitizer, has been postulated as a viable and green alternative to the current conventional preservation techniques. The potential of curcumin as a natural photosensitizer is reviewed in this paper as a practical guide to develop a safe and effective decontamination tool for industrial use. The fundamentals of the photosensitization mechanism are discussed, with the main emphasis on the natural photosensitizer, curcumin, and its application to inactivate microorganisms as well as to enhance the shelf life of foods. Photosensitization has shown promising results in inactivating a wide spectrum of microorganisms with no reported microbial resistance due to its particular lethal mode of targeting nucleic acids. Curcumin as a natural photosensitizer has recently been investigated and demonstrated efficacy in decontamination and delaying spoilage. Moreover, studies have shown the beneficial impact of an appropriate encapsulation technique to enhance the cellular uptake of photosensitizers, and therefore, the phototoxicity. Further studies relating to improved delivery of natural photosensitizers with inherent poor solubility should be conducted. Also, detailed studies on various food products are warranted to better understand the impact of encapsulation on curcumin photophysical properties, photo-driven release mechanism, and nutritional and organoleptic properties of treated foods

Effects of dormancy breaking in stored seeds on germinability and seedling emergence of Tilia platyphyllos

Fruits of large-leaved lime dried to 10% may be stored for 16 years in sealed containers at –3°C without loosing seed viability. Dormancy of seeds, extracted from hard fruit coats, may be released after chemical scarification in concentrated sulphuric acid for 10 minutes, followed-by stratification without any medium (chilling) at the temperature of 3°C, for 20–24 weeks, i.e. until the first seeds start to germinate. After such pretreatment, during the germination test conducted at alternating temperatures 3~15°C (16 + 8 hours/day) seeds germinate near 90% in several weeks. For seedling production scarified and stratified seeds should be sown in early spring into trays under a plastic tunnel which ensures a high percentage of seedlings emergence. Sowing of the pretreated seeds in spring in a open nursery gives poor results

Effect of seed extraction, seed lot, and storage duration on germination capacity and seedling emergence of Alnus glutinosa (L.) Gaertner

Black alder, a major forest tree species in Europe, thrives in moist soils. During the seeds extraction (nutlets) from the cones, the heaviest seeds were observed to fall out first. Seed weight was not correlated to the ability of germination; no significant differences were observed between the heaviest and the lightest seeds. Seeds with a fresh mass moisture content of 8−9% after storage in –3°C retained their high germinability for six winters. However, seedling emergence decreased gradually when tested in cell trays in an unheated greenhouse. Along with the decline of seedling emergence, the participation of high seedlings (≥25 cm) decreased and participation of small seedlings increased simultaneously. These results question whether the practice of storing seeds in –3°C for long time is the best method of germplasm preservation

A vigour test for quality assessment of stored beech (Fagus sylvatica L.) nuts

Many seed lots of beech (Fagus sylvatica L.) nuts are characterized by various levels of infection with pathogenic fungi, such as Fusarium, Rhizoctonia and Cylindrocarpon spp. Favourable conditions for fungal infection of beechnuts are created especially during their long-term provisional storage without earlier drying to the moisture content of 8-10%. Strongly infected seed lots are not suitable for long-term storage. During the pre-sowing treatment of seeds by stratification without medium, fungi develop under the moist conditions and infect many healthy seeds. To assess the quality of beechnuts, a vigour test has been developed. Seeds removed from the pericarp (4 replications of 50 nuts each) are placed in boxes between two layers of moist tissue paper and incubated at 25°C for 120 hours. After this period decayed seeds (mouldy seeds) are excluded, and the remained are subjected to embryo viability by the tetrazolium test. When the percentage of decaying seeds (including those with necroses) does not exceed 10-15%, such seed lot can be used for long-term storage. If the percentage exceeds 50%, the seed lot should be considered unsuitable both for storage and for pre-sowing treatment, because only a very small proportion of seeds will emerge in the nursery

Seed storage, germination and seedling emergence in Rhamnus catharticus

This study was aimed to improve the understanding of germination ecology and to explain the invasive character of the common buckthorn (Rhamnus catharticus) in North America. Its fully mature seeds are characterized by a lack of dormancy. In laboratory conditions, favourable thermal conditions were identified for seed storage, germination and seedling emergence. At the cyclically alternating temperature of 20~30°C (16+8 h daily), seeds of this species showed a high germination rate within few weeks. Two other thermal variants, 3~15°C and 3~20°C (16+8 h daily), were much less effective for seed germination. However, cold stratification (at 3°C) in a moist mixture of peat and sand, lasting 4–8 weeks, caused a remarkable increase in germination rate also at 3~15°C. Seeds extracted from ripe fruits and dried (to a moisture content of about 10%) showed high germination and emergence rates after storage for 3.5 years at –3°C

Improving seed germination and seedling emergence in the Juniperus communis

The observed juniper decline, lack of natural regeneration, and disappearance of numerous populations of the common juniper in Poland, were the major reasons for initiation of research on its sexual propagation and seedling production. This study shows that seed dormancy in this species is broken by warm-cold stratification at 15°C/3°C, for 14+12 weeks, respectively. Seed drying for 72 h at room temperature in the middle of the warm phase (i.e. after 4–8 weeks of stratification at 15°C) and the following cold stratification at 3°C, cause a significant increase in seed germination capacity at cyclically alternating temperatures of 3~15°C, and in seedling emergence in growing trays (67 cells each) in a greenhouse. However, seedling emergence was over 2-fold to 4-fold lower in an open nursery than in the greenhouse. After sowing in the nursery, secondary dormancy was probably induced, because some seeds germinated in the following year. Some very young, 2-year-old seedlings started to produce male or rarely female cones. This study also showed that soil conditions of mother plants can influence the pattern of seed germination and seed ling emergence

Betula pendula seed storage and sowing pre-treatment: effect on germination and seedling emergence in container cultivation

Irregular seed crop in Betula pendula (Silver Birch) is a reason to create seed reserves, ensuring nursery production in years of crop failure. This study investigated the effects of seed moisture content and storage temperature on germinability and seedling emergence in container cultivation. Mature catkins were collected separately from 3 trees. The mixture of winged nuts and scales was dried to 3 levels of moisture content and stored at 3°C, –3°C and –10°C. After storage for 3, 5 and 6 years, the seeds were separated from scales and next dewinged and sorted in acetone into empty and filled seeds. Cleaned nuts were germinated in the Jacobsen germinator. Besides, to assess seedling emergence, seeds were sown on the surface of peat mixed with perlite, in multi-cell trays under a plastic tunnel. Significant differences in germinability were detected depending on the mother tree, seed moisture content and storage time. The viability of seeds stored at –10°C remained unchanged for 6 years regardless of moisture content (ca. 8–12%). Seeds stored at higher temperatures lost their germinability faster. An unexplained increase in seedling emergence was observed after extended seed storage at –10°C, in contrast to a gradual decrease in seedling emergence after extended storage at –3°C