Long-term storage effect on chemical composition, nutritional value and quality of Greek onion landrace “Vatikiotiko”

Polyhydroxyalkanoate Production from Fruit and Vegetable Waste Processing

Traditional plastics represent a tremendous threat to the environment because of increases in polluting manufacturing as well as their very extended degradation time. Polyhydroxyalkanoates (PHAs) are polymers with similar performance to plastic but are compostable and synthesizable from renewable sources and therefore could be a replacement for fossil-based plastics. However, their production costs are still too high, thus demanding the investigation of new and cheap substrates. In this sense, agricultural wastes are attractive because they are inexpensive and largely available. Specifically, fruit and vegetables are rich in sugars that could be fermented into PHAs. In this work two strains, Cupriavidus necator DSM 545 and Hydrogenophaga pseudoflava DSM 1034, well-known PHA-producing microbes, were screened for their ability to grow and accumulate PHAs. Ten different fruit and vegetable processing waste streams, never before reported in combination with these strains, were tested. Residues from red apple and melon were found to be the most suitable feedstocks for PHA production. Under specific selected conditions, C. necator DSM 545 accumulated up to 7.4 and 4.3 g/L of 3-hydroxybutyrate (3HB) from red apple and melon, respectively. Copolymer production was also obtained from melon. These results confirm the attractiveness of food processing waste as a promising candidate for PHA production. Ultimately, these novel substrates draw attention for future studies on process optimization and upscaling with C. necator.

The Beneficial Health Effects of Vegetables and Wild Edible Greens: The Case of the Mediterranean Diet and Its Sustainability

The Mediterranean diet (MD) concept as currently known describes the dietary patterns that were followed in specific regions of the area in the 1950s and 1960s. The broad recognition of its positive effects on the longevity of Mediterranean populations also led to the adoption of this diet in other regions of the world, and scientific interest focused on revealing its health effects. MD is not only linked with eating specific nutritional food products but also with social, religious, environmental, and cultural aspects, thus representing a healthy lifestyle in general. However, modern lifestyles adhere to less healthy diets, alienating people from their heritage. Therefore, considering the increasing evidence of the beneficial health effects of adherence to the MD and the ongoing transitions in consumers’ behavior, the present review focuses on updating the scientific knowledge regarding this diet and its relevance to agrobiodiversity. In addition, it also considers a sustainable approach for new marketing opportunities and consumer trends of the MD.

Potato biodiversity: A linear discriminant analysis on the nutritional and physicochemical composition of fifty genotypes

Fifty potato genotypes from twenty-four different countries of origin, four different flesh colours (yellow, purple, red and marble) and different cultivation types (Andean accessions, landraces, breeder lines and cultivated varieties) were studied in terms of their nutritional and physicochemical characteristics. In general, cultivated varieties and breeder lines showed the highest similarity (slight differences only in some particular fatty acids distributions: C10:0, C12:0 and C22:0) concerning the physicochemical parameters assayed in this work, independently of the geographical origin or tuber flesh colour of these genotypes. Nonetheless, some of the studied landraces and Andean accessions proved to be similar enough to be considered as genotypes with good potential for commercial cultivation. These results can contribute to the supply of new potato genotypes into sustainable farming systems, supporting the protection of potato biodiversity, particularly Andean accessions, landraces and coloured genotypes (red or purple flesh) which are not widely cultivated so far.

Metabolites response to onion yellow dwarf virus (OYDV) infection in 'Rossa di Tropea' onion during storage: a 1 H HR-MAS NMR study

BACKGROUND

Plant viral infections induce changes in metabolic components in the host plant, with potential effects on compositional, organoleptic and storability features of agricultural products. Identification of modulated metabolites may provide clues concerning pathways implementing responses in plant-pathogen interactions. A time course study of metabolic fingerprinting of onion yellow dwarf virus (OYDV)-infected versus healthy 'Rossa di Tropea' onion bulbs was performed using proton high-resolution magic angle spinning nuclear magnetic resonance (¹ H HR-MAS NMR) and ultra-performance liquid chromatography (UPLC), providing an overview of the metabolic state of the bulb in response to OYDV infection during storage.

RESULTS

Metabolites accumulated/depleted upon infection were identified, belonging to flavonoid, saccharide, amino acid and organic acid classes. A decrease in quercetin glucosides content and antioxidant activity was observed in infected bulbs; some amino acids (Arg, Asn, Phe, Val) accumulated, while others were depleted (Leu); for some metabolites, a bimodal time-course was observed during storage (Glc, Lys). Virus interference on metabolic pathways, and the effects of the metabolic shift on edible product storability, organoleptic and nutritional quality were discussed.

CONCLUSIONS

OYDV infection induces a metabolic shift in 'Rossa di Tropea' onion during bulb storage, involving several pathways and affecting storability and organoleptic and nutritional quality of bulbs at marketable stage. © 2020 Society of Chemical Industry.

Effect of γ-radiation on post-harvest storage life and quality of onion bulb under ambient condition

Different doses of gamma Irradiation (0 Gy, 10 Gy, 60 Gy, 100 Gy and 200 Gy) were evaluated as potential treatment to extend the storage period and maintain the quality attributes of onion bulbs (cv. Punjab Noraya) at ambient temperature for a period of 144 days. It was observed that storage parameters such as physiological loss in weight, sprouting percentage, rotting percentage and quality traits like total soluble solids, firmness, color parameters, ascorbic acid and pyruvic acid varied significantly (p < 0.05) during storage period with respect to doses of irradiation. No rotting and sprouting were observed upto 24 days and 84 days, respectively in both gamma irradiated and un-irradiated bulbs. At 5 months of storage, the physiological loss in weight varied from 28.5 to 63.6% in all treatments. Physiological weight loss and rotting percentage were higher in the untreated (control) as well as bulbs radiated @ 10 Gy and 200 Gy. Firmness was better retained in the bulbs irradiated with gamma rays @ 120 Gy bulbs upto 84 days of storage. However, no clear-cut pattern for colour changes (L, a, b values) was observed with respect to the irradiation doses. TSS in bulbs decreased upto 36 days of storage and thereafter increased upto 48th day of storage irrespective of the dose of gamma irradiation. Ascorbic acid content of bulbs decreases significantly in all the irradiation treatments during storage but pyruvic acid initially increased, then decreased and again increased at the end of the storage period in un-irradiated and irradiated treatments. It is concluded that onion bulbs irradiated with gamma rays @ 120 Gy resulted in minimum loss in weight, rotting and sprouting while maintained best quality for 3 months of storage at ambient storage conditions.

Metabolite profiling of onion landraces and the cold storage effect

Today, commercial onion breeders focus almost entirely on conventional farming which reduces diversity in the market and leads to loss of desirable traits such as those that impact nutritional and sensory aspects of onions. A way to preserve phenotypic and genetic diversity is to re-evaluate traditional landraces to introduce their benefits to the broader public. Common onion genotypes vary greatly in their storability. In particular, temperature and relative humidity during storage have significant impact on the metabolites in onions after storage. The aim of this study was to assess changes in the metabolite profile of ten onion genotypes after five months of cold storage. In addition, a characterization of onion landraces in their fresh state was also conducted in order to compare their properties against a commercial genotype. Onion genotypes were grown under organic farming conditions. After harvest and curing, bulbs were stored for up to 22 weeks. Before and after storage, bulb samples were analyzed through targeted and untargeted methods. Out of 189 identified metabolites, 128 showed a storage effect. Mainly fructans decreased because of respiration and energy demand, while monosaccharides increased. Further, amino acids were altered in their concentration after storage with an effect on aroma precursors. Eight of the nine landraces had good storability without critical losses. In their fresh state, the onion genotypes clustered into three major groups. For instance, landraces of group III showed consistently and substantially higher levels of amino acids and certain sugars, indicating a high potential of aromatic properties in those onion landraces.

Effect of storage, food processing and novel extraction technologies on onions flavonoid content: A review

Onions play an important part in the daily diet for most populations around the world owing to their nutritional composition and their unique capacity to naturally flavor dishes. Onions contain quercetin and its derivatives - the predominant flavonoid in onions that exert a great contribution to the effective bioactive properties of onion, including its derived products. The present paper comprehensively reviewed flavonoids (with a specific focus on quercetin in onions): their chemical composition, distribution, bioactivities in onion, and impacting factors with a focus on how they can be affected by various post-harvest conditions (storage and food processing). In addition, research on the extraction of flavonoid compounds from onions using a number of novel technologies was also reviewed.

Online measurement of temperature and relative humidity as marker tools for quality changes in onion bulbs during storage

A long shelf life of onions (Allium cepa L.) is of high importance in the onion industry. Onions are dried and stored in large wooden boxes that are difficult to access. Monitoring temperature and relative humidity during these processes is challenging. Moreover, quality may change in storage without being noticed. Therefore, there is a need to find alternative methods for monitoring and controlling the drying and storage processes of onions and to identify early changes in quality during storage. The potential use of online measurements of temperature and relative humidity (RH) in the vicinity of onions was evaluated during drying and long-term storage of six onion batches (four cultivars and three selections of one of the cultivars) in commercial storage. The batches varied in bulb weight, dry matter content, firmness and disease incidence. The dry matter content and firmness decreased during storage, while the respiration rate and incidences of individual and total disease increased. Two of the batches had low storability with high disease incidences and high average temperatures and variations in the RH. The results showed that tracking the temperature and RH in the vicinity of the onions is a promising tool for improving the drying and storage processes in commercial storage and for identifying onion batches with reduced storability early in storage.

Effect of controlled atmospheres on the quality of white onion (Allium cepa L)

Onion is one of the oldest and most consumed crops in the world. Its quality deteriorates gradually during prolonged storage. In the present study, white onions of the variety "Sierra Blanca" were stored in a controlled atmosphere (CA) for 7 months. The color, total pungency, microbiological load and total carbohydrates were evaluated. Three treatments were applied: control treatment (CT), regular atmosphere at 2.5 °C without controlled relative humidity (RH); (T1)1% O₂ + 1% CO₂ at 2.5 °C and 60-75% RH and (T2)3% O₂ + 5% CO₂ at 2.5 °C and 60-75% RH. The statistical analysis showed a significant effect of the treatments and storage time in most of the variables analyzed. The CA managed to preserve the quality of the onion during the storage period while the control bulbs exhibited greater deterioration. These increased 2.9 times their level of pungency, had a higher microbial load and showed a very noticeable color change at the end of storage with respect to freshly harvested onions and those stored in a CA. They had a more yellow-green coloration. Both CA treatments were effective in preserving onion quality, but a more positive effect for T1 than T2 was observed on most of the parameters evaluated.

Valorization of onion solid waste and their flavonols for assessment of cytotoxicity, enzyme inhibitory and antioxidant activities

Onion (Allium cepa L.) is rich with flavonols which perceived benefits to human health. Flavonols like quercetin and quercetin glycosides from onion solid waste (OSW) have been extracted and tested against enzymes of clinical importance in Alzheimer's disease and diabetes and be shown to have cytotoxic and antioxidant effects. A simple high-performance liquid chromatography-diode array detector method using a Zorbax Eclipse XDB C18 column was developed to separate quercetin-3, 4'-O-diglucoside, quercetin-4'-O-monoglucoside, and quercetin from OSW. These compounds were identified using infrared, ultra-violet, ¹H, and ¹³C nuclear magnetic resonance spectroscopic techniques. The OSW solvent fractions and flavonols showed significant antioxidant activities using DPPH (1, 1-diphenyl-2-picrylhydrazyl), FRAP (ferric reducing antioxidant power), and ABTS (2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid) radical scavenging assays. The samples exhibited significant in vitro anti-cholinesterase activity with strong antidiabetic effects. OSW extracted with methanol and ethanol showed greater in vitro anti-cholinesterase and hypoglycemic effects than QDG, QMG, and Q possibly due to interactions between multiple compounds and/or complex multivariate interactions with other factors in OSW. In addition, cytotoxicity assays showed that OSW and QDG, QMG, and Q could inhibit the proliferation of selected cancer cell lines. Results indicate that OSW and flavonol glycosides are potential antioxidant, antidiabetic, anticancer, and sedative agents.