Changes in polyphenol profile of dried apricots containing SO2 at various concentrations during storage

A Randomized Study on the Effect of Dried Fruit on Acid-Base Balance, Diet Quality, and Markers of Musculoskeletal Health in Community Dwelling Adults

OBJECTIVES

We tested whether 100 g/day of dried fruit (vs. no supplemental fruit control) for 6 months alters 24-hr urinary net acid excretion (NAE), bone resorption, weight, body composition, muscle performance, and diet quality. We explored consistency of self-selected dietary composition and potential renal acid load (PRAL).

METHODS

This randomized, single-blind, 2-armed study included 83 normal- and over-weight men and postmenopausal women (age ≥50 years) on self-reported low fruit diets. Endpoints included group differences in NAE (primary), 24-hr urinary N-telopeptide (NTX), weight, body composition, muscle performance, and diet quality.

RESULTS

At baseline, mean (±SD) age was 69 ± 8 years; 86% were Caucasian; body mass index was 24.5 ± 2.8 kg/m²; 46% female, and NAE was 32.4 ± 23.1 mmol with no significant baseline group differences. No significant group differences were noted in NAE (primary), NTX, weight, body composition, muscle performance or diet quality at 6 months. In the cohort as a whole, 6-month change in NAE was positively associated with change in NTX, but no significant associations were noted in other outcomes. PRAL on the day of the urine collection was positively associated with NAE. Comparison of two consecutive baseline 24-hr diet recalls revealed wide intra-individual variability in PRAL in self-selected diets in our participants.

CONCLUSION

In this field study of older adults consuming self-selected diets, making one change to the diet by adding 100 g/day of dried fruit (equivalent to 4 servings per day) had no significant impact on NAE when compared to a no supplemental fruit control. This null finding may be attributable to the high day-to-day variability in consumption of foods affecting NAE. Added fruit also had no significant effect on weight, fat, muscle, or bone outcomes over a 6-month period.

From polyphenol to o-quinone: Occurrence, significance, and intervention strategies in foods and health implications

Polyphenol oxidation is a chemical process impairing food freshness and other desirable qualities, which has become a serious problem in fruit and vegetable processing industry. It is crucial to understand the mechanisms involved in these detrimental alterations. o-Quinones are primarily generated by polyphenols with di/tri-phenolic groups through enzymatic oxidation and/or auto-oxidation. They are highly reactive species, which not only readily suffer the attack by nucleophiles but also powerfully oxidize other molecules presenting lower redox potentials via electron transfer reactions. These reactions and subsequent complicated reactions are capable of initiating quality losses in foods, such as browning, aroma loss, and nutritional decline. To attenuate these adverse influences, a variety of technologies have emerged to restrain polyphenol oxidation via governing different factors, especially polyphenol oxidases and oxygen. Despite tremendous efforts devoted, to date, the loss of food quality caused by quinones has remained a great challenge in the food processing industry. Furthermore, o-quinones are responsible for the chemopreventive effects and/or toxicity of the parent catechols on human health, the mechanisms by which are quite complex. Herein, this review focuses on the generation and reactivity of o-quinones, attempting to clarify mechanisms involved in the quality deterioration of foods and health implications for humans. Potential innovative inhibitors and technologies are also presented to intervene in o-quinone formation and subsequent reactions. In future, the feasibility of these inhibitory strategies should be evaluated, and further exploration on biological targets of o-quinones is of great necessity.

Novel insight into the role of sulfur dioxide in fruits and vegetables: Chemical interactions, biological activity, metabolism, applications, and safety

Sulfur dioxide (SO2) are a category of chemical compounds widely used as additives in food industry. So far, the use of SO2 in fruit and vegetable industry has been indispensable although its safety concerns have been controversial. This article comprehensively reviews the chemical interactions of SO2 with the components of fruit and vegetable products, elaborates its mechanism of antimicrobial, anti-browning, and antioxidation, discusses its roles in regulation of sulfur metabolism, reactive oxygen species (ROS)/redox, resistance induction, and quality maintenance in fruits and vegetables, summarizes the application technology of SO2 and its safety in human (absorption, metabolism, toxicity, regulation), and emphasizes the intrinsic metabolism of SO2 and its consequences for the postharvest physiology and safety of fresh fruits and vegetables. In order to fully understand the benefits and risks of SO2, more research is needed to evaluate the molecular mechanisms of SO2 metabolism in the cells and tissues of fruits and vegetables, and to uncover the interaction mechanisms between SO2 and the components of fruits and vegetables as well as the efficacy and safety of bound SO2. This review has important guiding significance for adjusting an applicable definition of maximum residue limit of SO2 in food.

Properties of Dried Apricots Pretreated by Ultrasound-Assisted Osmotic Dehydration and Application of Active Coatings

Research background

The worldwide demand for healthy and sulphur-free dried vegetables and fruits has grown. Combined ultrasound-assisted osmotic dehydration (UOD) and application of active coatings incorporating natural preservatives represents an attractive alternative to sulphuring to preserve the sensorial and nutritional quality of dried fruits. The aim of this study is to investigate the effect of osmotic dehydration (OD) and UOD, and the use of pectin coatings (alone or with citric acid or ascorbic acid) on physical, textural and microstructural properties of hot air-dried apricots.

Experimental approach

Fresh apricot cubes (1 cm³) were pretreated with either OD at 55 °C for 30 and 45 min or UOD at two ultrasonic frequencies of 25 and 35 kHz for 30 and 45 min followed by application of active coatings with pectin alone, pectin with citric acid or pectin with ascorbic acid for 10 min. All pretreated coated samples were then hot air-dried at 60 °C until a final moisture content of 20% (wet basis) was reached. Physical (shrinkage, apparent and bulk densities), chemical (browning value and water activity) and textural properties (firmness and shrinkage), microstructure and microbial load of dried apricots were studied.

Results and conclusions

Application of OD and UOD improved physical and textural properties of the dried apricots. Moreover, apparent and bulk densities, rehydration capacity of OD and UOD pre-treated samples increased, while shrinkage, water activity and microbial load decreased. Firmness of UOD pretreated samples was significantly (p<0.05) lower than that of OD ones. Likewise, increasing ultrasound frequency from 25 to 35 kHz led to a significant decrease in F_max values of dried apricots. Furthermore, coating of the processed samples with pectin and citric acid increased F_max value and decreased rehydration capacity of dried apricots. Scanning electron microscopy of both OD and UOD samples illustrated improvement of textural properties. The utilization of both OD pretreatment and edible pectin coatings resulted in a decrease in browning values. However, UOD increased browning values of the dried apricots. Coating of UOD samples with pectin and ascorbic acid resulted in substantial discolouration in hot air-dried apricots.

Novelty and scientific contribution

This study advances the knowledge in the field of fruit drying by combined application of OD or UOD pretreatments with active edible coatings on different properties of hot air-dried apricots.

Effect of pulsed electric fields (PEF) on physico-chemical properties, β-carotene and antioxidant activity of air-dried apricots

Fresh apricots pre-treated by pulsed electric fields at different intensities [LPEF, 0.65 kV/cm, 100 Hz, 20 µs and total treatment time 30 s; HPEF1, 1.25 kV/cm, 100 Hz, 20 µs and total treatment time 30 s; HPEF2, 1.25 kV/cm, 100 Hz, 20 µs and total treatment time 60 s], along with controls [non-treated, non-treated and sulphite treated, and heat pre-treatment at 80 °C, for 10 min (HC)] and soaked in 0.2% sodium sulphite solution for 1 h and then were subject to hot air drying. The changes in drying rate, polyphenol oxidase, peroxidase, and β-carotene contents as well as antioxidant activity and colour in pre-treatment and hot air-dried apricot samples were investigated. PEF and heat treatments increased the drying rate of apricots. PEF treatments had no effect on the PPO activity and decreased the POD activity (p < 0.05). HPEF2 treatment retained more β-carotene, higher antioxidant activity and suffered less browning during processing. Overall, the results indicate that combining sulphite treatment with PEF produces dried apricots with more β-carotene and antioxidant activity, and better colour.

Effect of SO2 on sugars, indicators of Maillard reaction, and browning in dried apricots during storage

BACKGROUND

The effect of sulfur dioxide (SO₂ ) concentration was determined on sugars and indicators in the Maillard reaction (MR), and on browning, in sulfured, dried apricots (SDAs) during storage at 4, 20 and 30 °C for 379 days.

RESULTS

As SO₂ concentration increased, the content of reducing sugars involved in the MR also increased. The preventive effect of SO₂ on the MR could not result from the binding of SO₂ to reducing sugars. Before storage, furosine was detected in the non-SDAs but 5-hydroxymethylfurfural (HMF) was not detected. Even the lowest SO₂ concentration (451 mg kg^-1 ) was sufficient to prevent the formation of furosine and HMF during drying of apricots.

CONCLUSION

Formation of furosine and HMF in all samples during storage at 20 and 30 °C for 379 days indicated that SO₂ could not prevent the first and intermediate stages of MR in SDAs during storage. Thus, the main prevention effect of SO₂ on browning in SDAs occurred during drying, not storage. © 2018 Society of Chemical Industry.