2.1.3. Texture

Fruit firmness is one of the leading quality attributes of texture and has an essential commercial impact for both exporters and consumers [54]. In this sense, firmness should be a key goal of breeding in Patagonian soft berries. Strawberry is one of the softest fruits, and loss of firmness is well-documented as being related to cell wall disassembly during ripening [55]. Most significant decreases in cell wall polymers associated with Chilean strawberry fruit ripening occur within the pectin fractions, especially in the covalently bound pectin fraction, which is highly correlated with firmness loss and an increase in the activity of specific cell wall-related enzymes, such as beta-galactosidase [55]. It was reported that the modified atmosphere packaging (MAP) of Chilean strawberry during 12 days of storage at 4 ◦C delayed the fruit dehydration and the firmness loss, that allow the preservation of quality parameters and anthocyanin compounds compare to fruit storage in the control conditions [56]. However, the application of MAP technology diminished the relative abundance of total volatile compounds [56]. In the arrayán berry, a significant reduction in fruit firmness was observed between rounded purple and black ripe stages [21], although this loss in firmness is slower than that observed during the fruit development of *F. chiloensis* [31]. The firmness reduction of *L. apiculata* fruit [21] showed similar values and trends reported for blueberry fruit [57]. A comparative study of postharvest in the two varieties of murta (i.e., South Pearl INIA and Red Pearl INIA) showed that Red Pearl INIA has a major shelf life during 35 days of storage at 0 ◦C [58]. The postharvest assay showed a storage capacity of South Pearl INIA during 20 days at 0 ◦C, while Red Pearl INIA showed major potential for post-harvesting [59]. During treatment of a controlled atmosphere (CA), Red Pearl INIA was stored without problems until 35 days, while South Pearl INIA showed storability until 25 days [59].

## *2.2. Antioxidant Capacity*

In plants, phenolic compounds are produced as secondary metabolites exerting various protective roles and are generally involved in the defense against stress conditions [60–63]. The main phenolic compounds in these fruits can be divided into phenolic acids, and flavonoids such as flavonols, flavanols, and anthocyanins (Figure 2) [62,63]. These molecules are responsible for the major organoleptic characteristics of plant food, such as the visual appearance, flavor, bitterness, astringency, and aroma [64]. Many beneficial effects attributed to phenolic compounds [64–67] have given rise to a new interest in finding plant species with a high phenolic content and relevant biological activity. Studies on the phenolic compounds of the fruits of maqui, murta, calafate, arrayán, and Chilean strawberry highlight the high antioxidant activity they present [15–23] (Table 2). In the following section, we briefly summarize the available literature on the main phenolic compounds described for the Patagonian berries analyzed in this review (Table 2).

**Figure 2.** Polyphenols compounds described in vegetables and fruits. Different phenolic compounds have been reported in native Chilean berries, including phenolic acid, flavonoids such as quercetins—principally quercetin glycosides—and anthocyanins [15–23]. More details are presented in the text. Chemical structures credits [68].


**Table 2.** Antioxidant information of Patagonian berries.

The table shows the available data concerning the antioxidant capacity determined by oxygen-radical absorbing capacity (ORAC) (μmol·100 gDW−1), total polyphenols compounds content (mg GAE gDW−1), and polyphenol compounds reported in these fruits. N.R.: not reported. (\*) polyphenols compounds reported in *F. chiloensis* ssp. *chiloensis* f. chiloensis and reported in (\*\*) *Fragaria chiloensis* ssp. *chiloensis* f. patagonica. More details are given in the text. a DW, dry weight; GAE, gallic acid equivalents.

#### *Foods* **2019**, *8*, 289

Di fferent methods have been used for determining the total antioxidants in di fferent vegetables and fruit, including Patagonian berries. Currently, the oxygen-radical absorbing capacity (ORAC) is a method commonly used to compare the antioxidant capacity in di fferent foods [11,73]. The ORAC values (as μmol per 100 g of dry weight, DW) of maqui (37,174), calafate (72,425), murta (43,574), and arrayan (62,500) berries were reported as being higher than in commercial berries such as raspberries, blueberries (*Vaccinium corymbosum* 'Bluegold') (27,412), and blackberries cultivated in Chile [11,21,69]. Similar trends were reported using di fferent methods [20]. The Trolox equivalent (TE) antioxidant capacity (TEAC) showed that maqui (88.1) and calafate (74.5) had a higher antioxidant capacity (μmol TE per gram of fresh weight, FW) compared to murta (11.7) and blueberry (14.5) fruits [20]. The analysis by 2,2-diphenylpicrylhydrazyl (DPPH) methods showed that the antioxidant activity (mg of crude extract per liter) was higher in maqui (399.8) than in murta (82.9) [15]. The IC50 range of maqui extract (0.0012 and 0.0019 g <sup>L</sup>−1) compared to the average value (0.03 g <sup>L</sup>−1) of commercial berries cultivated in Chile, such as blueberry (*V. corymbosum*), strawberry (*F.* x *ananassa*), and raspberry *(Rubus idaeus*), indicates that a minor concentration of maqui extract is required to inhibit DPPH radicals [74,75]. The above information represents a fundamental background supporting the idea that the Patagonian berries have good potential as a functional food, by themselves or as food ingredients.

#### 2.2.1. Phenolic Content and Composition

The phenolic compounds reported in native Chilean berries include ca ffeic acid, ferulic acid, gallic acid, myricetin, p-coumaric acid, and others [15–23]. Similar to what has been observed for the antioxidant capacity, high total polyphenols contents (TPC) were found for maqui and calafate [19,20]. The di fferent reports of total phenolic analysis using the Folin–Ciocalteu method showed di fferent rankings for Patagonian berries. The first studies showed a higher total phenol content (as μmol gallic acid equivalents (GAE) per gram of FW) for maqui (97 μmol GAE g<sup>−</sup><sup>1</sup> FW) and calafate (87 μmol GAE g<sup>−</sup><sup>1</sup> FW), followed by murta (32 μmol GAE g<sup>−</sup><sup>1</sup> FW) compared to blueberry (17 μmol GAE g<sup>−</sup><sup>1</sup> FW) [20]. Some reports showed similar values of the total polyphenols content (as mg GAE per gram of DW) for calafate (33.9 mg GAE g<sup>−</sup><sup>1</sup> DW), maqui (31.2 mg GAE g<sup>−</sup><sup>1</sup> DW) and murta (34.,9 mg GAE g<sup>−</sup><sup>1</sup> DW) [11], while other reports indicated significant di fferences between Patagonian berries, with higher values for calafate (65.5 mg GAE g<sup>−</sup><sup>1</sup> DW), followed by arrayán (27.6 mg GAE g<sup>−</sup><sup>1</sup> DW), and lower values for murta (9.2 mg GAE g<sup>−</sup><sup>1</sup> DW) [19].

Concerning the polyphenols composition of the Patagonian berries, maqui and calafate showed anthocyanin as the main component, while fruits of the Myrtaceae family (e.g., murta and arrayán) showed a higher content of flavonoid compounds [15,16,18–21,70–72]. Calafate fruit showed a comparable flavonoid content (0.16 μmol g<sup>−</sup><sup>1</sup> FW) to that obtained for maqui fruit (0.12 μmol g<sup>−</sup><sup>1</sup> FW) [20]. In calafate berry collected from di fferent localities, the identification of flavonoids and phenolic acids showed a higher content of rutin, gallic-chlorogenic, and ca ffeic acid, and the presence of coumaric and ferulic acid, quercetin, myricetin, and kaempferol [20,76].

The multiple bioactive compounds of the maqui berry (i.e., phenolic antioxidants, alkaloids, flavonoids, and particularly anthocyanins) have contributed to knowledge of the functional potential of this berry in several countries [38,77–79]. An HPLC analysis of maqui berry extracts showed 10 compounds identified as flavonols and ellagic acid [70]. The non-anthocyanin compounds were mainly quercetin and its derivatives (with the highest concentration of dimethoxy-quercetin, followed by rutin (quercetin-3-rutinoside) and quercetin-3-galactoside), myricetin and its derivatives, and an important content of ellagic acid [70].

In arrayán, the polyphenol compounds identified mainly correspond to flavonols such as quercetin 3-rutinoside and its derivates, tannins and their monomers, and a minor number of anthocyanins [18,21]. In murta, ca ffeic acid-3-glucoside, quercetin-3-glucoside, and quercetin were reported as three major compounds in ethanolic extracts of fruit, and the others compounds were gallic acid, rutin, quercitrin, luteolin, luteolin-3-glucoside, kaempferol, kaempferol-3-glucoside, myricetin, and *p*-coumaric acid [72].

In the Chilean strawberry species, several compounds were identified, including an ellagic acid-based compound, catechin, and flavonol derivatives. The higher content of non-anthocyanins identified in *F. chiloensis* and *F.* x *ananassa* 'Chandler' were ellagic acid and their pentoside and rhamnoside derivatives and quercetin glucuronide [17]. On the other hand, ellagitannin, quercetin pentoside, and kaempferol glucuronide were only reported in *F. chiloensis* and some compounds—catechin, quercetin pentoside, and quercetin hexoside—were only reported in *Fragaria chiloensis* ssp. *chiloensis* f. chiloensis, and other compounds—procyanidin tetramers and ellagitannin—were only reported in *F. chiloensis* ssp. *chiloensis* f. patagonica [17].
