Acorns as a Food Resource. An Experiment with Acorn Preparation and Taste

this paper summarizes our current knowledge of acorns as a food resource in prehistoric europe. It sheds light on the question of the taste of acorn products, which is closely linked to preparation methods. an experiment was conducted that consisted of the preparation of eight different acorn recipes, human tasters, a questionnaire-based survey, and statistical evaluation. the paper presents the various factors that testers indicated had an effect on the taste of differently prepared acorn products. IANSA 2011 ● II/2 ● 139–147 Tereza Šálková, Michaela Divišová, Štěpánka Kadochová, Jiří Beneš, Kateřina Delawská, Eva Kadlčková, Lenka Němečková, Kamila Pokorná, Václav Voska, Andrea Žemličková: Acorns as a Food Resource. An Experiment with Acorn Preparation and Taste 140 right conditions acorns may also be stored for long periods (Mason 1995; Cunningham 2011). on the other hand, acorns also contain a high concentration of tannic acid, a mild toxin which gives them a bitter taste. the concentration of tannin varies between oak species and even between individual trees of one species (Mason 1995). some oak species produce acorns low in tannin and all acorns are edible when properly prepared. tannins can be removed by a variety of methods such as soaking in water, boiling, roasting or even simply burying them in the ground (see Vencl 1985 for further details). Vencl (1996) notes several factors limiting the exploitation of acorns as food. First, individual oak species differ in their annual fruit production and acorn taste. oak begins to bear fruit after about 25 years. Even though oak trees usually produce a plentiful crop of acorns, a rich crop does not occur annually, and the interval between good yields varies by species. although this irregularity of availability could be compensated by the durability of acorns and the coexistence of diverse oak species within one area, it can be assumed that this was a factor that limited oak cultivation (Vencl 1996, 95). Both good and poor producers tend to be similarly represented in the fruiting population (greenberg 2000). With regard to central European oaks (Q. robur and Q. petraea), which go through a 2 to 6 year cycle, Karg and haas have suggested that these could have been managed in prehistory in order to increase the availability of nutrient resources and consequently to enlarge the yields (Karg, Haas 1996). Another factor limiting acorn exploitation for food includes the amount of work involved in preparation. acorns were also exploited by past communities for many other reasons. they were consumed in the form of bread, soups, porridge, or as a coffee substitute right up to modern times (Rakić et al. 2006). Since acorns are also a source of food for many domestic animal species, the occurrence of acorns in archaeological contexts may result from their use as livestock fodder (Vencl 1996, 96–97). The use of acorrns for pig food has also been well documented since medieval times (Le Goff 1991). It should also be mentioned that acorns could be used for the processing of animal hides or dyeing (Vencl 1985). With respect to medicine it has been reported that oak acorns can be used to reduce urination, treat wound and inflammation, stop bleeding and to treat kidney stones (Lev, Amar 2000; Lev 2002). 1.3 Acorns in prehistory In evaluating the evidence for acorn use by ancient communities, we need to consider several issues. First, one should bear in mind that the recovery of plant remains depends on harvesting and processing methods, preservation conditions, and method of retrieval (Dennel 1976). In the case of acorns, poor preservation results from certain processing techniques, due to carbonization which usually destroys the thin-walled shells (lev et al. 2005). Additionally, the manner and location of acorn processing may have been undertaken completely or partially off site (lev et al. 2005). Moreover, a limited use of flotation techniques in Europe and significant national and regional differences in the intensity of archaeobotanical research (Vencl 1985; Mason 1995), result in an underestimation of acorns as a source of human nutrition in the past. on the other hand, it needs to be stressed that recent research has put acorns as food into a new perspective. currently, there is no doubt about the extensive use of acorns as food in prehistory (e.g. Vencl 1985; 1996; Mason 1992; 1995; Karg, Haas 1996; Kubiak-Martens 1999; Bouby et al. 1999; lev et al. 2005). to summarize, acorns are a food resource that could have played an important role in prehistoric human subsistence in Europe. As already stated, finds of charred acorns are not exceptional, and occur from the Mesolithic through to modern times throughout europe. a considerable body of research indicates that acorns were used both occasionally in emergencies and systemically. the archaeological record, however, does not resolve whether the individual acorn finds represent a staple or sporadic food resource (Vencl 1985, 552). acorn use has been widely investigated ethnographically, including a well-known ethnographic study of acorns use for human consumption in prehistoric california (e.g. Mason 1992). Aside from ethnographic research, finds of charred acorns in archaeological contexts have been examined and discussed by several authors (see for instance Vencl 1985, 1996; Mason 1992; De Hingh 2000). although plant remains are scare in the palaeolithic, the oldest acorns have been found in a number of palaeolithic sites in the near east (e.g. Kislev et al. 1992; goren-Inbar et al. 2002; aura et al. 2005; Lev et al. 2005). In light of this, it is thought that acorns may have been a staple plant food long before the maximal spread of oak that occurred during the atlantic period (late Mesolithic and neolithic, 8900–5700 BP) (Vencl 1996, 100). During the Mesolithic, finds of concentrations of charred acorns increase (Zvelebil 1994; Vencl 1996; KubiakMartens 1999; aura et al. 2005), in accord with the spread of oak forests, which enabled intensive acorn gathering. Mason (2000) considered the possible role played by fire in the Mesolithic, and from ethnographic and ecological data suggested that fire could have been used to manipulate the acorn supply. this approach to Mesolithic forest burning challenges the traditional view that fire might have been used mainly to improve hunting by improving the productivity and nutritional quality of animal forage, or to attract animals or to improve visibility of animals by reducing their cover (Mason 2000, 139–140). Mason focuses on the manner in which burning contributes to acorn gathering. she posits that burning reduces competition for nutrients etc. from other species, and in so doing provides oak trees with advantages that improve the growth of acorns. In addition, removing ground cover facilitates gathering of acorns. It should be clear at this point that during the pre-agricultural period acorns were an important plant food resource for hunter-gatherers in europe. one should also bear in mind that archaeological evidence supports the conclusion that acorns have always been an attractive food resource within various resource strategies, including agrarian societies. IANSA 2011 ● II/2 ● 139–147 Tereza Šálková, Michaela Divišová, Štěpánka Kadochová, Jiří Beneš, Kateřina Delawská, Eva Kadlčková, Lenka Němečková, Kamila Pokorná, Václav Voska, Andrea Žemličková: Acorns as a Food Resource. An Experiment with Acorn Preparation and Taste 141 According to De Hing (2000, 200–202) acorns in prehistoric agricultural communities may have played a role as food substitute or reserve for bad times, reserved for emergencies, for example when cereal agriculture had failed. Within the context of agricultural sites acorns are usually located close to fireplaces and in furnaces. Frequently they are accompanied by other crops (De Hingh 2000). In addition, acorns are common finds in vessels and storage pits. They are often shelled and mixed with cereals. acorns also occur in shallow pits and are also found unshelled (deforce et al. 2009). Acorns are found in graves, and their appearance there as sacrificial offering cannot be discounted. (Vencl 1985). There is no doubt that there is sufficient evidence for acorn use in human subsistence in prehistory, as shown above. the focus of this article is on the way in which acorns may have been processed to remove their tannins when using them for food. In order to do so we conducted an experiment, described below, the aim of which was to identify how preparation methods affect the final taste of the product. 2. Materials and Methods 2.1 Experiment For our experiment we chose acorns from Quercus robur, which has grown throughout europe since the beginning of the holocene. Q. robur is also reported to have acorns which are relatively low in tannin. this species is a convenient nutritional resource (Rakić et al. 2006). Acorns were collected from several different locations in the region (Figure 1) between September and November 2011. acorns from each site were processed according to the following four methods. subsequent processing include shelling, grinding, roasting and boiling, in various orders, using a modern knife, poppy seed grinder, pan, electric cooker and oven (Table 1). Figure 1. acorn collection sites, south Bohemia: 1 – Chotýčany, 2 – Stříbřec, 3 – Hajská-Strakonice, 4+5 České BudějoviceStromovka; 6+7 – České Budějovice-U Lesa, 8 – Bechyně, 11 – Hartmanice. Table 1. characteristics of eight acorn product samples. sample 1 1. shelling 2. grinding 3. roasting to lose bitterness sample 1a 1. shelling 2. grinding 3. roasting to loose bitterness 4. mixing at 1:1 ratio with wheat flour (triticum aestivum) sample 2 1. shelling 2. boiling in water until soft 3. grinding sample 2a 1. shelling 2. boiling in water until soft 3. grinding 4. mixing at 1:1 ratio with wheat flour (triticum aestivum) sample 3 1. roasting 2. shelling 3. grinding sample 3a 1. roastin